linux-kernel - Re: um: WARNING: at kernel/futex.c:786 __unqueue

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 17 Mar 2011 14:16:42 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	richard -rw- weinberger <richard.weinberger@...il.com>,
	laijs@...fujitsu.com, LKML <linux-kernel@...r.kernel.org>,
	user-mode-linux-devel@...ts.sourceforge.net, dvhart@...ux.intel.com
Subject: Re: um: WARNING: at kernel/futex.c:786 __unqueue_futex

On Thu, 2011-03-17 at 18:02 +0100, Eric Dumazet wrote:
> Le jeudi 17 mars 2011 à 12:55 -0400, Steven Rostedt a écrit :
> > Here, test this patch. I'm in the process of committing it now.
> > It will be two patches, one for the WARN_ON_SMP() change, the other for
> > the futex change.
> > 
> > -- Steve
> > 
> > diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
> > index c2c9ba0..25f1e9e 100644
> > --- a/include/asm-generic/bug.h
> > +++ b/include/asm-generic/bug.h
> > @@ -168,7 +168,7 @@ extern void warn_slowpath_null(const char *file, const int line);
> >  #ifdef CONFIG_SMP
> >  # define WARN_ON_SMP(x)			WARN_ON(x)
> >  #else
> > -# define WARN_ON_SMP(x)			do { } while (0)
> > +# define WARN_ON_SMP(x)			({0;})
> >  #endif
> >  
> 
> You meant :
> 
> # define WARN_ON_SMP(x)			({x;})
> 
> or
> 
> # define WARN_ON_SMP(x)	  do { } while (x, 0)
> 
> ?
> 

Does if (do { } while (x, 0)) work?

And no, on SMP it should always return false. The point is, the warning
is only valid if we are on an SMP box, this is useful for spin_locks()

if (WARN_ON_SMP(!spin_is_locked(lock)))
	fail();

We don't want to fail.

That spin_is_locked(lock) on !SMP returns 0 every time.

-- Steve


--
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/