diff options
| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2013-08-15 03:24:26 +0400 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2013-09-23 20:18:13 +0400 |
| commit | 9261dd0da6c6432f08670719069449c6efe4f7a9 (patch) | |
| tree | b8c95dd0e4751e3069e9263d6f46b86251d5dc35 /kernel/rcutree_plugin.h | |
| parent | bb311eccbdab974639263060b8452bf304af0b0c (diff) | |
| download | linux-9261dd0da6c6432f08670719069449c6efe4f7a9.tar.xz | |
rcu: Add tracing for rcuo no-CBs CPU wakeup handshake
Lost wakeups from call_rcu() to the rcuo kthreads can result in hangs
that are difficult to diagnose. This commit therefore adds tracing to
help pin down the cause of these hangs.
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>
[ paulmck: Add const per kbuild test robot's advice. ]
Diffstat (limited to 'kernel/rcutree_plugin.h')
| -rw-r--r-- | kernel/rcutree_plugin.h | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index 130c97b027f2..f4ed24b18e77 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -2108,15 +2108,22 @@ static void __call_rcu_nocb_enqueue(struct rcu_data *rdp, /* If we are not being polled and there is a kthread, awaken it ... */ t = ACCESS_ONCE(rdp->nocb_kthread); - if (rcu_nocb_poll | !t) + if (rcu_nocb_poll | !t) { + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, + TPS("WakeNotPoll")); return; + } len = atomic_long_read(&rdp->nocb_q_count); if (old_rhpp == &rdp->nocb_head) { wake_up(&rdp->nocb_wq); /* ... only if queue was empty ... */ rdp->qlen_last_fqs_check = 0; + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WakeEmpty")); } else if (len > rdp->qlen_last_fqs_check + qhimark) { wake_up_process(t); /* ... or if many callbacks queued. */ rdp->qlen_last_fqs_check = LONG_MAX / 2; + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WakeOvf")); + } else { + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WakeNot")); } return; } @@ -2233,10 +2240,15 @@ static int rcu_nocb_kthread(void *arg) wait_event_interruptible(rdp->nocb_wq, rdp->nocb_head); list = ACCESS_ONCE(rdp->nocb_head); if (!list) { + if (!rcu_nocb_poll) + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, + TPS("WokeEmpty")); schedule_timeout_interruptible(1); flush_signals(current); continue; } + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, + TPS("WokeNonEmpty")); /* * Extract queued callbacks, update counts, and wait |