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rcu: Add tracing to rcu_gp_kthread()

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This commit adds tracing to the rcu_gp_kthread() function in order to
help trace down hangs potentially involving this kthread.

Reported-by: Clark Williams <williams@redhat.com>
Reported-by: Carsten Emde <C.Emde@osadl.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney
2013-09-23 09:16:14 -07:00
parent 591c6d1710
commit 63c4db78e8
2 changed files with 37 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files
kernel/rcutree.c
+18
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@@ -1480,6 +1480,9 @@ static int __noreturn rcu_gp_kthread(void *arg)
/* Handle grace-period start. */
for (;;) {
trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum),
TPS("reqwait"));
wait_event_interruptible(rsp->gp_wq,
ACCESS_ONCE(rsp->gp_flags) &
RCU_GP_FLAG_INIT);
@@ -1487,6 +1490,9 @@ static int __noreturn rcu_gp_kthread(void *arg)
break;
cond_resched();
flush_signals(current);
trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum),
TPS("reqwaitsig"));
}
/* Handle quiescent-state forcing. */
@@ -1500,6 +1506,9 @@ static int __noreturn rcu_gp_kthread(void *arg)
for (;;) {
if (!ret)
rsp->jiffies_force_qs = jiffies + j;
trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum),
TPS("fqswait"));
ret = wait_event_interruptible_timeout(rsp->gp_wq,
((gf = ACCESS_ONCE(rsp->gp_flags)) &
RCU_GP_FLAG_FQS) ||
@@ -1513,12 +1522,21 @@ static int __noreturn rcu_gp_kthread(void *arg)
/* If time for quiescent-state forcing, do it. */
if (ULONG_CMP_GE(jiffies, rsp->jiffies_force_qs) ||
(gf & RCU_GP_FLAG_FQS)) {
trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum),
TPS("fqsstart"));
fqs_state = rcu_gp_fqs(rsp, fqs_state);
trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum),
TPS("fqsend"));
cond_resched();
} else {
/* Deal with stray signal. */
cond_resched();
flush_signals(current);
trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum),
TPS("fqswaitsig"));
}
j = jiffies_till_next_fqs;
if (j > HZ) {