From: Al Viro <viro@ZenIV.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Dmitry Vyukov <dvyukov@google.com>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Pavel Emelyanov <xemul@parallels.com>,
Andrew Morton <akpm@linux-foundation.org>,
syzkaller <syzkaller@googlegroups.com>,
Kostya Serebryany <kcc@google.com>,
Alexander Potapenko <glider@google.com>,
Sasha Levin <sasha.levin@oracle.com>
Subject: Re: fs: uninterruptible hang in handle_userfault
Date: Wed, 2 Mar 2016 00:48:46 +0000 [thread overview]
Message-ID: <20160302004845.GF17997@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CA+55aFzakVoCmAptYdCpEEgK9z003Qk-e_RCC-Gc8Tqt3L8+Cw@mail.gmail.com>
On Tue, Mar 01, 2016 at 12:06:49PM -0800, Linus Torvalds wrote:
> So the only access we really care about is the child tid-pointer
> clearing one, and that always happens after PF_EXITING has been set
> afaik.
>
> No other case really matters. If somebody accesses a userfault region
> just as another thread is exiting, we don't care. I don't think it
> would necessarily be wrong to ignore the fault, but I don't think it's
> relevant either, since at that stage the normal "you can signal the
> thread" still works. It's only the child tid access that comes *after*
> we have stopped acceping signals, and that's marked by that
> PF_EXITING.
>
> Or maybe I misunderstood your worry entirely or missed something, and
> my answer above is entirely beside your point. Did you have something
> else in mind?
No, I've misread de_thread()/zap_other_threads(). No objections to the
patch.
next prev parent reply other threads:[~2016-03-02 0:48 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-01 11:29 fs: uninterruptible hang in handle_userfault Dmitry Vyukov
2016-03-01 19:56 ` Linus Torvalds
2016-03-01 19:59 ` Al Viro
2016-03-01 20:06 ` Linus Torvalds
2016-03-02 0:48 ` Al Viro [this message]
2016-03-02 14:55 ` Andrea Arcangeli
2016-03-02 17:03 ` Linus Torvalds
2016-03-02 17:34 ` Andrea Arcangeli
2016-03-03 7:14 ` Sedat Dilek
[not found] ` <CA+55aFzAUx01f31X6KhZMDddzbnN=rsyzV3nLF=C7FS22m9X=Q@mail.gmail.com>
2016-03-03 7:46 ` Sedat Dilek
2016-03-03 12:48 ` Andrea Arcangeli
2016-03-01 20:28 ` Linus Torvalds
2016-03-02 9:16 ` Dmitry Vyukov
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