From: Nadav Amit <nadav.amit@gmail.com>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Subject: Local execution of ipi_sync_rq_state() on sync_runqueues_membarrier_state()
Date: Tue, 16 Feb 2021 13:35:23 -0800 [thread overview]
Message-ID: <74F1E842-4A84-47BF-B6C2-5407DFDD4A4A@gmail.com> (raw)
Hello Mathieu,
While trying to find some unrelated by, something in
sync_runqueues_membarrier_state() caught my eye:
static int sync_runqueues_membarrier_state(struct mm_struct *mm)
{
if (atomic_read(&mm->mm_users) == 1 || num_online_cpus() == 1) {
this_cpu_write(runqueues.membarrier_state, membarrier_state);
/*
* For single mm user, we can simply issue a memory barrier
* after setting MEMBARRIER_STATE_GLOBAL_EXPEDITED in the
* mm and in the current runqueue to guarantee that no memory
* access following registration is reordered before
* registration.
*/
smp_mb();
return 0;
}
[ snip ]
smp_call_function_many(tmpmask, ipi_sync_rq_state, mm, 1);
And ipi_sync_rq_state() does:
this_cpu_write(runqueues.membarrier_state,
atomic_read(&mm->membarrier_state));
So my question: are you aware smp_call_function_many() would not run
ipi_sync_rq_state() on the local CPU? Is that the intention of the code?
Thanks,
Nadav
next reply other threads:[~2021-02-16 21:36 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-16 21:35 Nadav Amit [this message]
2021-02-17 14:54 ` Local execution of ipi_sync_rq_state() on sync_runqueues_membarrier_state() Mathieu Desnoyers
2021-03-01 10:16 ` [tip: sched/urgent] sched/membarrier: fix missing local execution of ipi_sync_rq_state() tip-bot2 for Mathieu Desnoyers
2021-03-06 11:42 ` [tip: sched/core] " tip-bot2 for Mathieu Desnoyers
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