| Message ID | 20210123201027.3262800-2-bigeasy@linutronix.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | blk-mq: Don't complete in IRQ, use llist_head | expand |
On 2021-01-23 21:10:25 [+0100], To linux-block@vger.kernel.org wrote: > send_call_function_single_ipi() may wake an idle CPU without sending an > IPI. The woken up CPU will process the SMP-functions in > flush_smp_call_function_from_idle(). Any raised softirq from within the > SMP-function call will not be processed. > Should the CPU have no tasks assigned, then it will go back to idle with > pending softirqs and the NOHZ will rightfully complain. > > Process pending softirqs on return from flush_smp_call_function_queue(). > > Fixes: b2a02fc43a1f4 ("smp: Optimize send_call_function_single_ipi()") > Reported-by: Jens Axboe <axboe@kernel.dk> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> A gentle ping. This isn't just a requirement for the series: rps_trigger_softirq() is invoked from smp_call_function_single_async() and raises a softirq. Sebastian
On Sat, Jan 23, 2021 at 09:10:25PM +0100, Sebastian Andrzej Siewior wrote: > send_call_function_single_ipi() may wake an idle CPU without sending an > IPI. The woken up CPU will process the SMP-functions in > flush_smp_call_function_from_idle(). Any raised softirq from within the > SMP-function call will not be processed. > Should the CPU have no tasks assigned, then it will go back to idle with > pending softirqs and the NOHZ will rightfully complain. > > Process pending softirqs on return from flush_smp_call_function_queue(). > > Fixes: b2a02fc43a1f4 ("smp: Optimize send_call_function_single_ipi()") > Reported-by: Jens Axboe <axboe@kernel.dk> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Fair enough. I'll stick this in tip/sched/smp for Jens and merge that into tip/sched/core. Thanks!
On 2021-02-09 11:02:10 [+0100], Peter Zijlstra wrote: > Fair enough. I'll stick this in tip/sched/smp for Jens and merge that > into tip/sched/core. Thank you. > Thanks! Sebastian
diff --git a/kernel/smp.c b/kernel/smp.c index 1b6070bf97bb0..aeb0adfa06063 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -14,6 +14,7 @@ #include <linux/export.h> #include <linux/percpu.h> #include <linux/init.h> +#include <linux/interrupt.h> #include <linux/gfp.h> #include <linux/smp.h> #include <linux/cpu.h> @@ -449,6 +450,9 @@ void flush_smp_call_function_from_idle(void) local_irq_save(flags); flush_smp_call_function_queue(true); + if (local_softirq_pending()) + do_softirq(); + local_irq_restore(flags); }
send_call_function_single_ipi() may wake an idle CPU without sending an IPI. The woken up CPU will process the SMP-functions in flush_smp_call_function_from_idle(). Any raised softirq from within the SMP-function call will not be processed. Should the CPU have no tasks assigned, then it will go back to idle with pending softirqs and the NOHZ will rightfully complain. Process pending softirqs on return from flush_smp_call_function_queue(). Fixes: b2a02fc43a1f4 ("smp: Optimize send_call_function_single_ipi()") Reported-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- kernel/smp.c | 4 ++++ 1 file changed, 4 insertions(+)