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Date: Mon, 28 Mar 2011 16:00:49 +0900 (JST) From: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> To: Linus Torvalds <torvalds@...ux-foundation.org> Cc: kosaki.motohiro@...fujitsu.com, Oleg Nesterov <oleg@...hat.com>, linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>, David Rientjes <rientjes@...gle.com>, Rik van Riel <riel@...hat.com>, linux-mm <linux-mm@...ck.org>, Andrey Vagin <avagin@...nvz.org>, Hugh Dickins <hughd@...gle.com>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> Subject: Re: [PATCH 5/5] x86,mm: make pagefault killable > On Thu, Mar 24, 2011 at 10:13 AM, Oleg Nesterov <oleg@...hat.com> wrote: > > > > I am wondering, can't we set FAULT_FLAG_KILLABLE unconditionally > > but check PF_USER when we get VM_FAULT_RETRY? I mean, > > > > if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) { > > if (!(error_code & PF_USER)) > > no_context(...); > > return; > > } > > I agree, we should do this. > > > Probably not... but I can't find any example of in-kernel fault which > > can be broken by -EFAULT if current was killed. > > There's no way that can validly break anything, since any such > codepath has to be able to handle -EFAULT for other reasons anyway. > > The only issue is whether we're ok with a regular write() system call > (for example) not being atomic in the presence of a fatal signal. So > it does change semantics, but I think it changes it in a good way > (technically POSIX requires atomicity, but on the other hand, > technically POSIX also doesn't talk about the process being killed, > and writes would still be atomic for the case where they actually > return. Not to mention NFS etc where writes have never been atomic > anyway, so a program that relies on strict "all or nothing" write > behavior is fundamentally broken to begin with). Ok, I didn't have enough brave. Will do. -- 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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