linux-kernel - [PATCH 5.4 157/168] sched/membarrier: fix missing local execution of ipi_sync_rq

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Message-Id: <20210315135555.505804803@linuxfoundation.org>
Date:   Mon, 15 Mar 2021 14:56:29 +0100
From:   gregkh@...uxfoundation.org
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Nadav Amit <nadav.amit@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: [PATCH 5.4 157/168] sched/membarrier: fix missing local execution of ipi_sync_rq_state()

From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>

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@...il.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Cc: stable@...r.kernel.org # 5.4.x+
Link: https://lore.kernel.org/r/74F1E842-4A84-47BF-B6C2-5407DFDD4A4A@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 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();