This is a note to let you know that I've just added the patch titled
smp: Process pending softirqs in flush_smp_call_function_from_idle()
to the 5.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
smp-process-pending-softirqs-in-flush_smp_call_funct.patch
and it can be found in the queue-5.11 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 8e44294bbf5435e26831ceb52843313bf4c04394
Author: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Date: Sat Jan 23 21:10:25 2021 +0100
smp: Process pending softirqs in flush_smp_call_function_from_idle()
[ Upstream commit f9d34595ae4feed38856b88769e2ba5af22d2548 ]
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@xxxxxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20210123201027.3262800-2-bigeasy@xxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
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);
}
