All of lore.kernel.org
 help / color / mirror / Atom feed
From: Jakub Jelinek <jakub@redhat.com>
To: mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org,
	torvalds@linux-foundation.org, peterz@infradead.org,
	stable@vger.kernel.org, steven@uplinklabs.net,
	rostedt@goodmis.org, akpm@linux-foundation.org,
	tglx@linutronix.de, oleg@redhat.com, rth@twiddle.net
Cc: linux-tip-commits@vger.kernel.org
Subject: Re: [tip:x86/urgent] compiler/gcc4: Make quirk for asm_volatile_goto( ) unconditional
Date: Thu, 13 Feb 2014 12:55:52 +0100	[thread overview]
Message-ID: <20140213115552.GU20378@tucnak.redhat.com> (raw)
In-Reply-To: <tip-a9f180345f5378ac87d80ed0bea55ba421d83859@git.kernel.org>

On Thu, Feb 13, 2014 at 03:37:08AM -0800, tip-bot for Steven Noonan wrote:
> Commit-ID:  a9f180345f5378ac87d80ed0bea55ba421d83859
> Gitweb:     http://git.kernel.org/tip/a9f180345f5378ac87d80ed0bea55ba421d83859
> Author:     Steven Noonan <steven@uplinklabs.net>
> AuthorDate: Wed, 12 Feb 2014 23:01:07 -0800
> Committer:  Ingo Molnar <mingo@kernel.org>
> CommitDate: Thu, 13 Feb 2014 12:34:05 +0100
> 
> compiler/gcc4: Make quirk for asm_volatile_goto() unconditional
> 
> I started noticing problems with KVM guest destruction on Linux
> 3.12+, where guest memory wasn't being cleaned up. I bisected it
> down to the commit introducing the new 'asm goto'-based atomics,
> and found this quirk was later applied to those.
> 
> Unfortunately, even with GCC 4.8.2 (which ostensibly fixed the
> known 'asm goto' bug) I am still getting some kind of
> miscompilation. If I enable the asm_volatile_goto quirk for my
> compiler, KVM guests are destroyed correctly and the memory is
> cleaned up.

BTW, which exact 4.8.2 were you using?
The last known asm goto bug has been fixed on October, 10th, 2013:
http://gcc.gnu.org/PR58670
so before the October, 16th, 2013 4.8.2 release.  But already since
May 31th, 2013 the tip of the 4.8 GCC branch has been announcing itself
as 4.8.2 prerelease.  While some distribution versions of GCC announce
themselves as the new version only starting from the release date,
i.e. snapshots in between 4.8.1 release and 4.8.2 release announce
themselves as 4.8.1, in other distributions or upstream it announces itself
as 4.8.2.  So, if you are using the latter and a snapshot in between May
31th, 2013 and October, 10th, 2013, then you could see gcc patchlevel 2,
yet have a gcc with that bug unfixed.
So, if the kernel doesn't use a runtime test/configure test to check for
this issue, but instead just relies on the patchlevel version, the only
safe way would be to look for GCC >= 4.9 or GCC 4.8 with patchlevel > 2
rather than > 1.

	Jakub

  reply	other threads:[~2014-02-13 11:56 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-10-12 17:10 [GIT PULL] compiler/gcc4: Add quirk for 'asm goto' miscompilation bug Ingo Molnar
2014-02-13  3:09 ` Steven Noonan
2014-02-13  4:11   ` Linus Torvalds
2014-02-13  4:53     ` [PATCH] compiler/gcc4: make quirk for asm_volatile_goto unconditional Steven Noonan
2014-02-13  6:48       ` Mike Galbraith
2014-02-13  7:01         ` [PATCH v2] " Steven Noonan
2014-02-13 11:37           ` [tip:x86/urgent] compiler/gcc4: Make quirk for asm_volatile_goto( ) unconditional tip-bot for Steven Noonan
2014-02-13 11:55             ` Jakub Jelinek [this message]
2014-02-13 13:44               ` Steven Noonan
2014-07-10 15:00               ` Vlastimil Babka
2014-02-13  7:48     ` [GIT PULL] compiler/gcc4: Add quirk for 'asm goto' miscompilation bug Jakub Jelinek
2014-02-13  9:43     ` Ingo Molnar

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=20140213115552.GU20378@tucnak.redhat.com \
    --to=jakub@redhat.com \
    --cc=akpm@linux-foundation.org \
    --cc=hpa@zytor.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-tip-commits@vger.kernel.org \
    --cc=mingo@kernel.org \
    --cc=oleg@redhat.com \
    --cc=peterz@infradead.org \
    --cc=rostedt@goodmis.org \
    --cc=rth@twiddle.net \
    --cc=stable@vger.kernel.org \
    --cc=steven@uplinklabs.net \
    --cc=tglx@linutronix.de \
    --cc=torvalds@linux-foundation.org \
    --subject='Re: [tip:x86/urgent] compiler/gcc4: Make quirk for asm_volatile_goto( ) unconditional' \
    /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

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.