This is a note to let you know that I've just added the patch titled sched/membarrier: fix missing local execution of ipi_sync_rq_state() to the 5.4-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: sched-membarrier-fix-missing-local-execution-of-ipi_sync_rq_state.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From ce29ddc47b91f97e7f69a0fb7cbb5845f52a9825 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> Date: Wed, 17 Feb 2021 11:56:51 -0500 Subject: sched/membarrier: fix missing local execution of ipi_sync_rq_state() From: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> commit ce29ddc47b91f97e7f69a0fb7cbb5845f52a9825 upstream. The function sync_runqueues_membarrier_state() should copy the membarrier state from the @mm received as parameter to each runqueue currently running tasks using that mm. However, the use of smp_call_function_many() skips the current runqueue, which is unintended. Replace by a call to on_each_cpu_mask(). Fixes: 227a4aadc75b ("sched/membarrier: Fix p->mm->membarrier_state racy load") Reported-by: Nadav Amit <nadav.amit@xxxxxxxxx> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx # 5.4.x+ Link: https://lore.kernel.org/r/74F1E842-4A84-47BF-B6C2-5407DFDD4A4A@xxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- kernel/sched/membarrier.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) --- a/kernel/sched/membarrier.c +++ b/kernel/sched/membarrier.c @@ -265,9 +265,7 @@ static int sync_runqueues_membarrier_sta } rcu_read_unlock(); - preempt_disable(); - smp_call_function_many(tmpmask, ipi_sync_rq_state, mm, 1); - preempt_enable(); + on_each_cpu_mask(tmpmask, ipi_sync_rq_state, mm, true); free_cpumask_var(tmpmask); cpus_read_unlock(); Patches currently in stable-queue which might be from mathieu.desnoyers@xxxxxxxxxxxx are queue-5.4/sched-membarrier-fix-missing-local-execution-of-ipi_sync_rq_state.patch