59cd4f435ee972b8fb87d50ea36d76929aabf3a3
36755
Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
 Linus Torvalds
|
b89c07dea1 |
Merge tags 'objtool-urgent-2021-06-28' and 'objtool-core-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull objtool fix and updates from Ingo Molnar: "An ELF format fix for a section flags mismatch bug that breaks kernel tooling such as kpatch-build. The biggest change in this cycle is the new code to handle and rewrite variable sized jump labels - which results in slightly tighter code generation in hot paths, through the use of short(er) NOPs. Also a number of cleanups and fixes, and a change to the generic include/linux/compiler.h to handle a s390 GCC quirk" * tag 'objtool-urgent-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: objtool: Don't make .altinstructions writable * tag 'objtool-core-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: objtool: Improve reloc hash size guestimate instrumentation.h: Avoid using inline asm operand modifiers compiler.h: Avoid using inline asm operand modifiers kbuild: Fix objtool dependency for 'OBJECT_FILES_NON_STANDARD_<obj> := n' objtool: Reflow handle_jump_alt() jump_label/x86: Remove unused JUMP_LABEL_NOP_SIZE jump_label, x86: Allow short NOPs objtool: Provide stats for jump_labels objtool: Rewrite jump_label instructions objtool: Decode jump_entry::key addend jump_label, x86: Emit short JMP jump_label: Free jump_entry::key bit1 for build use jump_label, x86: Add variable length patching support jump_label, x86: Introduce jump_entry_size() jump_label, x86: Improve error when we fail expected text jump_label, x86: Factor out the __jump_table generation jump_label, x86: Strip ASM jump_label support x86, objtool: Dont exclude arch/x86/realmode/ objtool: Rewrite hashtable sizing |
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Daniel Bristot de Oliveira
|
498627b4ac |
trace/osnoise: Fix return value on osnoise_init_hotplug_support
kernel test robot reported:
>> kernel/trace/trace_osnoise.c:1584:2: error: void function
'osnoise_init_hotplug_support' should not return a
value [-Wreturn-type]
return 0;
When !CONFIG_HOTPLUG_CPU.
Fix it problem by removing the return value.
Link: https://lkml.kernel.org/r/c7fc67f1a117cc88bab2e508c898634872795341.1624872608.git.bristot@redhat.com
Fixes:
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Daniel Bristot de Oliveira
|
2a81afa326 |
trace/osnoise: Make interval u64 on osnoise_main
kernel test robot reported:
>> kernel/trace/trace_osnoise.c:966:3: warning: comparison of distinct
pointer types ('typeof ((interval)) *' (aka 'long long *') and
'uint64_t *' (aka 'unsigned long long *'))
[-Wcompare-distinct-pointer-types]
do_div(interval, USEC_PER_MSEC);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
include/asm-generic/div64.h:228:28: note: expanded from macro 'do_div'
(void)(((typeof((n)) *)0) == ((uint64_t *)0)); \
~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~
As interval cannot be negative because sample_period >= sample_runtime,
making interval u64 on osnoise_main() is enough to fix this problem.
Link: https://lkml.kernel.org/r/4ae1e7780563598563de079a3ef6d4d10b5f5546.1624872608.git.bristot@redhat.com
Fixes:
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Daniel Bristot de Oliveira
|
f7d9f6370e |
trace/osnoise: Fix 'no previous prototype' warnings
kernel test robot reported some osnoise functions with "no previous
prototype."
Fix these warnings by making local functions static, and by adding:
void osnoise_trace_irq_entry(int id);
void osnoise_trace_irq_exit(int id, const char *desc);
to include/linux/trace.h.
Link: https://lkml.kernel.org/r/e40d3cb4be8bde921f4b40fa6a095cf85ab807bd.1624872608.git.bristot@redhat.com
Fixes:
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Steven Rostedt (VMware)
|
b96285e10a |
tracing: Have osnoise_main() add a quiescent state for task rcu
ftracetest triggered:
INFO: rcu_tasks detected stalls on tasks:
00000000b92b832d: .. nvcsw: 1/1 holdout: 1 idle_cpu: -1/7
task:osnoise/7 state:R running task stack: 0 pid: 2133 ppid: 2 flags:0x00004000
Call Trace:
? asm_sysvec_apic_timer_interrupt+0x12/0x20
? asm_sysvec_apic_timer_interrupt+0x12/0x20
? trace_hardirqs_on+0x2b/0xe0
? asm_sysvec_apic_timer_interrupt+0x12/0x20
? trace_clock_local+0xc/0x20
? osnoise_main+0x10e/0x450
? trace_softirq_entry_callback+0x50/0x50
? kthread+0x153/0x170
? __kthread_bind_mask+0x60/0x60
? ret_from_fork+0x22/0x30
While running osnoise tracer with other tracers that rely on
synchronize_rcu_tasks(), where that just hung.
The reason is that osnoise_main() never schedules out if the interval
is less than 1, and this will cause synchronize_rcu_tasks() to never
return.
Link: https://lkml.kernel.org/r/20210628114953.6dc06a91@oasis.local.home
Fixes:
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Linus Torvalds
|
c10383b3fb |
Merge tag 'regulator-v5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regulator
Pull regulator updates from Mark Brown:
"The main core change this release is generic support for handling of
hardware errors from Matti Vaittinen, including some small updates to
the reboot and thermal code so we can share support for powering off
the system if things are going wrong enough.
Otherwise this release we've mainly seen the addition of new drivers,
including MT6359 which has pulled in some small changes from the MFD
tree for build dependencies.
- Support for controlling the trigger points for hardware error
detection, and shared handlers for this.
- Support for Maxim MAX8993, Mediatek MT6359 and MT6359P, Qualcomm
PM8226 and SA8115P-ADP, and Sylergy TCS4526"
* tag 'regulator-v5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regulator: (91 commits)
regulator: bd9576: Fix uninitializes variable may_have_irqs
regulator: max8893: Select REGMAP_I2C to fix build error
regulator: da9052: Ensure enough delay time for .set_voltage_time_sel
regulator: mt6358: Fix vdram2 .vsel_mask
regulator: hi6421v600: Fix setting wrong driver_data
MAINTAINERS: Add reviewer for regulator irq_helpers
regulator: bd9576: Fix the driver name in id table
regulator: bd9576: Support error reporting
regulator: bd9576 add FET ON-resistance for OCW
regulator: add property parsing and callbacks to set protection limits
regulator: IRQ based event/error notification helpers
regulator: move rdev_print helpers to internal.h
regulator: add warning flags
thermal: Use generic HW-protection shutdown API
reboot: Add hardware protection power-off
regulator: Add protection limit properties
regulator: hi6421v600: Fix setting idle mode
regulator: Add MAX8893 bindings
regulator: max8893: add regulator driver
regulator: hi6421: Use correct variable type for regmap api val argument
...
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Rustam Kovhaev
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ccff81e1d0 |
bpf: Fix false positive kmemleak report in bpf_ringbuf_area_alloc()
kmemleak scans struct page, but it does not scan the page content. If we
allocate some memory with kmalloc(), then allocate page with alloc_page(),
and if we put kmalloc pointer somewhere inside that page, kmemleak will
report kmalloc pointer as a false positive.
We can instruct kmemleak to scan the memory area by calling kmemleak_alloc()
and kmemleak_free(), but part of struct bpf_ringbuf is mmaped to user space,
and if struct bpf_ringbuf changes we would have to revisit and review size
argument in kmemleak_alloc(), because we do not want kmemleak to scan the
user space memory. Let's simplify things and use kmemleak_not_leak() here.
For posterity, also adding additional prior analysis from Andrii:
I think either kmemleak or syzbot are misreporting this. I've added a
bunch of printks around all allocations performed by BPF ringbuf. [...]
On repro side I get these two warnings:
[vmuser@archvm bpf]$ sudo ./repro
BUG: memory leak
unreferenced object 0xffff88810d538c00 (size 64):
comm "repro", pid 2140, jiffies 4294692933 (age 14.540s)
hex dump (first 32 bytes):
00 af 19 04 00 ea ff ff c0 ae 19 04 00 ea ff ff ................
80 ae 19 04 00 ea ff ff c0 29 2e 04 00 ea ff ff .........)......
backtrace:
[<0000000077bfbfbd>] __bpf_map_area_alloc+0x31/0xc0
[<00000000587fa522>] ringbuf_map_alloc.cold.4+0x48/0x218
[<0000000044d49e96>] __do_sys_bpf+0x359/0x1d90
[<00000000f601d565>] do_syscall_64+0x2d/0x40
[<0000000043d3112a>] entry_SYSCALL_64_after_hwframe+0x44/0xae
BUG: memory leak
unreferenced object 0xffff88810d538c80 (size 64):
comm "repro", pid 2143, jiffies 4294699025 (age 8.448s)
hex dump (first 32 bytes):
80 aa 19 04 00 ea ff ff 00 ab 19 04 00 ea ff ff ................
c0 ab 19 04 00 ea ff ff 80 44 28 04 00 ea ff ff .........D(.....
backtrace:
[<0000000077bfbfbd>] __bpf_map_area_alloc+0x31/0xc0
[<00000000587fa522>] ringbuf_map_alloc.cold.4+0x48/0x218
[<0000000044d49e96>] __do_sys_bpf+0x359/0x1d90
[<00000000f601d565>] do_syscall_64+0x2d/0x40
[<0000000043d3112a>] entry_SYSCALL_64_after_hwframe+0x44/0xae
Note that both reported leaks (ffff88810d538c80 and ffff88810d538c00)
correspond to pages array bpf_ringbuf is allocating and tracking properly
internally. Note also that syzbot repro doesn't close FD of created BPF
ringbufs, and even when ./repro itself exits with error, there are still
two forked processes hanging around in my system. So clearly ringbuf maps
are alive at that point. So reporting any memory leak looks weird at that
point, because that memory is being used by active referenced BPF ringbuf.
It's also a question why repro doesn't clean up its forks. But if I do a
`pkill repro`, I do see that all the allocated memory is /properly/ cleaned
up [and the] "leaks" are deallocated properly.
BTW, if I add close() right after bpf() syscall in syzbot repro, I see that
everything is immediately deallocated, like designed. And no memory leak
is reported. So I don't think the problem is anywhere in bpf_ringbuf code,
rather in the leak detection and/or repro itself.
Reported-by: syzbot+5d895828587f49e7fe9b@syzkaller.appspotmail.com
Signed-off-by: Rustam Kovhaev <rkovhaev@gmail.com>
[ Daniel: also included analysis from Andrii to the commit log ]
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: syzbot+5d895828587f49e7fe9b@syzkaller.appspotmail.com
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/CAEf4BzYk+dqs+jwu6VKXP-RttcTEGFe+ySTGWT9CRNkagDiJVA@mail.gmail.com
Link: https://lore.kernel.org/lkml/YNTAqiE7CWJhOK2M@nuc10
Link: https://lore.kernel.org/lkml/20210615101515.GC26027@arm.com
Link: https://syzkaller.appspot.com/bug?extid=5d895828587f49e7fe9b
Link: https://lore.kernel.org/bpf/20210626181156.1873604-1-rkovhaev@gmail.com
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Namhyung Kim
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95b861a793 |
bpf: Allow bpf_get_current_ancestor_cgroup_id for tracing
Allow the helper to be called from tracing programs. This is needed to handle cgroup hiererachies in the program. Signed-off-by: Namhyung Kim <namhyung@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20210627153627.824198-1-namhyung@kernel.org |
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Odin Ugedal
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1c35b07e6d |
sched/fair: Ensure _sum and _avg values stay consistent
The _sum and _avg values are in general sync together with the PELT divider. They are however not always completely in perfect sync, resulting in situations where _sum gets to zero while _avg stays positive. Such situations are undesirable. This comes from the fact that PELT will increase period_contrib, also increasing the PELT divider, without updating _sum and _avg values to stay in perfect sync where (_sum == _avg * divider). However, such PELT change will never lower _sum, making it impossible to end up in a situation where _sum is zero and _avg is not. Therefore, we need to ensure that when subtracting load outside PELT, that when _sum is zero, _avg is also set to zero. This occurs when (_sum < _avg * divider), and the subtracted (_avg * divider) is bigger or equal to the current _sum, while the subtracted _avg is smaller than the current _avg. Reported-by: Sachin Sant <sachinp@linux.vnet.ibm.com> Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org> Signed-off-by: Odin Ugedal <odin@uged.al> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Tested-by: Sachin Sant <sachinp@linux.vnet.ibm.com> Link: https://lore.kernel.org/r/20210624111815.57937-1-odin@uged.al |
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Randy Dunlap
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0e3c1f30b0 |
genirq/irqdesc: Drop excess kernel-doc entry @lookup
Fix kernel-doc warning in irqdesc.c:
../kernel/irq/irqdesc.c:692: warning: Excess function parameter 'lookup' description in 'handle_domain_irq'
Fixes:
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Thomas Gleixner
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3d2ce675ab |
Merge tag 'irqchip-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms into irq/core
Pull irqchip updates from Marc Zyngier: - Revamped the irqdomain internals to consistently cache irqdata - Expose a new API to simplify IRQ handling involving an irqdomain by not using the IRQ number - Convert all the irqchip drivers to this new API - Allow the Qualcomm PDC driver to be compiled as a module - Fix HiSi MBIGEN compile warning when CONFIG_ACPI isn't selected - Remove a bunch of spurious printks on error paths - The obligatory couple of DT updates |
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Thomas Gleixner
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2d0a9eb23c |
time/kunit: Add missing MODULE_LICENSE()
[ mingo: MODULE_LICENSE() takes a string. ] Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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Linus Torvalds
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b4b27b9eed |
Revert "signal: Allow tasks to cache one sigqueue struct"
This reverts commits |
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Daniel Bristot de Oliveira
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c8895e271f |
trace/osnoise: Support hotplug operations
Enable and disable osnoise/timerlat thread during on CPU hotplug online and offline operations respectivelly. Link: https://lore.kernel.org/linux-doc/20210621134636.5b332226@oasis.local.home/ Link: https://lkml.kernel.org/r/39f98590b3caeb3c32f09526214058efe0e9272a.1624372313.git.bristot@redhat.com Cc: Phil Auld <pauld@redhat.com> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Kate Carcia <kcarcia@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Alexandre Chartre <alexandre.chartre@oracle.com> Cc: Clark Willaims <williams@redhat.com> Cc: John Kacur <jkacur@redhat.com> Cc: Juri Lelli <juri.lelli@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Cc: linux-doc@vger.kernel.org Cc: linux-kernel@vger.kernel.org Suggested-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> |
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Daniel Bristot de Oliveira
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ba998f7d95 |
trace/hwlat: Support hotplug operations
Enable and disable hwlat thread during cpu hotplug online and offline operations, respectivelly. Link: https://lore.kernel.org/linux-doc/20210621134636.5b332226@oasis.local.home/ Link: https://lkml.kernel.org/r/52012d25ea35491a0f8088b947864d8df8e25157.1624372313.git.bristot@redhat.com Cc: Phil Auld <pauld@redhat.com> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Kate Carcia <kcarcia@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Alexandre Chartre <alexandre.chartre@oracle.com> Cc: Clark Willaims <williams@redhat.com> Cc: John Kacur <jkacur@redhat.com> Cc: Juri Lelli <juri.lelli@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Cc: linux-doc@vger.kernel.org Cc: linux-kernel@vger.kernel.org Suggested-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> |
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Daniel Bristot de Oliveira
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039a602db3 |
trace/hwlat: Protect kdata->kthread with get/put_online_cpus
In preparation to the hotplug support, protect kdata->kthread with get/put_online_cpus() to avoid concurrency with hotplug operations. Link: https://lore.kernel.org/linux-doc/20210621134636.5b332226@oasis.local.home/ Link: https://lkml.kernel.org/r/8bdb2a56f46abfd301d6fffbf43448380c09a6f5.1624372313.git.bristot@redhat.com Cc: Phil Auld <pauld@redhat.com> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Kate Carcia <kcarcia@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Alexandre Chartre <alexandre.chartre@oracle.com> Cc: Clark Willaims <williams@redhat.com> Cc: John Kacur <jkacur@redhat.com> Cc: Juri Lelli <juri.lelli@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Cc: linux-doc@vger.kernel.org Cc: linux-kernel@vger.kernel.org Suggested-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> |
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Daniel Bristot de Oliveira
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a955d7eac1 |
trace: Add timerlat tracer
The timerlat tracer aims to help the preemptive kernel developers to
found souces of wakeup latencies of real-time threads. Like cyclictest,
the tracer sets a periodic timer that wakes up a thread. The thread then
computes a *wakeup latency* value as the difference between the *current
time* and the *absolute time* that the timer was set to expire. The main
goal of timerlat is tracing in such a way to help kernel developers.
Usage
Write the ASCII text "timerlat" into the current_tracer file of the
tracing system (generally mounted at /sys/kernel/tracing).
For example:
[root@f32 ~]# cd /sys/kernel/tracing/
[root@f32 tracing]# echo timerlat > current_tracer
It is possible to follow the trace by reading the trace trace file:
[root@f32 tracing]# cat trace
# tracer: timerlat
#
# _-----=> irqs-off
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# || /
# |||| ACTIVATION
# TASK-PID CPU# |||| TIMESTAMP ID CONTEXT LATENCY
# | | | |||| | | | |
<idle>-0 [000] d.h1 54.029328: #1 context irq timer_latency 932 ns
<...>-867 [000] .... 54.029339: #1 context thread timer_latency 11700 ns
<idle>-0 [001] dNh1 54.029346: #1 context irq timer_latency 2833 ns
<...>-868 [001] .... 54.029353: #1 context thread timer_latency 9820 ns
<idle>-0 [000] d.h1 54.030328: #2 context irq timer_latency 769 ns
<...>-867 [000] .... 54.030330: #2 context thread timer_latency 3070 ns
<idle>-0 [001] d.h1 54.030344: #2 context irq timer_latency 935 ns
<...>-868 [001] .... 54.030347: #2 context thread timer_latency 4351 ns
The tracer creates a per-cpu kernel thread with real-time priority that
prints two lines at every activation. The first is the *timer latency*
observed at the *hardirq* context before the activation of the thread.
The second is the *timer latency* observed by the thread, which is the
same level that cyclictest reports. The ACTIVATION ID field
serves to relate the *irq* execution to its respective *thread* execution.
The irq/thread splitting is important to clarify at which context
the unexpected high value is coming from. The *irq* context can be
delayed by hardware related actions, such as SMIs, NMIs, IRQs
or by a thread masking interrupts. Once the timer happens, the delay
can also be influenced by blocking caused by threads. For example, by
postponing the scheduler execution via preempt_disable(), by the
scheduler execution, or by masking interrupts. Threads can
also be delayed by the interference from other threads and IRQs.
The timerlat can also take advantage of the osnoise: traceevents.
For example:
[root@f32 ~]# cd /sys/kernel/tracing/
[root@f32 tracing]# echo timerlat > current_tracer
[root@f32 tracing]# echo osnoise > set_event
[root@f32 tracing]# echo 25 > osnoise/stop_tracing_total_us
[root@f32 tracing]# tail -10 trace
cc1-87882 [005] d..h... 548.771078: #402268 context irq timer_latency 1585 ns
cc1-87882 [005] dNLh1.. 548.771082: irq_noise: local_timer:236 start 548.771077442 duration 4597 ns
cc1-87882 [005] dNLh2.. 548.771083: irq_noise: reschedule:253 start 548.771083017 duration 56 ns
cc1-87882 [005] dNLh2.. 548.771086: irq_noise: call_function_single:251 start 548.771083811 duration 2048 ns
cc1-87882 [005] dNLh2.. 548.771088: irq_noise: call_function_single:251 start 548.771086814 duration 1495 ns
cc1-87882 [005] dNLh2.. 548.771091: irq_noise: call_function_single:251 start 548.771089194 duration 1558 ns
cc1-87882 [005] dNLh2.. 548.771094: irq_noise: call_function_single:251 start 548.771091719 duration 1932 ns
cc1-87882 [005] dNLh2.. 548.771096: irq_noise: call_function_single:251 start 548.771094696 duration 1050 ns
cc1-87882 [005] d...3.. 548.771101: thread_noise: cc1:87882 start 548.771078243 duration 10909 ns
timerlat/5-1035 [005] ....... 548.771103: #402268 context thread timer_latency 25960 ns
For further information see: Documentation/trace/timerlat-tracer.rst
Link: https://lkml.kernel.org/r/71f18efc013e1194bcaea1e54db957de2b19ba62.1624372313.git.bristot@redhat.com
Cc: Phil Auld <pauld@redhat.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Kate Carcia <kcarcia@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Alexandre Chartre <alexandre.chartre@oracle.com>
Cc: Clark Willaims <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
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Daniel Bristot de Oliveira
|
bce29ac9ce |
trace: Add osnoise tracer
In the context of high-performance computing (HPC), the Operating System
Noise (*osnoise*) refers to the interference experienced by an application
due to activities inside the operating system. In the context of Linux,
NMIs, IRQs, SoftIRQs, and any other system thread can cause noise to the
system. Moreover, hardware-related jobs can also cause noise, for example,
via SMIs.
The osnoise tracer leverages the hwlat_detector by running a similar
loop with preemption, SoftIRQs and IRQs enabled, thus allowing all
the sources of *osnoise* during its execution. Using the same approach
of hwlat, osnoise takes note of the entry and exit point of any
source of interferences, increasing a per-cpu interference counter. The
osnoise tracer also saves an interference counter for each source of
interference. The interference counter for NMI, IRQs, SoftIRQs, and
threads is increased anytime the tool observes these interferences' entry
events. When a noise happens without any interference from the operating
system level, the hardware noise counter increases, pointing to a
hardware-related noise. In this way, osnoise can account for any
source of interference. At the end of the period, the osnoise tracer
prints the sum of all noise, the max single noise, the percentage of CPU
available for the thread, and the counters for the noise sources.
Usage
Write the ASCII text "osnoise" into the current_tracer file of the
tracing system (generally mounted at /sys/kernel/tracing).
For example::
[root@f32 ~]# cd /sys/kernel/tracing/
[root@f32 tracing]# echo osnoise > current_tracer
It is possible to follow the trace by reading the trace trace file::
[root@f32 tracing]# cat trace
# tracer: osnoise
#
# _-----=> irqs-off
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth MAX
# || / SINGLE Interference counters:
# |||| RUNTIME NOISE % OF CPU NOISE +-----------------------------+
# TASK-PID CPU# |||| TIMESTAMP IN US IN US AVAILABLE IN US HW NMI IRQ SIRQ THREAD
# | | | |||| | | | | | | | | | |
<...>-859 [000] .... 81.637220: 1000000 190 99.98100 9 18 0 1007 18 1
<...>-860 [001] .... 81.638154: 1000000 656 99.93440 74 23 0 1006 16 3
<...>-861 [002] .... 81.638193: 1000000 5675 99.43250 202 6 0 1013 25 21
<...>-862 [003] .... 81.638242: 1000000 125 99.98750 45 1 0 1011 23 0
<...>-863 [004] .... 81.638260: 1000000 1721 99.82790 168 7 0 1002 49 41
<...>-864 [005] .... 81.638286: 1000000 263 99.97370 57 6 0 1006 26 2
<...>-865 [006] .... 81.638302: 1000000 109 99.98910 21 3 0 1006 18 1
<...>-866 [007] .... 81.638326: 1000000 7816 99.21840 107 8 0 1016 39 19
In addition to the regular trace fields (from TASK-PID to TIMESTAMP), the
tracer prints a message at the end of each period for each CPU that is
running an osnoise/CPU thread. The osnoise specific fields report:
- The RUNTIME IN USE reports the amount of time in microseconds that
the osnoise thread kept looping reading the time.
- The NOISE IN US reports the sum of noise in microseconds observed
by the osnoise tracer during the associated runtime.
- The % OF CPU AVAILABLE reports the percentage of CPU available for
the osnoise thread during the runtime window.
- The MAX SINGLE NOISE IN US reports the maximum single noise observed
during the runtime window.
- The Interference counters display how many each of the respective
interference happened during the runtime window.
Note that the example above shows a high number of HW noise samples.
The reason being is that this sample was taken on a virtual machine,
and the host interference is detected as a hardware interference.
Tracer options
The tracer has a set of options inside the osnoise directory, they are:
- osnoise/cpus: CPUs at which a osnoise thread will execute.
- osnoise/period_us: the period of the osnoise thread.
- osnoise/runtime_us: how long an osnoise thread will look for noise.
- osnoise/stop_tracing_us: stop the system tracing if a single noise
higher than the configured value happens. Writing 0 disables this
option.
- osnoise/stop_tracing_total_us: stop the system tracing if total noise
higher than the configured value happens. Writing 0 disables this
option.
- tracing_threshold: the minimum delta between two time() reads to be
considered as noise, in us. When set to 0, the default value will
be used, which is currently 5 us.
Additional Tracing
In addition to the tracer, a set of tracepoints were added to
facilitate the identification of the osnoise source.
- osnoise:sample_threshold: printed anytime a noise is higher than
the configurable tolerance_ns.
- osnoise:nmi_noise: noise from NMI, including the duration.
- osnoise:irq_noise: noise from an IRQ, including the duration.
- osnoise:softirq_noise: noise from a SoftIRQ, including the
duration.
- osnoise:thread_noise: noise from a thread, including the duration.
Note that all the values are *net values*. For example, if while osnoise
is running, another thread preempts the osnoise thread, it will start a
thread_noise duration at the start. Then, an IRQ takes place, preempting
the thread_noise, starting a irq_noise. When the IRQ ends its execution,
it will compute its duration, and this duration will be subtracted from
the thread_noise, in such a way as to avoid the double accounting of the
IRQ execution. This logic is valid for all sources of noise.
Here is one example of the usage of these tracepoints::
osnoise/8-961 [008] d.h. 5789.857532: irq_noise: local_timer:236 start 5789.857529929 duration 1845 ns
osnoise/8-961 [008] dNh. 5789.858408: irq_noise: local_timer:236 start 5789.858404871 duration 2848 ns
migration/8-54 [008] d... 5789.858413: thread_noise: migration/8:54 start 5789.858409300 duration 3068 ns
osnoise/8-961 [008] .... 5789.858413: sample_threshold: start 5789.858404555 duration 8723 ns interferences 2
In this example, a noise sample of 8 microseconds was reported in the last
line, pointing to two interferences. Looking backward in the trace, the
two previous entries were about the migration thread running after a
timer IRQ execution. The first event is not part of the noise because
it took place one millisecond before.
It is worth noticing that the sum of the duration reported in the
tracepoints is smaller than eight us reported in the sample_threshold.
The reason roots in the overhead of the entry and exit code that happens
before and after any interference execution. This justifies the dual
approach: measuring thread and tracing.
Link: https://lkml.kernel.org/r/e649467042d60e7b62714c9c6751a56299d15119.1624372313.git.bristot@redhat.com
Cc: Phil Auld <pauld@redhat.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Kate Carcia <kcarcia@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Alexandre Chartre <alexandre.chartre@oracle.com>
Cc: Clark Willaims <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
[
Made the following functions static:
trace_irqentry_callback()
trace_irqexit_callback()
trace_intel_irqentry_callback()
trace_intel_irqexit_callback()
Added to include/trace.h:
osnoise_arch_register()
osnoise_arch_unregister()
Fixed define logic for LATENCY_FS_NOTIFY
Reported-by: kernel test robot <lkp@intel.com>
]
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
|
||
|
Steven Rostedt (VMware)
|
6880c987e4 |
tracing: Add LATENCY_FS_NOTIFY to define if latency_fsnotify() is defined
With the coming addition of the osnoise tracer, the configs needed to include the latency_fsnotify() has become more complex, and to keep the declaration in the header file the same as in the C file, just have the logic needed to define it in one place, and that defines LATENCY_FS_NOTIFY which will be used in the C code. Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> |
||
|
Daniel Bristot de Oliveira
|
aa892f8c88 |
trace/hwlat: Remove printk from sampling loop
hwlat has some time operation checks on the sample loop, and it is currently using pr_err (printk) to report them. The problem is that this can lead the system to an unresponsible state due to an overflow of printk messages. This problem can be mitigated by writing the error message to the trace buffer. Remove the printk messages from the sampling loop, switching the to messages in the trace buffer. No functional change. Link: https://lkml.kernel.org/r/9d77c34869748aa105e965c769d24642914eea3a.1624372313.git.bristot@redhat.com Cc: Phil Auld <pauld@redhat.com> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Kate Carcia <kcarcia@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Alexandre Chartre <alexandre.chartre@oracle.com> Cc: Clark Willaims <williams@redhat.com> Cc: John Kacur <jkacur@redhat.com> Cc: Juri Lelli <juri.lelli@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Cc: linux-doc@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> |
||
|
Daniel Bristot de Oliveira
|
f27a1c9e1b |
trace/hwlat: Use trace_min_max_param for width and window params
Use the trace_min_max_param to reduce code duplication. No functional change. Link: https://lkml.kernel.org/r/b91accd5a7c6c14ea02d3379aae974ba22b47dd6.1624372313.git.bristot@redhat.com Cc: Phil Auld <pauld@redhat.com> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Kate Carcia <kcarcia@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Alexandre Chartre <alexandre.chartre@oracle.com> Cc: Clark Willaims <williams@redhat.com> Cc: John Kacur <jkacur@redhat.com> Cc: Juri Lelli <juri.lelli@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Cc: linux-doc@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> |
||
|
Daniel Bristot de Oliveira
|
bc87cf0a08 |
trace: Add a generic function to read/write u64 values from tracefs
The hwlat detector and (in preparation for) the osnoise/timerlat tracers
have a set of u64 parameters that the user can read/write via tracefs.
For instance, we have hwlat_detector's window and width.
To reduce the code duplication, hwlat's window and width share the same
read function. However, they do not share the write functions because
they do different parameter checks. For instance, the width needs to
be smaller than the window, while the window needs to be larger
than the window. The same pattern repeats on osnoise/timerlat, and
a large portion of the code was devoted to the write function.
Despite having different checks, the write functions have the same
structure:
read a user-space buffer
take the lock that protects the value
check for minimum and maximum acceptable values
save the value
release the lock
return success or error
To reduce the code duplication also in the write functions, this patch
provides a generic read and write implementation for u64 values that
need to be within some minimum and/or maximum parameters, while
(potentially) being protected by a lock.
To use this interface, the structure trace_min_max_param needs to be
filled:
struct trace_min_max_param {
struct mutex *lock;
u64 *val;
u64 *min;
u64 *max;
};
The desired value is stored on the variable pointed by *val. If *min
points to a minimum acceptable value, it will be checked during the
write operation. Likewise, if *max points to a maximum allowable value,
it will be checked during the write operation. Finally, if *lock points
to a mutex, it will be taken at the beginning of the operation and
released at the end.
The definition of a trace_min_max_param needs to passed as the
(private) *data for tracefs_create_file(), and the trace_min_max_fops
(added by this patch) as the *fops file_operations.
Link: https://lkml.kernel.org/r/3e35760a7c8b5c55f16ae5ad5fc54a0e71cbe647.1624372313.git.bristot@redhat.com
Cc: Phil Auld <pauld@redhat.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Kate Carcia <kcarcia@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Alexandre Chartre <alexandre.chartre@oracle.com>
Cc: Clark Willaims <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
|
||
|
Daniel Bristot de Oliveira
|
f46b16520a |
trace/hwlat: Implement the per-cpu mode
Implements the per-cpu mode in which a sampling thread is created for each cpu in the "cpus" (and tracing_mask). The per-cpu mode has the potention to speed up the hwlat detection by running on multiple CPUs at the same time, at the cost of higher cpu usage with irqs disabled. Use with care. [ Changed get_cpu_data() to static. Reported-by: kernel test robot <lkp@intel.com> ] Link: https://lkml.kernel.org/r/ec06d0ab340e8460d293772faba19ad8a5c371aa.1624372313.git.bristot@redhat.com Cc: Phil Auld <pauld@redhat.com> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Kate Carcia <kcarcia@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Alexandre Chartre <alexandre.chartre@oracle.com> Cc: Clark Willaims <williams@redhat.com> Cc: John Kacur <jkacur@redhat.com> Cc: Juri Lelli <juri.lelli@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Cc: linux-doc@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> |
||
|
Hugh Dickins
|
fe19bd3dae |
mm, futex: fix shared futex pgoff on shmem huge page
If more than one futex is placed on a shmem huge page, it can happen that waking the second wakes the first instead, and leaves the second waiting: the key's shared.pgoff is wrong. When 3.11 commit |
||
|
Petr Mladek
|
5fa54346ca |
kthread: prevent deadlock when kthread_mod_delayed_work() races with kthread_cancel_delayed_work_sync()
The system might hang with the following backtrace:
schedule+0x80/0x100
schedule_timeout+0x48/0x138
wait_for_common+0xa4/0x134
wait_for_completion+0x1c/0x2c
kthread_flush_work+0x114/0x1cc
kthread_cancel_work_sync.llvm.16514401384283632983+0xe8/0x144
kthread_cancel_delayed_work_sync+0x18/0x2c
xxxx_pm_notify+0xb0/0xd8
blocking_notifier_call_chain_robust+0x80/0x194
pm_notifier_call_chain_robust+0x28/0x4c
suspend_prepare+0x40/0x260
enter_state+0x80/0x3f4
pm_suspend+0x60/0xdc
state_store+0x108/0x144
kobj_attr_store+0x38/0x88
sysfs_kf_write+0x64/0xc0
kernfs_fop_write_iter+0x108/0x1d0
vfs_write+0x2f4/0x368
ksys_write+0x7c/0xec
It is caused by the following race between kthread_mod_delayed_work()
and kthread_cancel_delayed_work_sync():
CPU0 CPU1
Context: Thread A Context: Thread B
kthread_mod_delayed_work()
spin_lock()
__kthread_cancel_work()
spin_unlock()
del_timer_sync()
kthread_cancel_delayed_work_sync()
spin_lock()
__kthread_cancel_work()
spin_unlock()
del_timer_sync()
spin_lock()
work->canceling++
spin_unlock
spin_lock()
queue_delayed_work()
// dwork is put into the worker->delayed_work_list
spin_unlock()
kthread_flush_work()
// flush_work is put at the tail of the dwork
wait_for_completion()
Context: IRQ
kthread_delayed_work_timer_fn()
spin_lock()
list_del_init(&work->node);
spin_unlock()
BANG: flush_work is not longer linked and will never get proceed.
The problem is that kthread_mod_delayed_work() checks work->canceling
flag before canceling the timer.
A simple solution is to (re)check work->canceling after
__kthread_cancel_work(). But then it is not clear what should be
returned when __kthread_cancel_work() removed the work from the queue
(list) and it can't queue it again with the new @delay.
The return value might be used for reference counting. The caller has
to know whether a new work has been queued or an existing one was
replaced.
The proper solution is that kthread_mod_delayed_work() will remove the
work from the queue (list) _only_ when work->canceling is not set. The
flag must be checked after the timer is stopped and the remaining
operations can be done under worker->lock.
Note that kthread_mod_delayed_work() could remove the timer and then
bail out. It is fine. The other canceling caller needs to cancel the
timer as well. The important thing is that the queue (list)
manipulation is done atomically under worker->lock.
Link: https://lkml.kernel.org/r/20210610133051.15337-3-pmladek@suse.com
Fixes:
|
||
|
Petr Mladek
|
34b3d53447 |
kthread_worker: split code for canceling the delayed work timer
Patch series "kthread_worker: Fix race between kthread_mod_delayed_work() and kthread_cancel_delayed_work_sync()". This patchset fixes the race between kthread_mod_delayed_work() and kthread_cancel_delayed_work_sync() including proper return value handling. This patch (of 2): Simple code refactoring as a preparation step for fixing a race between kthread_mod_delayed_work() and kthread_cancel_delayed_work_sync(). It does not modify the existing behavior. Link: https://lkml.kernel.org/r/20210610133051.15337-2-pmladek@suse.com Signed-off-by: Petr Mladek <pmladek@suse.com> Cc: <jenhaochen@google.com> Cc: Martin Liu <liumartin@google.com> Cc: Minchan Kim <minchan@google.com> Cc: Nathan Chancellor <nathan@kernel.org> Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Tejun Heo <tj@kernel.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
||
|
Daniel Bristot de Oliveira
|
7bb7d802af |
trace/hwlat: Switch disable_migrate to mode none
When in the round-robin mode, if the tracer detects a change in the hwlatd thread affinity by an external tool, e.g., taskset, the round-robin logic is disabled. The disable_migrate variable currently tracks this. With the addition of the "mode" config and the mode "none," the disable_migrate logic is equivalent to switch to the "none" mode. Hence, instead of using a hidden variable to track this behavior, switch the mode to none, informing the user about this change. Link: https://lkml.kernel.org/r/a679af672458d6b1f62252605905c5214030f247.1624372313.git.bristot@redhat.com Cc: Phil Auld <pauld@redhat.com> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Kate Carcia <kcarcia@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Alexandre Chartre <alexandre.chartre@oracle.com> Cc: Clark Willaims <williams@redhat.com> Cc: John Kacur <jkacur@redhat.com> Cc: Juri Lelli <juri.lelli@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Cc: linux-doc@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> |
||
|
Daniel Bristot de Oliveira
|
8fa826b734 |
trace/hwlat: Implement the mode config option
Provides the "mode" config to the hardware latency detector. hwlatd has two different operation modes. The default mode is the "round-robin" one, in which a single hwlatd thread runs, migrating among the allowed CPUs in a "round-robin" fashion. This is the current behavior. The "none" sets the allowed cpumask for a single hwlatd thread at the startup, but skips the round-robin, letting the scheduler handle the migration. In preparation to the per-cpu mode. Link: https://lkml.kernel.org/r/f3b1271262aa030c680e26615c1b9b2d71e55e92.1624372313.git.bristot@redhat.com Cc: Phil Auld <pauld@redhat.com> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Kate Carcia <kcarcia@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Alexandre Chartre <alexandre.chartre@oracle.com> Cc: Clark Willaims <williams@redhat.com> Cc: John Kacur <jkacur@redhat.com> Cc: Juri Lelli <juri.lelli@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Cc: linux-doc@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> |
||
|
Daniel Bristot de Oliveira
|
bb1b24cf41 |
trace/hwlat: Fix Clark's email
Clark's email is williams@redhat.com. No functional change. Link: https://lkml.kernel.org/r/6fa4b49e17ab8a1ff19c335ab7cde38d8afb0e29.1624372313.git.bristot@redhat.com Cc: Phil Auld <pauld@redhat.com> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Kate Carcia <kcarcia@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Alexandre Chartre <alexandre.chartre@oracle.com> Cc: Clark Willaims <williams@redhat.com> Cc: John Kacur <jkacur@redhat.com> Cc: Juri Lelli <juri.lelli@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Cc: linux-doc@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> |
||
|
Toke Høiland-Jørgensen
|
782347b6bc |
xdp: Add proper __rcu annotations to redirect map entries
XDP_REDIRECT works by a three-step process: the bpf_redirect() and bpf_redirect_map() helpers will lookup the target of the redirect and store it (along with some other metadata) in a per-CPU struct bpf_redirect_info. Next, when the program returns the XDP_REDIRECT return code, the driver will call xdp_do_redirect() which will use the information thus stored to actually enqueue the frame into a bulk queue structure (that differs slightly by map type, but shares the same principle). Finally, before exiting its NAPI poll loop, the driver will call xdp_do_flush(), which will flush all the different bulk queues, thus completing the redirect. Pointers to the map entries will be kept around for this whole sequence of steps, protected by RCU. However, there is no top-level rcu_read_lock() in the core code; instead drivers add their own rcu_read_lock() around the XDP portions of the code, but somewhat inconsistently as Martin discovered[0]. However, things still work because everything happens inside a single NAPI poll sequence, which means it's between a pair of calls to local_bh_disable()/local_bh_enable(). So Paul suggested[1] that we could document this intention by using rcu_dereference_check() with rcu_read_lock_bh_held() as a second parameter, thus allowing sparse and lockdep to verify that everything is done correctly. This patch does just that: we add an __rcu annotation to the map entry pointers and remove the various comments explaining the NAPI poll assurance strewn through devmap.c in favour of a longer explanation in filter.c. The goal is to have one coherent documentation of the entire flow, and rely on the RCU annotations as a "standard" way of communicating the flow in the map code (which can additionally be understood by sparse and lockdep). The RCU annotation replacements result in a fairly straight-forward replacement where READ_ONCE() becomes rcu_dereference_check(), WRITE_ONCE() becomes rcu_assign_pointer() and xchg() and cmpxchg() gets wrapped in the proper constructs to cast the pointer back and forth between __rcu and __kernel address space (for the benefit of sparse). The one complication is that xskmap has a few constructions where double-pointers are passed back and forth; these simply all gain __rcu annotations, and only the final reference/dereference to the inner-most pointer gets changed. With this, everything can be run through sparse without eliciting complaints, and lockdep can verify correctness even without the use of rcu_read_lock() in the drivers. Subsequent patches will clean these up from the drivers. [0] https://lore.kernel.org/bpf/20210415173551.7ma4slcbqeyiba2r@kafai-mbp.dhcp.thefacebook.com/ [1] https://lore.kernel.org/bpf/20210419165837.GA975577@paulmck-ThinkPad-P17-Gen-1/ Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20210624160609.292325-6-toke@redhat.com |
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Toke Høiland-Jørgensen
|
694cea395f |
bpf: Allow RCU-protected lookups to happen from bh context
XDP programs are called from a NAPI poll context, which means the RCU reference liveness is ensured by local_bh_disable(). Add rcu_read_lock_bh_held() as a condition to the RCU checks for map lookups so lockdep understands that the dereferences are safe from inside *either* an rcu_read_lock() section *or* a local_bh_disable() section. While both bh_disabled and rcu_read_lock() provide RCU protection, they are semantically distinct, so we need both conditions to prevent lockdep complaints. This change is done in preparation for removing the redundant rcu_read_lock()s from drivers. Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Martin KaFai Lau <kafai@fb.com> Link: https://lore.kernel.org/bpf/20210624160609.292325-5-toke@redhat.com |
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Linus Torvalds
|
7749b0337b |
Merge tag 'core-urgent-2021-06-24' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull sigqueue cache fix from Ingo Molnar: "Fix a memory leak in the recently introduced sigqueue cache" * tag 'core-urgent-2021-06-24' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: signal: Prevent sigqueue caching after task got released |
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Linus Torvalds
|
666751701b |
Merge tag 'sched-urgent-2021-06-24' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fix from Ingo Molnar: "A last minute cgroup bandwidth scheduling fix for a recently introduced logic fail which triggered a kernel warning by LTP's cfs_bandwidth01 test" * tag 'sched-urgent-2021-06-24' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: sched/fair: Ensure that the CFS parent is added after unthrottling |
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Linus Torvalds
|
c0e457851f |
Merge tag 'objtool-urgent-2021-06-24' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull objtool fixes from Ingo Molnar:
"Address a number of objtool warnings that got reported.
No change in behavior intended, but code generation might be impacted
by commit
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Cassio Neri
|
2760105516 |
time: Improve performance of time64_to_tm()
The current implementation of time64_to_tm() contains unnecessary loops, branches and look-up tables. The new one uses an arithmetic-based algorithm appeared in [1] and is approximately 3x faster (YMMV). The drawback is that the new code isn't intuitive and contains many 'magic numbers' (not unusual for this type of algorithm). However, [1] justifies all those numbers and, given this function's history, the code is unlikely to need much maintenance, if any at all. Add a KUnit test for it which checks every day in a 160,000 years interval centered at 1970-01-01 against the expected result. [1] Neri, Schneider, "Euclidean Affine Functions and Applications to Calendar Algorithms". https://arxiv.org/abs/2102.06959 Signed-off-by: Cassio Neri <cassio.neri@gmail.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20210622213616.313046-1-cassio.neri@gmail.com |
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Beata Michalska
|
c744dc4ab5 |
sched/topology: Rework CPU capacity asymmetry detection
Currently the CPU capacity asymmetry detection, performed through asym_cpu_capacity_level, tries to identify the lowest topology level at which the highest CPU capacity is being observed, not necessarily finding the level at which all possible capacity values are visible to all CPUs, which might be bit problematic for some possible/valid asymmetric topologies i.e.: DIE [ ] MC [ ][ ] CPU [0] [1] [2] [3] [4] [5] [6] [7] Capacity |.....| |.....| |.....| |.....| L M B B Where: arch_scale_cpu_capacity(L) = 512 arch_scale_cpu_capacity(M) = 871 arch_scale_cpu_capacity(B) = 1024 In this particular case, the asymmetric topology level will point at MC, as all possible CPU masks for that level do cover the CPU with the highest capacity. It will work just fine for the first cluster, not so much for the second one though (consider the find_energy_efficient_cpu which might end up attempting the energy aware wake-up for a domain that does not see any asymmetry at all) Rework the way the capacity asymmetry levels are being detected, allowing to point to the lowest topology level (for a given CPU), where full set of available CPU capacities is visible to all CPUs within given domain. As a result, the per-cpu sd_asym_cpucapacity might differ across the domains. This will have an impact on EAS wake-up placement in a way that it might see different range of CPUs to be considered, depending on the given current and target CPUs. Additionally, those levels, where any range of asymmetry (not necessarily full) is being detected will get identified as well. The selected asymmetric topology level will be denoted by SD_ASYM_CPUCAPACITY_FULL sched domain flag whereas the 'sub-levels' would receive the already used SD_ASYM_CPUCAPACITY flag. This allows maintaining the current behaviour for asymmetric topologies, with misfit migration operating correctly on lower levels, if applicable, as any asymmetry is enough to trigger the misfit migration. The logic there relies on the SD_ASYM_CPUCAPACITY flag and does not relate to the full asymmetry level denoted by the sd_asym_cpucapacity pointer. Detecting the CPU capacity asymmetry is being based on a set of available CPU capacities for all possible CPUs. This data is being generated upon init and updated once CPU topology changes are being detected (through arch_update_cpu_topology). As such, any changes to identified CPU capacities (like initializing cpufreq) need to be explicitly advertised by corresponding archs to trigger rebuilding the data. Additional -dflags- parameter, used when building sched domains, has been removed as well, as the asymmetry flags are now being set directly in sd_init. Suggested-by: Peter Zijlstra <peterz@infradead.org> Suggested-by: Valentin Schneider <valentin.schneider@arm.com> Signed-off-by: Beata Michalska <beata.michalska@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Tested-by: Valentin Schneider <valentin.schneider@arm.com> Link: https://lore.kernel.org/r/20210603140627.8409-3-beata.michalska@arm.com |
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Zhaoyang Huang
|
8f91efd870 |
psi: Fix race between psi_trigger_create/destroy
Race detected between psi_trigger_destroy/create as shown below, which
cause panic by accessing invalid psi_system->poll_wait->wait_queue_entry
and psi_system->poll_timer->entry->next. Under this modification, the
race window is removed by initialising poll_wait and poll_timer in
group_init which are executed only once at beginning.
psi_trigger_destroy() psi_trigger_create()
mutex_lock(trigger_lock);
rcu_assign_pointer(poll_task, NULL);
mutex_unlock(trigger_lock);
mutex_lock(trigger_lock);
if (!rcu_access_pointer(group->poll_task)) {
timer_setup(poll_timer, poll_timer_fn, 0);
rcu_assign_pointer(poll_task, task);
}
mutex_unlock(trigger_lock);
synchronize_rcu();
del_timer_sync(poll_timer); <-- poll_timer has been reinitialized by
psi_trigger_create()
So, trigger_lock/RCU correctly protects destruction of
group->poll_task but misses this race affecting poll_timer and
poll_wait.
Fixes:
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Huaixin Chang
|
f4183717b3 |
sched/fair: Introduce the burstable CFS controller
The CFS bandwidth controller limits CPU requests of a task group to
quota during each period. However, parallel workloads might be bursty
so that they get throttled even when their average utilization is under
quota. And they are latency sensitive at the same time so that
throttling them is undesired.
We borrow time now against our future underrun, at the cost of increased
interference against the other system users. All nicely bounded.
Traditional (UP-EDF) bandwidth control is something like:
(U = \Sum u_i) <= 1
This guaranteeds both that every deadline is met and that the system is
stable. After all, if U were > 1, then for every second of walltime,
we'd have to run more than a second of program time, and obviously miss
our deadline, but the next deadline will be further out still, there is
never time to catch up, unbounded fail.
This work observes that a workload doesn't always executes the full
quota; this enables one to describe u_i as a statistical distribution.
For example, have u_i = {x,e}_i, where x is the p(95) and x+e p(100)
(the traditional WCET). This effectively allows u to be smaller,
increasing the efficiency (we can pack more tasks in the system), but at
the cost of missing deadlines when all the odds line up. However, it
does maintain stability, since every overrun must be paired with an
underrun as long as our x is above the average.
That is, suppose we have 2 tasks, both specify a p(95) value, then we
have a p(95)*p(95) = 90.25% chance both tasks are within their quota and
everything is good. At the same time we have a p(5)p(5) = 0.25% chance
both tasks will exceed their quota at the same time (guaranteed deadline
fail). Somewhere in between there's a threshold where one exceeds and
the other doesn't underrun enough to compensate; this depends on the
specific CDFs.
At the same time, we can say that the worst case deadline miss, will be
\Sum e_i; that is, there is a bounded tardiness (under the assumption
that x+e is indeed WCET).
The benefit of burst is seen when testing with schbench. Default value of
kernel.sched_cfs_bandwidth_slice_us(5ms) and CONFIG_HZ(1000) is used.
mkdir /sys/fs/cgroup/cpu/test
echo $$ > /sys/fs/cgroup/cpu/test/cgroup.procs
echo 100000 > /sys/fs/cgroup/cpu/test/cpu.cfs_quota_us
echo 100000 > /sys/fs/cgroup/cpu/test/cpu.cfs_burst_us
./schbench -m 1 -t 3 -r 20 -c 80000 -R 10
The average CPU usage is at 80%. I run this for 10 times, and got long tail
latency for 6 times and got throttled for 8 times.
Tail latencies are shown below, and it wasn't the worst case.
Latency percentiles (usec)
50.0000th: 19872
75.0000th: 21344
90.0000th: 22176
95.0000th: 22496
*99.0000th: 22752
99.5000th: 22752
99.9000th: 22752
min=0, max=22727
rps: 9.90 p95 (usec) 22496 p99 (usec) 22752 p95/cputime 28.12% p99/cputime 28.44%
The interferenece when using burst is valued by the possibilities for
missing the deadline and the average WCET. Test results showed that when
there many cgroups or CPU is under utilized, the interference is
limited. More details are shown in:
https://lore.kernel.org/lkml/5371BD36-55AE-4F71-B9D7-B86DC32E3D2B@linux.alibaba.com/
Co-developed-by: Shanpei Chen <shanpeic@linux.alibaba.com>
Signed-off-by: Shanpei Chen <shanpeic@linux.alibaba.com>
Co-developed-by: Tianchen Ding <dtcccc@linux.alibaba.com>
Signed-off-by: Tianchen Ding <dtcccc@linux.alibaba.com>
Signed-off-by: Huaixin Chang <changhuaixin@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ben Segall <bsegall@google.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20210621092800.23714-2-changhuaixin@linux.alibaba.com
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David Gow
|
388ca2e024 |
kernel/sysctl-test: Remove some casts which are no-longer required
With some of the stricter type checking in KUnit's EXPECT macros removed, several casts in sysctl-test are no longer required. Remove the unnecessary casts, making the conditions clearer. Signed-off-by: David Gow <davidgow@google.com> Reviewed-by: Brendan Higgins <brendanhiggins@google.com> Signed-off-by: Shuah Khan <skhan@linuxfoundation.org> |
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David S. Miller
|
c2f5c57d99 |
Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf
Daniel Borkmann says: ==================== pull-request: bpf 2021-06-23 The following pull-request contains BPF updates for your *net* tree. We've added 14 non-merge commits during the last 6 day(s) which contain a total of 13 files changed, 137 insertions(+), 64 deletions(-). Note that when you merge net into net-next, there is a small merge conflict between |
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Peter Zijlstra
|
012669c740 |
perf: Fix task context PMU for Hetero
On HETEROGENEOUS hardware (ARM big.Little, Intel Alderlake etc.) each
CPU might have a different hardware PMU. Since each such PMU is
represented by a different struct pmu, but we only have a single HW
task context.
That means that the task context needs to switch PMU type when it
switches CPUs.
Not doing this means that ctx->pmu calls (pmu_{dis,en}able(),
{start,commit,cancel}_txn() etc.) are called against the wrong PMU and
things will go wobbly.
Fixes:
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Linus Torvalds
|
8fd2ed1c01 |
Merge branch 'stable/for-linus-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/swiotlb
Pull swiotlb fix from Konrad Rzeszutek Wilk: "A fix for the regression for the DMA operations where the offset was ignored and corruptions would appear. Going forward there will be a cleanups to make the offset and alignment logic more clearer and better test-cases to help with this" * 'stable/for-linus-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/swiotlb: swiotlb: manipulate orig_addr when tlb_addr has offset |
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Mark Brown
|
7fb593cbd8 | Merge remote-tracking branch 'regulator/for-5.14' into regulator-next | ||
|
John Fastabend
|
7506d211b9 |
bpf: Fix null ptr deref with mixed tail calls and subprogs
The sub-programs prog->aux->poke_tab[] is populated in jit_subprogs() and
then used when emitting 'BPF_JMP|BPF_TAIL_CALL' insn->code from the
individual JITs. The poke_tab[] to use is stored in the insn->imm by
the code adding it to that array slot. The JIT then uses imm to find the
right entry for an individual instruction. In the x86 bpf_jit_comp.c
this is done by calling emit_bpf_tail_call_direct with the poke_tab[]
of the imm value.
However, we observed the below null-ptr-deref when mixing tail call
programs with subprog programs. For this to happen we just need to
mix bpf-2-bpf calls and tailcalls with some extra calls or instructions
that would be patched later by one of the fixup routines. So whats
happening?
Before the fixup_call_args() -- where the jit op is done -- various
code patching is done by do_misc_fixups(). This may increase the
insn count, for example when we patch map_lookup_up using map_gen_lookup
hook. This does two things. First, it means the instruction index,
insn_idx field, of a tail call instruction will move by a 'delta'.
In verifier code,
struct bpf_jit_poke_descriptor desc = {
.reason = BPF_POKE_REASON_TAIL_CALL,
.tail_call.map = BPF_MAP_PTR(aux->map_ptr_state),
.tail_call.key = bpf_map_key_immediate(aux),
.insn_idx = i + delta,
};
Then subprog start values subprog_info[i].start will be updated
with the delta and any poke descriptor index will also be updated
with the delta in adjust_poke_desc(). If we look at the adjust
subprog starts though we see its only adjusted when the delta
occurs before the new instructions,
/* NOTE: fake 'exit' subprog should be updated as well. */
for (i = 0; i <= env->subprog_cnt; i++) {
if (env->subprog_info[i].start <= off)
continue;
Earlier subprograms are not changed because their start values
are not moved. But, adjust_poke_desc() does the offset + delta
indiscriminately. The result is poke descriptors are potentially
corrupted.
Then in jit_subprogs() we only populate the poke_tab[]
when the above insn_idx is less than the next subprogram start. From
above we corrupted our insn_idx so we might incorrectly assume a
poke descriptor is not used in a subprogram omitting it from the
subprogram. And finally when the jit runs it does the deref of poke_tab
when emitting the instruction and crashes with below. Because earlier
step omitted the poke descriptor.
The fix is straight forward with above context. Simply move same logic
from adjust_subprog_starts() into adjust_poke_descs() and only adjust
insn_idx when needed.
[ 82.396354] bpf_testmod: version magic '5.12.0-rc2alu+ SMP preempt mod_unload ' should be '5.12.0+ SMP preempt mod_unload '
[ 82.623001] loop10: detected capacity change from 0 to 8
[ 88.487424] ==================================================================
[ 88.487438] BUG: KASAN: null-ptr-deref in do_jit+0x184a/0x3290
[ 88.487455] Write of size 8 at addr 0000000000000008 by task test_progs/5295
[ 88.487471] CPU: 7 PID: 5295 Comm: test_progs Tainted: G I 5.12.0+ #386
[ 88.487483] Hardware name: Dell Inc. Precision 5820 Tower/002KVM, BIOS 1.9.2 01/24/2019
[ 88.487490] Call Trace:
[ 88.487498] dump_stack+0x93/0xc2
[ 88.487515] kasan_report.cold+0x5f/0xd8
[ 88.487530] ? do_jit+0x184a/0x3290
[ 88.487542] do_jit+0x184a/0x3290
...
[ 88.487709] bpf_int_jit_compile+0x248/0x810
...
[ 88.487765] bpf_check+0x3718/0x5140
...
[ 88.487920] bpf_prog_load+0xa22/0xf10
Fixes:
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Mimi Zohar
|
0c18f29aae |
module: limit enabling module.sig_enforce
Irrespective as to whether CONFIG_MODULE_SIG is configured, specifying
"module.sig_enforce=1" on the boot command line sets "sig_enforce".
Only allow "sig_enforce" to be set when CONFIG_MODULE_SIG is configured.
This patch makes the presence of /sys/module/module/parameters/sig_enforce
dependent on CONFIG_MODULE_SIG=y.
Fixes:
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|
Nick Desaulniers
|
51c2ee6d12 |
Kconfig: Introduce ARCH_WANTS_NO_INSTR and CC_HAS_NO_PROFILE_FN_ATTR
We don't want compiler instrumentation to touch noinstr functions, which are annotated with the no_profile_instrument_function function attribute. Add a Kconfig test for this and make GCOV depend on it, and in the future, PGO. If an architecture is using noinstr, it should denote that via this Kconfig value. That makes Kconfigs that depend on noinstr able to express dependencies in an architecturally agnostic way. Cc: Masahiro Yamada <masahiroy@kernel.org> Link: https://lore.kernel.org/lkml/YMTn9yjuemKFLbws@hirez.programming.kicks-ass.net/ Link: https://lore.kernel.org/lkml/YMcssV%2Fn5IBGv4f0@hirez.programming.kicks-ass.net/ Suggested-by: Nathan Chancellor <nathan@kernel.org> Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Acked-by: Mark Rutland <mark.rutland@arm.com> Acked-by: Heiko Carstens <hca@linux.ibm.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20210621231822.2848305-4-ndesaulniers@google.com |
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|
Bui Quang Minh
|
7dd5d437c2 |
bpf: Fix integer overflow in argument calculation for bpf_map_area_alloc
In 32-bit architecture, the result of sizeof() is a 32-bit integer so the expression becomes the multiplication between 2 32-bit integer which can potentially leads to integer overflow. As a result, bpf_map_area_alloc() allocates less memory than needed. Fix this by casting 1 operand to u64. Fixes: |
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Baokun Li
|
4e82d2e20f |
clockevents: Use list_move() instead of list_del()/list_add()
Simplify the code. Reported-by: Hulk Robot <hulkci@huawei.com> Signed-off-by: Baokun Li <libaokun1@huawei.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20210609070242.1322450-1-libaokun1@huawei.com |
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Feng Tang
|
22a2238337 |
clocksource: Print deviation in nanoseconds when a clocksource becomes unstable
Currently when an unstable clocksource is detected, the raw counters of that clocksource and watchdog will be printed, which can only be understood after some math calculation. So print the delta in nanoseconds as well to make it easier for humans to check the results. [ paulmck: Fix typo. ] Signed-off-by: Feng Tang <feng.tang@intel.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20210527190124.440372-6-paulmck@kernel.org |
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Paul E. McKenney
|
1253b9b87e |
clocksource: Provide kernel module to test clocksource watchdog
When the clocksource watchdog marks a clock as unstable, this might be due to that clock being unstable or it might be due to delays that happen to occur between the reads of the two clocks. It would be good to have a way of testing the clocksource watchdog's ability to distinguish between these two causes of clock skew and instability. Therefore, provide a new clocksource-wdtest module selected by a new TEST_CLOCKSOURCE_WATCHDOG Kconfig option. This module has a single module parameter named "holdoff" that provides the number of seconds of delay before testing should start, which defaults to zero when built as a module and to 10 seconds when built directly into the kernel. Very large systems that boot slowly may need to increase the value of this module parameter. This module uses hand-crafted clocksource structures to do its testing, thus avoiding messing up timing for the rest of the kernel and for user applications. This module first verifies that the ->uncertainty_margin field of the clocksource structures are set sanely. It then tests the delay-detection capability of the clocksource watchdog, increasing the number of consecutive delays injected, first provoking console messages complaining about the delays and finally forcing a clock-skew event. Unexpected test results cause at least one WARN_ON_ONCE() console splat. If there are no splats, the test has passed. Finally, it fuzzes the value returned from a clocksource to test the clocksource watchdog's ability to detect time skew. This module checks the state of its clocksource after each test, and uses WARN_ON_ONCE() to emit a console splat if there are any failures. This should enable all types of test frameworks to detect any such failures. This facility is intended for diagnostic use only, and should be avoided on production systems. Reported-by: Chris Mason <clm@fb.com> Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Feng Tang <feng.tang@intel.com> Link: https://lore.kernel.org/r/20210527190124.440372-5-paulmck@kernel.org |