From 4afba44cac69e6b56e49d773ecc4cc473885e2cd Mon Sep 17 00:00:00 2001 From: Nadav Amit Date: Thu, 2 Jun 2022 01:49:09 +0000 Subject: [PATCH] smp: Fix offline cpu check in flush_smp_call_function_queue() stable inclusion from stable-4.19.239 commit bd4ad32e44ea472c83c7c21e5bee29a1bb1c24e8 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I5A6BA CVE: NA -------------------------------- 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 Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20220319072015.1495036-1-namit@vmware.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Yongqiang Liu --- kernel/smp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/smp.c b/kernel/smp.c index 084c8b3a2681..be15d3a57954 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -221,7 +221,7 @@ static void flush_smp_call_function_queue(bool warn_cpu_offline) /* 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()); -- GitLab