Messages in this thread | | | Date | Mon, 07 Apr 2014 21:57:00 +0200 | From | Toralf Förster <> | Subject | Re: Bisected KVM hang on x86-32 between v3.12 and v3.13 |
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On 04/07/2014 08:59 PM, Frederic Weisbecker wrote: > On Mon, Apr 07, 2014 at 08:16:24PM +0200, Toralf Förster wrote: >> -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 >> >> On 04/07/2014 05:07 PM, Peter Zijlstra wrote: >>> On Mon, Apr 07, 2014 at 05:03:37PM +0200, Peter Zijlstra >>> wrote: >>>> So what I suspect at this point is that because i386 and >>>> x86_64 have a difference in current_thread_info() (i386 is >>>> stack based), we end up setting the TIF_NEED_RESCHED bit on >>>> the wrong stack. >>>> >>>> Now I have some vague memories of propagating the TIF flags >>>> on stack switch, but I cannot remember what arch we did that >>>> for. Let me stare at this a little more. >>>> >>>> Also, IFF this is the case, then the fingered patch above >>>> (and your suggested 'fix') aren't the real curlpit/cure but >>>> simply make it more/less likely to happen. >>>> >>>> Now, Steve had a patch somewhere that would make i386 use >>>> per-cpu variables for current_thread_info() just like x86_64 >>>> already does I think. Let me go find them too. >>> >>> Ohh, goodie, they're already in Linus' tree. Could you see if >>> current git still suffers this problem? >>> >> v3.14-10353-g2b3a8fd works fine AFAICS (BTW the fix is stable >> material, right ?) > > If we are reffering to 198d208df4371734ac4728f69cb585c284d20a15 > (x86: Keep thread_info on thread stack in x86_32) it doesn't carry > a stable tag. > > So to be clear, you are saying that v3.14 is fine but other > release are buggy? Which ones are these? > No, 3.13.x and 3.14 have the issue, latest git is fine and 3.12.x
> If a backport is needed, 198d208df4371734ac4728f69cb585c284d20a15 > looks too large... >
- -- MfG/Sincerely Toralf Förster pgp finger print:1A37 6F99 4A9D 026F 13E2 4DCF C4EA CDDE 0076 E94E -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/
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