Re: [PATCH 2/2] mm: page allocator: Do not drain per-cpu lists via IPI from page allocator context
From: Peter Zijlstra <hidden>
Date: 2012-01-12 15:08:04
Also in:
linux-fsdevel, lkml
On Thu, 2012-01-12 at 16:51 +0200, Gilad Ben-Yossef wrote:
quoted hunk ↗ jump to hunk
What I can't figure out is why we don't need get/put_online_cpus() pair around each and every call to on_each_cpu everywhere? and if we do, perhaps making it a part of on_each_cpu is the way to go? Something like:diff --git a/kernel/smp.c b/kernel/smp.c index f66a1b2..cfa3882 100644 --- a/kernel/smp.c +++ b/kernel/smp.c@@ -691,11 +691,15 @@ void on_each_cpu(void (*func) (void *info), void*info, int wait) { unsigned long flags; + BUG_ON(in_atomic()); + + get_online_cpus(); preempt_disable();
Your preempt_disable() here serializes against hotplug..
smp_call_function(func, info, wait);
local_irq_save(flags);
func(info);
local_irq_restore(flags);
preempt_enable();
+ put_online_cpus();
}
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