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Merge tag 'locking-core-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Browse Source 
Pull locking updates from Thomas Gleixner:
 "A moderate set of locking updates:

   - A few extensions to the rwsem API and support for opportunistic
     spinning and lock stealing

   - lockdep selftest improvements

   - Documentation updates

   - Cleanups and small fixes all over the place"

* tag 'locking-core-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (21 commits)
  seqlock: kernel-doc: Specify when preemption is automatically altered
  seqlock: Prefix internal seqcount_t-only macros with a "do_"
  Documentation: seqlock: s/LOCKTYPE/LOCKNAME/g
  locking/rwsem: Remove reader optimistic spinning
  locking/rwsem: Enable reader optimistic lock stealing
  locking/rwsem: Prevent potential lock starvation
  locking/rwsem: Pass the current atomic count to rwsem_down_read_slowpath()
  locking/rwsem: Fold __down_{read,write}*()
  locking/rwsem: Introduce rwsem_write_trylock()
  locking/rwsem: Better collate rwsem_read_trylock()
  rwsem: Implement down_read_interruptible
  rwsem: Implement down_read_killable_nested
  refcount: Fix a kernel-doc markup
  completion: Drop init_completion define
  atomic: Update MAINTAINERS
  atomic: Delete obsolete documentation
  seqlock: Rename __seqprop() users
  lockdep/selftest: Add spin_nest_lock test
  lockdep/selftests: Fix PROVE_RAW_LOCK_NESTING
  seqlock: avoid -Wshadow warnings
  ...
This commit is contained in:
Linus Torvalds
2020-12-14 17:27:47 -08:00
parent 8c1dccc803 cb262935a1
commit e857b6fcc5
11 changed files with 254 additions and 1008 deletions
Download Patch File Download Diff File Expand all files Collapse all files
kernel/futex.c
-2
View File
@@ -310,8 +310,6 @@ static inline bool should_fail_futex(bool fshared)
#ifdef CONFIG_COMPAT
static void compat_exit_robust_list(struct task_struct *curr);
#else
static inline void compat_exit_robust_list(struct task_struct *curr) { }
#endif
/*
kernel/locking/lock_events_list.h
+2 -4
View File
@@ -56,13 +56,11 @@ LOCK_EVENT(rwsem_sleep_reader) /* # of reader sleeps */
LOCK_EVENT(rwsem_sleep_writer) /* # of writer sleeps */
LOCK_EVENT(rwsem_wake_reader) /* # of reader wakeups */
LOCK_EVENT(rwsem_wake_writer) /* # of writer wakeups */
LOCK_EVENT(rwsem_opt_rlock) /* # of opt-acquired read locks */
LOCK_EVENT(rwsem_opt_wlock) /* # of opt-acquired write locks */
LOCK_EVENT(rwsem_opt_lock) /* # of opt-acquired write locks */
LOCK_EVENT(rwsem_opt_fail) /* # of failed optspins */
LOCK_EVENT(rwsem_opt_nospin) /* # of disabled optspins */
LOCK_EVENT(rwsem_opt_norspin) /* # of disabled reader-only optspins */
LOCK_EVENT(rwsem_opt_rlock2) /* # of opt-acquired 2ndary read locks */
LOCK_EVENT(rwsem_rlock) /* # of read locks acquired */
LOCK_EVENT(rwsem_rlock_steal) /* # of read locks by lock stealing */
LOCK_EVENT(rwsem_rlock_fast) /* # of fast read locks acquired */
LOCK_EVENT(rwsem_rlock_fail) /* # of failed read lock acquisitions */
LOCK_EVENT(rwsem_rlock_handoff) /* # of read lock handoffs */
kernel/locking/rwsem.c
+137 -248
View File
@@ -31,19 +31,13 @@
#include "lock_events.h"
/*
* The least significant 3 bits of the owner value has the following
* The least significant 2 bits of the owner value has the following
* meanings when set.
* - Bit 0: RWSEM_READER_OWNED - The rwsem is owned by readers
* - Bit 1: RWSEM_RD_NONSPINNABLE - Readers cannot spin on this lock.
* - Bit 2: RWSEM_WR_NONSPINNABLE - Writers cannot spin on this lock.
* - Bit 1: RWSEM_NONSPINNABLE - Cannot spin on a reader-owned lock
*
* When the rwsem is either owned by an anonymous writer, or it is
* reader-owned, but a spinning writer has timed out, both nonspinnable
* bits will be set to disable optimistic spinning by readers and writers.
* In the later case, the last unlocking reader should then check the
* writer nonspinnable bit and clear it only to give writers preference
* to acquire the lock via optimistic spinning, but not readers. Similar
* action is also done in the reader slowpath.
* When the rwsem is reader-owned and a spinning writer has timed out,
* the nonspinnable bit will be set to disable optimistic spinning.
* When a writer acquires a rwsem, it puts its task_struct pointer
* into the owner field. It is cleared after an unlock.
@@ -59,46 +53,14 @@
* is involved. Ideally we would like to track all the readers that own
* a rwsem, but the overhead is simply too big.
*
* Reader optimistic spinning is helpful when the reader critical section
* is short and there aren't that many readers around. It makes readers
* relatively more preferred than writers. When a writer times out spinning
* on a reader-owned lock and set the nospinnable bits, there are two main
* reasons for that.
*
* 1) The reader critical section is long, perhaps the task sleeps after
* acquiring the read lock.
* 2) There are just too many readers contending the lock causing it to
* take a while to service all of them.
*
* In the former case, long reader critical section will impede the progress
* of writers which is usually more important for system performance. In
* the later case, reader optimistic spinning tends to make the reader
* groups that contain readers that acquire the lock together smaller
* leading to more of them. That may hurt performance in some cases. In
* other words, the setting of nonspinnable bits indicates that reader
* optimistic spinning may not be helpful for those workloads that cause
* it.
*
* Therefore, any writers that had observed the setting of the writer
* nonspinnable bit for a given rwsem after they fail to acquire the lock
* via optimistic spinning will set the reader nonspinnable bit once they
* acquire the write lock. Similarly, readers that observe the setting
* of reader nonspinnable bit at slowpath entry will set the reader
* nonspinnable bits when they acquire the read lock via the wakeup path.
*
* Once the reader nonspinnable bit is on, it will only be reset when
* a writer is able to acquire the rwsem in the fast path or somehow a
* reader or writer in the slowpath doesn't observe the nonspinable bit.
*
* This is to discourage reader optmistic spinning on that particular
* rwsem and make writers more preferred. This adaptive disabling of reader
* optimistic spinning will alleviate the negative side effect of this
* feature.
* A fast path reader optimistic lock stealing is supported when the rwsem
* is previously owned by a writer and the following conditions are met:
* - OSQ is empty
* - rwsem is not currently writer owned
* - the handoff isn't set.
*/
#define RWSEM_READER_OWNED (1UL << 0)
#define RWSEM_RD_NONSPINNABLE (1UL << 1)
#define RWSEM_WR_NONSPINNABLE (1UL << 2)
#define RWSEM_NONSPINNABLE (RWSEM_RD_NONSPINNABLE | RWSEM_WR_NONSPINNABLE)
#define RWSEM_NONSPINNABLE (1UL << 1)
#define RWSEM_OWNER_FLAGS_MASK (RWSEM_READER_OWNED | RWSEM_NONSPINNABLE)
#ifdef CONFIG_DEBUG_RWSEMS
@@ -203,7 +165,7 @@ static inline void __rwsem_set_reader_owned(struct rw_semaphore *sem,
struct task_struct *owner)
{
unsigned long val = (unsigned long)owner | RWSEM_READER_OWNED |
(atomic_long_read(&sem->owner) & RWSEM_RD_NONSPINNABLE);
(atomic_long_read(&sem->owner) & RWSEM_NONSPINNABLE);
atomic_long_set(&sem->owner, val);
}
@@ -270,12 +232,31 @@ static inline void rwsem_set_nonspinnable(struct rw_semaphore *sem)
owner | RWSEM_NONSPINNABLE));
}
static inline bool rwsem_read_trylock(struct rw_semaphore *sem)
static inline bool rwsem_read_trylock(struct rw_semaphore *sem, long *cntp)
{
long cnt = atomic_long_add_return_acquire(RWSEM_READER_BIAS, &sem->count);
if (WARN_ON_ONCE(cnt < 0))
*cntp = atomic_long_add_return_acquire(RWSEM_READER_BIAS, &sem->count);
if (WARN_ON_ONCE(*cntp < 0))
rwsem_set_nonspinnable(sem);
return !(cnt & RWSEM_READ_FAILED_MASK);
if (!(*cntp & RWSEM_READ_FAILED_MASK)) {
rwsem_set_reader_owned(sem);
return true;
}
return false;
}
static inline bool rwsem_write_trylock(struct rw_semaphore *sem)
{
long tmp = RWSEM_UNLOCKED_VALUE;
if (atomic_long_try_cmpxchg_acquire(&sem->count, &tmp, RWSEM_WRITER_LOCKED)) {
rwsem_set_owner(sem);
return true;
}
return false;
}
/*
@@ -353,7 +334,6 @@ struct rwsem_waiter {
struct task_struct *task;
enum rwsem_waiter_type type;
unsigned long timeout;
unsigned long last_rowner;
};
#define rwsem_first_waiter(sem) \
list_first_entry(&sem->wait_list, struct rwsem_waiter, list)
@@ -467,10 +447,6 @@ static void rwsem_mark_wake(struct rw_semaphore *sem,
* the reader is copied over.
*/
owner = waiter->task;
if (waiter->last_rowner & RWSEM_RD_NONSPINNABLE) {
owner = (void *)((unsigned long)owner | RWSEM_RD_NONSPINNABLE);
lockevent_inc(rwsem_opt_norspin);
}
__rwsem_set_reader_owned(sem, owner);
}
@@ -601,30 +577,6 @@ static inline bool rwsem_try_write_lock(struct rw_semaphore *sem,
}
#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
/*
* Try to acquire read lock before the reader is put on wait queue.
* Lock acquisition isn't allowed if the rwsem is locked or a writer handoff
* is ongoing.
*/
static inline bool rwsem_try_read_lock_unqueued(struct rw_semaphore *sem)
{
long count = atomic_long_read(&sem->count);
if (count & (RWSEM_WRITER_MASK | RWSEM_FLAG_HANDOFF))
return false;
count = atomic_long_fetch_add_acquire(RWSEM_READER_BIAS, &sem->count);
if (!(count & (RWSEM_WRITER_MASK | RWSEM_FLAG_HANDOFF))) {
rwsem_set_reader_owned(sem);
lockevent_inc(rwsem_opt_rlock);
return true;
}
/* Back out the change */
atomic_long_add(-RWSEM_READER_BIAS, &sem->count);
return false;
}
/*
* Try to acquire write lock before the writer has been put on wait queue.
*/
@@ -636,7 +588,7 @@ static inline bool rwsem_try_write_lock_unqueued(struct rw_semaphore *sem)
if (atomic_long_try_cmpxchg_acquire(&sem->count, &count,
count | RWSEM_WRITER_LOCKED)) {
rwsem_set_owner(sem);
lockevent_inc(rwsem_opt_wlock);
lockevent_inc(rwsem_opt_lock);
return true;
}
}
@@ -652,8 +604,7 @@ static inline bool owner_on_cpu(struct task_struct *owner)
return owner->on_cpu && !vcpu_is_preempted(task_cpu(owner));
}
static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem,
unsigned long nonspinnable)
static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)
{
struct task_struct *owner;
unsigned long flags;
@@ -670,7 +621,7 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem,
/*
* Don't check the read-owner as the entry may be stale.
*/
if ((flags & nonspinnable) ||
if ((flags & RWSEM_NONSPINNABLE) ||
(owner && !(flags & RWSEM_READER_OWNED) && !owner_on_cpu(owner)))
ret = false;
rcu_read_unlock();
@@ -700,9 +651,9 @@ enum owner_state {
#define OWNER_SPINNABLE (OWNER_NULL | OWNER_WRITER | OWNER_READER)
static inline enum owner_state
rwsem_owner_state(struct task_struct *owner, unsigned long flags, unsigned long nonspinnable)
rwsem_owner_state(struct task_struct *owner, unsigned long flags)
{
if (flags & nonspinnable)
if (flags & RWSEM_NONSPINNABLE)
return OWNER_NONSPINNABLE;
if (flags & RWSEM_READER_OWNED)
@@ -712,14 +663,14 @@ rwsem_owner_state(struct task_struct *owner, unsigned long flags, unsigned long
}
static noinline enum owner_state
rwsem_spin_on_owner(struct rw_semaphore *sem, unsigned long nonspinnable)
rwsem_spin_on_owner(struct rw_semaphore *sem)
{
struct task_struct *new, *owner;
unsigned long flags, new_flags;
enum owner_state state;
owner = rwsem_owner_flags(sem, &flags);
state = rwsem_owner_state(owner, flags, nonspinnable);
state = rwsem_owner_state(owner, flags);
if (state != OWNER_WRITER)
return state;
@@ -733,7 +684,7 @@ rwsem_spin_on_owner(struct rw_semaphore *sem, unsigned long nonspinnable)
*/
new = rwsem_owner_flags(sem, &new_flags);
if ((new != owner) || (new_flags != flags)) {
state = rwsem_owner_state(new, new_flags, nonspinnable);
state = rwsem_owner_state(new, new_flags);
break;
}
@@ -782,14 +733,12 @@ static inline u64 rwsem_rspin_threshold(struct rw_semaphore *sem)
return sched_clock() + delta;
}
static bool rwsem_optimistic_spin(struct rw_semaphore *sem, bool wlock)
static bool rwsem_optimistic_spin(struct rw_semaphore *sem)
{
bool taken = false;
int prev_owner_state = OWNER_NULL;
int loop = 0;
u64 rspin_threshold = 0;
unsigned long nonspinnable = wlock ? RWSEM_WR_NONSPINNABLE
: RWSEM_RD_NONSPINNABLE;
preempt_disable();
@@ -806,15 +755,14 @@ static bool rwsem_optimistic_spin(struct rw_semaphore *sem, bool wlock)
for (;;) {
enum owner_state owner_state;
owner_state = rwsem_spin_on_owner(sem, nonspinnable);
owner_state = rwsem_spin_on_owner(sem);
if (!(owner_state & OWNER_SPINNABLE))
break;
/*
* Try to acquire the lock
*/
taken = wlock ? rwsem_try_write_lock_unqueued(sem)
: rwsem_try_read_lock_unqueued(sem);
taken = rwsem_try_write_lock_unqueued(sem);
if (taken)
break;
@@ -822,7 +770,7 @@ static bool rwsem_optimistic_spin(struct rw_semaphore *sem, bool wlock)
/*
* Time-based reader-owned rwsem optimistic spinning
*/
if (wlock && (owner_state == OWNER_READER)) {
if (owner_state == OWNER_READER) {
/*
* Re-initialize rspin_threshold every time when
* the owner state changes from non-reader to reader.
@@ -831,7 +779,7 @@ static bool rwsem_optimistic_spin(struct rw_semaphore *sem, bool wlock)
* the beginning of the 2nd reader phase.
*/
if (prev_owner_state != OWNER_READER) {
if (rwsem_test_oflags(sem, nonspinnable))
if (rwsem_test_oflags(sem, RWSEM_NONSPINNABLE))
break;
rspin_threshold = rwsem_rspin_threshold(sem);
loop = 0;
@@ -907,78 +855,30 @@ done:
}
/*
* Clear the owner's RWSEM_WR_NONSPINNABLE bit if it is set. This should
* Clear the owner's RWSEM_NONSPINNABLE bit if it is set. This should
* only be called when the reader count reaches 0.
*
* This give writers better chance to acquire the rwsem first before
* readers when the rwsem was being held by readers for a relatively long
* period of time. Race can happen that an optimistic spinner may have
* just stolen the rwsem and set the owner, but just clearing the
* RWSEM_WR_NONSPINNABLE bit will do no harm anyway.
*/
static inline void clear_wr_nonspinnable(struct rw_semaphore *sem)
static inline void clear_nonspinnable(struct rw_semaphore *sem)
{
if (rwsem_test_oflags(sem, RWSEM_WR_NONSPINNABLE))
atomic_long_andnot(RWSEM_WR_NONSPINNABLE, &sem->owner);
if (rwsem_test_oflags(sem, RWSEM_NONSPINNABLE))
atomic_long_andnot(RWSEM_NONSPINNABLE, &sem->owner);
}
/*
* This function is called when the reader fails to acquire the lock via
* optimistic spinning. In this case we will still attempt to do a trylock
* when comparing the rwsem state right now with the state when entering
* the slowpath indicates that the reader is still in a valid reader phase.
* This happens when the following conditions are true:
*
* 1) The lock is currently reader owned, and
* 2) The lock is previously not reader-owned or the last read owner changes.
*
* In the former case, we have transitioned from a writer phase to a
* reader-phase while spinning. In the latter case, it means the reader
* phase hasn't ended when we entered the optimistic spinning loop. In
* both cases, the reader is eligible to acquire the lock. This is the
* secondary path where a read lock is acquired optimistically.
*
* The reader non-spinnable bit wasn't set at time of entry or it will
* not be here at all.
*/
static inline bool rwsem_reader_phase_trylock(struct rw_semaphore *sem,
unsigned long last_rowner)
{
unsigned long owner = atomic_long_read(&sem->owner);
if (!(owner & RWSEM_READER_OWNED))
return false;
if (((owner ^ last_rowner) & ~RWSEM_OWNER_FLAGS_MASK) &&
rwsem_try_read_lock_unqueued(sem)) {
lockevent_inc(rwsem_opt_rlock2);
lockevent_add(rwsem_opt_fail, -1);
return true;
}
return false;
}
#else
static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem,
unsigned long nonspinnable)
static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)
{
return false;
}
static inline bool rwsem_optimistic_spin(struct rw_semaphore *sem, bool wlock)
static inline bool rwsem_optimistic_spin(struct rw_semaphore *sem)
{
return false;
}
static inline void clear_wr_nonspinnable(struct rw_semaphore *sem) { }
static inline bool rwsem_reader_phase_trylock(struct rw_semaphore *sem,
unsigned long last_rowner)
{
return false;
}
static inline void clear_nonspinnable(struct rw_semaphore *sem) { }
static inline int
rwsem_spin_on_owner(struct rw_semaphore *sem, unsigned long nonspinnable)
rwsem_spin_on_owner(struct rw_semaphore *sem)
{
return 0;
}
@@ -989,36 +889,35 @@ rwsem_spin_on_owner(struct rw_semaphore *sem, unsigned long nonspinnable)
* Wait for the read lock to be granted
*/
static struct rw_semaphore __sched *
rwsem_down_read_slowpath(struct rw_semaphore *sem, int state)
rwsem_down_read_slowpath(struct rw_semaphore *sem, long count, int state)
{
long count, adjustment = -RWSEM_READER_BIAS;
long adjustment = -RWSEM_READER_BIAS;
long rcnt = (count >> RWSEM_READER_SHIFT);
struct rwsem_waiter waiter;
DEFINE_WAKE_Q(wake_q);
bool wake = false;
/*
* Save the current read-owner of rwsem, if available, and the
* reader nonspinnable bit.
* To prevent a constant stream of readers from starving a sleeping
* waiter, don't attempt optimistic lock stealing if the lock is
* currently owned by readers.
*/
waiter.last_rowner = atomic_long_read(&sem->owner);
if (!(waiter.last_rowner & RWSEM_READER_OWNED))
waiter.last_rowner &= RWSEM_RD_NONSPINNABLE;
if (!rwsem_can_spin_on_owner(sem, RWSEM_RD_NONSPINNABLE))
if ((atomic_long_read(&sem->owner) & RWSEM_READER_OWNED) &&
(rcnt > 1) && !(count & RWSEM_WRITER_LOCKED))
goto queue;
/*
* Undo read bias from down_read() and do optimistic spinning.
* Reader optimistic lock stealing.
*/
atomic_long_add(-RWSEM_READER_BIAS, &sem->count);
adjustment = 0;
if (rwsem_optimistic_spin(sem, false)) {
/* rwsem_optimistic_spin() implies ACQUIRE on success */
if (!(count & (RWSEM_WRITER_LOCKED | RWSEM_FLAG_HANDOFF))) {
rwsem_set_reader_owned(sem);
lockevent_inc(rwsem_rlock_steal);
/*
* Wake up other readers in the wait list if the front
* waiter is a reader.
* Wake up other readers in the wait queue if it is
* the first reader.
*/
if ((atomic_long_read(&sem->count) & RWSEM_FLAG_WAITERS)) {
if ((rcnt == 1) && (count & RWSEM_FLAG_WAITERS)) {
raw_spin_lock_irq(&sem->wait_lock);
if (!list_empty(&sem->wait_list))
rwsem_mark_wake(sem, RWSEM_WAKE_READ_OWNED,
@@ -1027,9 +926,6 @@ rwsem_down_read_slowpath(struct rw_semaphore *sem, int state)
wake_up_q(&wake_q);
}
return sem;
} else if (rwsem_reader_phase_trylock(sem, waiter.last_rowner)) {
/* rwsem_reader_phase_trylock() implies ACQUIRE on success */
return sem;
}
queue:
@@ -1045,7 +941,7 @@ queue:
* exit the slowpath and return immediately as its
* RWSEM_READER_BIAS has already been set in the count.
*/
if (adjustment && !(atomic_long_read(&sem->count) &
if (!(atomic_long_read(&sem->count) &
(RWSEM_WRITER_MASK | RWSEM_FLAG_HANDOFF))) {
/* Provide lock ACQUIRE */
smp_acquire__after_ctrl_dep();
@@ -1059,10 +955,7 @@ queue:
list_add_tail(&waiter.list, &sem->wait_list);
/* we're now waiting on the lock, but no longer actively locking */
if (adjustment)
count = atomic_long_add_return(adjustment, &sem->count);
else
count = atomic_long_read(&sem->count);
count = atomic_long_add_return(adjustment, &sem->count);
/*
* If there are no active locks, wake the front queued process(es).
@@ -1071,7 +964,7 @@ queue:
* wake our own waiter to join the existing active readers !
*/
if (!(count & RWSEM_LOCK_MASK)) {
clear_wr_nonspinnable(sem);
clear_nonspinnable(sem);
wake = true;
}
if (wake || (!(count & RWSEM_WRITER_MASK) &&
@@ -1116,19 +1009,6 @@ out_nolock:
return ERR_PTR(-EINTR);
}
/*
* This function is called by the a write lock owner. So the owner value
* won't get changed by others.
*/
static inline void rwsem_disable_reader_optspin(struct rw_semaphore *sem,
bool disable)
{
if (unlikely(disable)) {
atomic_long_or(RWSEM_RD_NONSPINNABLE, &sem->owner);
lockevent_inc(rwsem_opt_norspin);
}
}
/*
* Wait until we successfully acquire the write lock
*/
@@ -1136,26 +1016,17 @@ static struct rw_semaphore *
rwsem_down_write_slowpath(struct rw_semaphore *sem, int state)
{
long count;
bool disable_rspin;
enum writer_wait_state wstate;
struct rwsem_waiter waiter;
struct rw_semaphore *ret = sem;
DEFINE_WAKE_Q(wake_q);
/* do optimistic spinning and steal lock if possible */
if (rwsem_can_spin_on_owner(sem, RWSEM_WR_NONSPINNABLE) &&
rwsem_optimistic_spin(sem, true)) {
if (rwsem_can_spin_on_owner(sem) && rwsem_optimistic_spin(sem)) {
/* rwsem_optimistic_spin() implies ACQUIRE on success */
return sem;
}
/*
* Disable reader optimistic spinning for this rwsem after
* acquiring the write lock when the setting of the nonspinnable
* bits are observed.
*/
disable_rspin = atomic_long_read(&sem->owner) & RWSEM_NONSPINNABLE;
/*
* Optimistic spinning failed, proceed to the slowpath
* and block until we can acquire the sem.
@@ -1224,7 +1095,7 @@ wait:
* without sleeping.
*/
if (wstate == WRITER_HANDOFF &&
rwsem_spin_on_owner(sem, RWSEM_NONSPINNABLE) == OWNER_NULL)
rwsem_spin_on_owner(sem) == OWNER_NULL)
goto trylock_again;
/* Block until there are no active lockers. */
@@ -1266,7 +1137,6 @@ trylock_again:
}
__set_current_state(TASK_RUNNING);
list_del(&waiter.list);
rwsem_disable_reader_optspin(sem, disable_rspin);
raw_spin_unlock_irq(&sem->wait_lock);
lockevent_inc(rwsem_wlock);
@@ -1335,26 +1205,31 @@ static struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem)
/*
* lock for reading
*/
static inline int __down_read_common(struct rw_semaphore *sem, int state)
{
long count;
if (!rwsem_read_trylock(sem, &count)) {
if (IS_ERR(rwsem_down_read_slowpath(sem, count, state)))
return -EINTR;
DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem);
}
return 0;
}
static inline void __down_read(struct rw_semaphore *sem)
{
if (!rwsem_read_trylock(sem)) {
rwsem_down_read_slowpath(sem, TASK_UNINTERRUPTIBLE);
DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem);
} else {
rwsem_set_reader_owned(sem);
}
__down_read_common(sem, TASK_UNINTERRUPTIBLE);
}
static inline int __down_read_interruptible(struct rw_semaphore *sem)
{
return __down_read_common(sem, TASK_INTERRUPTIBLE);
}
static inline int __down_read_killable(struct rw_semaphore *sem)
{
if (!rwsem_read_trylock(sem)) {
if (IS_ERR(rwsem_down_read_slowpath(sem, TASK_KILLABLE)))
return -EINTR;
DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem);
} else {
rwsem_set_reader_owned(sem);
}
return 0;
return __down_read_common(sem, TASK_KILLABLE);
}
static inline int __down_read_trylock(struct rw_semaphore *sem)
@@ -1380,44 +1255,30 @@ static inline int __down_read_trylock(struct rw_semaphore *sem)
/*
* lock for writing
*/
static inline int __down_write_common(struct rw_semaphore *sem, int state)
{
if (unlikely(!rwsem_write_trylock(sem))) {
if (IS_ERR(rwsem_down_write_slowpath(sem, state)))
return -EINTR;
}
return 0;
}
static inline void __down_write(struct rw_semaphore *sem)
{
long tmp = RWSEM_UNLOCKED_VALUE;
if (unlikely(!atomic_long_try_cmpxchg_acquire(&sem->count, &tmp,
RWSEM_WRITER_LOCKED)))
rwsem_down_write_slowpath(sem, TASK_UNINTERRUPTIBLE);
else
rwsem_set_owner(sem);
__down_write_common(sem, TASK_UNINTERRUPTIBLE);
}
static inline int __down_write_killable(struct rw_semaphore *sem)
{
long tmp = RWSEM_UNLOCKED_VALUE;
if (unlikely(!atomic_long_try_cmpxchg_acquire(&sem->count, &tmp,
RWSEM_WRITER_LOCKED))) {
if (IS_ERR(rwsem_down_write_slowpath(sem, TASK_KILLABLE)))
return -EINTR;
} else {
rwsem_set_owner(sem);
}
return 0;
return __down_write_common(sem, TASK_KILLABLE);
}
static inline int __down_write_trylock(struct rw_semaphore *sem)
{
long tmp;
DEBUG_RWSEMS_WARN_ON(sem->magic != sem, sem);
tmp = RWSEM_UNLOCKED_VALUE;
if (atomic_long_try_cmpxchg_acquire(&sem->count, &tmp,
RWSEM_WRITER_LOCKED)) {
rwsem_set_owner(sem);
return true;
}
return false;
return rwsem_write_trylock(sem);
}
/*
@@ -1435,7 +1296,7 @@ static inline void __up_read(struct rw_semaphore *sem)
DEBUG_RWSEMS_WARN_ON(tmp < 0, sem);
if (unlikely((tmp & (RWSEM_LOCK_MASK|RWSEM_FLAG_WAITERS)) ==
RWSEM_FLAG_WAITERS)) {
clear_wr_nonspinnable(sem);
clear_nonspinnable(sem);
rwsem_wake(sem, tmp);
}
}
@@ -1495,6 +1356,20 @@ void __sched down_read(struct rw_semaphore *sem)
}
EXPORT_SYMBOL(down_read);
int __sched down_read_interruptible(struct rw_semaphore *sem)
{
might_sleep();
rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
if (LOCK_CONTENDED_RETURN(sem, __down_read_trylock, __down_read_interruptible)) {
rwsem_release(&sem->dep_map, _RET_IP_);
return -EINTR;
}
return 0;
}
EXPORT_SYMBOL(down_read_interruptible);
int __sched down_read_killable(struct rw_semaphore *sem)
{
might_sleep();
@@ -1605,6 +1480,20 @@ void down_read_nested(struct rw_semaphore *sem, int subclass)
}
EXPORT_SYMBOL(down_read_nested);
int down_read_killable_nested(struct rw_semaphore *sem, int subclass)
{
might_sleep();
rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_);
if (LOCK_CONTENDED_RETURN(sem, __down_read_trylock, __down_read_killable)) {
rwsem_release(&sem->dep_map, _RET_IP_);
return -EINTR;
}
return 0;
}
EXPORT_SYMBOL(down_read_killable_nested);
void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest)
{
might_sleep();