Re: [PATCH] SMP signal latency fix up.

From: Ingo Molnar
Date: Fri Nov 07 2003 - 17:29:02 EST

On Fri, 7 Nov 2003, Linus Torvalds wrote:

> (It _looks_ obvious enough, but can you check that there are no pointers
> that we might be following in the "is it running" checks that could be
> stale because we don't hold the runqueue lock any more).

the 'is it running' check is 'task_curr(p)', which in this circumstance is
equivalent to the following test:

per_cpu(runqueues, (cpu)).curr == p

where 'cpu' is p->thread_info->cpu. All pointers dereferenced in this test
are stable, because 1) send_signal() is always called within the siglock,
which serializes with task exit 2) p->thread_info->cpu is always valid for
the same reason.

so this seems to be safe to me.

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