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