From: Thomas Gleixner <tglx@linutronix.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Itzcak Pechtalt <itzcak@flashnetworks.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: Race condition in HR timers that cause double insertion and hard lockup -- all latest versions
Date: Tue, 2 Sep 2014 21:08:31 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.10.1409022101080.3333@nanos> (raw)
In-Reply-To: <CA+55aFw9HL4E=3eofs4=hzY=LvWEcKzzJZOTDDTGkeF1_vDcog@mail.gmail.com>
On Tue, 2 Sep 2014, Linus Torvalds wrote:
> On Tue, Sep 2, 2014 at 8:45 AM, Itzcak Pechtalt
> <itzcak@flashnetworks.com> wrote:
> >
> > I opened a bug in https://bugzilla.kernel.org/show_bug.cgi?id=83601 for this subject with full description.
> > There is also a short fix patch for kernel/hrtimer.c file.
> > Even if this bug occurs rary, however it resolves system hard lockup option.
>
> The patch is whitespace-damaged, but with a small oneliner like this
> that doesn't much matter (the timer files moved to kernel/time/ during
> this merge window, so the patch wouldn't apply as-is anyway).
>
> It needs a sign-off (see Documentation/SubmittingPatches), but even
> more importantly it needs to go to the right people for
> double-checking.
>
> But the patch is more broken than whitespace and even lack of
> sign-off. It cannot even have compiled. I'm assuming "timer_state" was
> intended to be "timer->state". Also, every caller but one already has
> "HRTIMER_STATE_CALLBACK" set unconditionally or to the old state in
> "newstate", so I suspect if this patch is the real fix (which I'll
> leave for Thomas to comment more on), afaik the actual problem can
> only happen through migrate_hrtimer_list() which uconditionally sets
> the whole state to HRTIMER_STATE_MIGRATE.
>
> Thomas? Leaving damaged patch quoted below.
Right. It's been fixed long ago and the migrate path cannot suffer
from this problem because at this point a callback running on the dead
cpu would cause the
BUG_ON(hrtimer_callback_running(timer));
a few lines above the remove_hrtimer() call to trigger and send the
machine into lala land.
Thanks,
tglx
prev parent reply other threads:[~2014-09-02 19:08 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-02 15:45 Race condition in HR timers that cause double insertion and hard lockup -- all latest versions Itzcak Pechtalt
2014-09-02 16:08 ` Linus Torvalds
2014-09-02 17:46 ` Itzcak Pechtalt
2014-09-02 19:08 ` Thomas Gleixner [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=alpine.DEB.2.10.1409022101080.3333@nanos \
--to=tglx@linutronix.de \
--cc=itzcak@flashnetworks.com \
--cc=linux-kernel@vger.kernel.org \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).