From: Nadav Amit namit@vmware.com
commit 9e949a3886356fe9112c6f6f34a6e23d1d35407f upstream.
The check in flush_smp_call_function_queue() for callbacks that are sent to offline CPUs currently checks whether the queue is empty.
However, flush_smp_call_function_queue() has just deleted all the callbacks from the queue and moved all the entries into a local list. This checks would only be positive if some callbacks were added in the short time after llist_del_all() was called. This does not seem to be the intention of this check.
Change the check to look at the local list to which the entries were moved instead of the queue from which all the callbacks were just removed.
Fixes: 8d056c48e4862 ("CPU hotplug, smp: flush any pending IPI callbacks before CPU offline") Signed-off-by: Nadav Amit namit@vmware.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Link: https://lore.kernel.org/r/20220319072015.1495036-1-namit@vmware.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/smp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/smp.c +++ b/kernel/smp.c @@ -221,7 +221,7 @@ static void flush_smp_call_function_queu
/* There shouldn't be any pending callbacks on an offline CPU. */ if (unlikely(warn_cpu_offline && !cpu_online(smp_processor_id()) && - !warned && !llist_empty(head))) { + !warned && entry != NULL)) { warned = true; WARN(1, "IPI on offline CPU %d\n", smp_processor_id());