From 7a9b76bb9bf36319aa4f5dd7b21c44febe45b880 Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior Date: Sat, 23 Jan 2021 21:10:25 +0100 Subject: [PATCH] smp: Process pending softirqs in flush_smp_call_function_from_idle() [ Upstream commit 66040b2d5d41f85cb1a752a75260595344c5ec3b ] 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 Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20210123201027.3262800-2-bigeasy@linutronix.de Signed-off-by: Sasha Levin --- kernel/smp.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/smp.c b/kernel/smp.c index 4d17501433be..25240fb2df94 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -14,6 +14,7 @@ #include #include #include +#include #include #include #include @@ -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); }