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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2018-03-03 01:35:27 +0100 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2018-05-15 19:27:29 +0200 |
| commit | cee4393989333795ae04dc9f3b83a578afe3fca6 (patch) | |
| tree | 9b3afa8f132956c603f83a1fb098f8d30a81d7c1 /kernel/torture.c | |
| parent | rcu: Remove deprecated RCU debugfs tracing code (diff) | |
| download | linux-cee4393989333795ae04dc9f3b83a578afe3fca6.tar.xz linux-cee4393989333795ae04dc9f3b83a578afe3fca6.zip | |
rcu: Rename cond_resched_rcu_qs() to cond_resched_tasks_rcu_qs()
Commit e31d28b6ab8f ("trace: Eliminate cond_resched_rcu_qs() in favor
of cond_resched()") substituted cond_resched() for the earlier call
to cond_resched_rcu_qs(). However, the new-age cond_resched() does
not do anything to help RCU-tasks grace periods because (1) RCU-tasks
is only enabled when CONFIG_PREEMPT=y and (2) cond_resched() is a
complete no-op when preemption is enabled. This situation results
in hangs when running the trace benchmarks.
A number of potential fixes were discussed on LKML
(https://lkml.kernel.org/r/20180224151240.0d63a059@vmware.local.home),
including making cond_resched() not be a no-op; making cond_resched()
not be a no-op, but only when running tracing benchmarks; reverting
the aforementioned commit (which works because cond_resched_rcu_qs()
does provide an RCU-tasks quiescent state; and adding a call to the
scheduler/RCU rcu_note_voluntary_context_switch() function. All were
deemed unsatisfactory, either due to added cond_resched() overhead or
due to magic functions inviting cargo culting.
This commit renames cond_resched_rcu_qs() to cond_resched_tasks_rcu_qs(),
which provides a clear hint as to what this function is doing and
why and where it should be used, and then replaces the call to
cond_resched() with cond_resched_tasks_rcu_qs() in the trace benchmark's
benchmark_event_kthread() function.
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Nicholas Piggin <npiggin@gmail.com>
Diffstat (limited to 'kernel/torture.c')
| -rw-r--r-- | kernel/torture.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/torture.c b/kernel/torture.c index 37b94012a3f8..3de1efbecd6a 100644 --- a/kernel/torture.c +++ b/kernel/torture.c @@ -574,7 +574,7 @@ void stutter_wait(const char *title) { int spt; - cond_resched_rcu_qs(); + cond_resched_tasks_rcu_qs(); spt = READ_ONCE(stutter_pause_test); for (; spt; spt = READ_ONCE(stutter_pause_test)) { if (spt == 1) { |