tracing: Have the trace_event benchmark thread call cond_resched_rcu_qs()

The trace_event benchmark thread runs in kernel space in an infinite loop
while also calling cond_resched() in case anything else wants to schedule
in. Unfortunately, on a PREEMPT kernel, that makes it a nop, in which case,
this will never voluntarily schedule. That will cause synchronize_rcu_tasks()
to forever block on this thread, while it is running.

This is exactly what cond_resched_rcu_qs() is for. Use that instead.
Acked-by: default avatar"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent fcdc7125
...@@ -153,10 +153,18 @@ static int benchmark_event_kthread(void *arg) ...@@ -153,10 +153,18 @@ static int benchmark_event_kthread(void *arg)
trace_do_benchmark(); trace_do_benchmark();
/* /*
* We don't go to sleep, but let others * We don't go to sleep, but let others run as well.
* run as well. * This is bascially a "yield()" to let any task that
* wants to run, schedule in, but if the CPU is idle,
* we'll keep burning cycles.
*
* Note the _rcu_qs() version of cond_resched() will
* notify synchronize_rcu_tasks() that this thread has
* passed a quiescent state for rcu_tasks. Otherwise
* this thread will never voluntarily schedule which would
* block synchronize_rcu_tasks() indefinitely.
*/ */
cond_resched(); cond_resched_rcu_qs();
} }
return 0; return 0;
......
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