The patch titled
rcu: increment quiescent state counter in ksoftirqd()
has been added to the -mm tree. Its filename is
rcu-increment-quiescent-state-counter-in-ksoftirqd.patch
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Subject: rcu: increment quiescent state counter in ksoftirqd()
From: Eric Dumazet <dada1@xxxxxxxxxxxxx>
If a machine is flooded by network frames, a cpu can loop 100% of its time
inside ksoftirqd() without calling schedule(). This can delay RCU grace
period to insane values.
Adding rcu_qsctr_inc() call in ksoftirqd() solves this problem.
Paul: "This regression was a result of the recent change from "schedule()"
to "cond_resched()", which got rid of that quiescent state in the common
case where a reschedule is not needed".
Signed-off-by: Eric Dumazet <dada1@xxxxxxxxxxxxx>
Reviewed-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/softirq.c | 1 +
1 file changed, 1 insertion(+)
diff -puN kernel/softirq.c~rcu-increment-quiescent-state-counter-in-ksoftirqd kernel/softirq.c
--- a/kernel/softirq.c~rcu-increment-quiescent-state-counter-in-ksoftirqd
+++ a/kernel/softirq.c
@@ -648,6 +648,7 @@ static int ksoftirqd(void * __bind_cpu)
preempt_enable_no_resched();
cond_resched();
preempt_disable();
+ rcu_qsctr_inc((long)__bind_cpu);
}
preempt_enable();
set_current_state(TASK_INTERRUPTIBLE);
_
Patches currently in -mm which might be from dada1@xxxxxxxxxxxxx are
linux-next.patch
rcu-increment-quiescent-state-counter-in-ksoftirqd.patch
softirq-introduce-statistics-for-softirq.patch
proc-export-statistics-for-softirq-to-proc.patch
proc-export-statistics-for-softirq-to-proc-fix.patch
proc-update-document-for-proc-softirqs-and-proc-stat.patch
workqueue-avoid-recursion-in-run_workqueue.patch
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