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Message-ID: <20100323105707.GA8634@redhat.com> Date: Tue, 23 Mar 2010 11:57:07 +0100 From: Oleg Nesterov <oleg@...hat.com> To: David Howells <dhowells@...hat.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, Alexey Dobriyan <adobriyan@...il.com>, "Eric W. Biederman" <ebiederm@...ssion.com>, Roland McGrath <roland@...hat.com>, linux-kernel@...r.kernel.org Subject: Re: [PATCH -mm 3/3] proc: make task_sig() lockless On 03/23, David Howells wrote: > > Oleg Nesterov <oleg@...hat.com> wrote: > > > task_sig() doesn't need ->siglock. > > Except that the data returned might then be inconsistent because you don't > hold a lock as you read the various bits of it. Yes. From the changelog: Of course, this means we read pending/blocked/etc nonatomically, but I hope this is OK for fs/proc. But I don't think the returned data could be "really" inconsistent from the /bin/ps pov. Yes, it is possible that, say, some signal is seen as both pending and ignored without ->siglock. Or we can report user->sigpending != 0 while pending/shpending are empty. But this looks harmless to me. We never guaranteed /proc/pid/status can't report the "intermediate" state, and I don't think we can confuse the user-space. Do you agree? Or do you think this can make problems ? Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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