diff options
| author | Paul E. McKenney | 2018-03-02 16:35:27 -0800 |
|---|---|---|
| committer | Paul E. McKenney | 2018-05-15 10:27:29 -0700 |
| commit | cee4393989333795ae04dc9f3b83a578afe3fca6 (patch) | |
| tree | 9b3afa8f132956c603f83a1fb098f8d30a81d7c1 /kernel/rcu/tree_plugin.h | |
| parent | 6fba2b3767ea6e3e1204855031492415cc4dce4f (diff) | |
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/rcu/tree_plugin.h')
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 12774c4fb546..dfc42c3d52d4 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1598,7 +1598,7 @@ static int rcu_oom_notify(struct notifier_block *self, for_each_online_cpu(cpu) { smp_call_function_single(cpu, rcu_oom_notify_cpu, NULL, 1); - cond_resched_rcu_qs(); + cond_resched_tasks_rcu_qs(); } /* Unconditionally decrement: no need to wake ourselves up. */ @@ -2227,7 +2227,7 @@ static int rcu_nocb_kthread(void *arg) cl++; c++; local_bh_enable(); - cond_resched_rcu_qs(); + cond_resched_tasks_rcu_qs(); list = next; } trace_rcu_batch_end(rdp->rsp->name, c, !!list, 0, 0, 1); |