From: Andi Kleen <andi@firstfloor.org>
To: Dave Anderson <anderson@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>,
linux-kernel@vger.kernel.org, mingo@elte.hu, jstancek@redhat.com
Subject: Re: [PATCH] x86-64: Prevent gcc from optimizing away venosys_1()
Date: Fri, 3 Jun 2011 23:37:13 +0200 [thread overview]
Message-ID: <20110603213713.GO27166@one.firstfloor.org> (raw)
In-Reply-To: <1972495451.7278.1307136726542.JavaMail.root@zmail05.collab.prod.int.phx2.redhat.com>
On Fri, Jun 03, 2011 at 05:32:06PM -0400, Dave Anderson wrote:
>
>
> ----- Original Message -----
> > > return 0;
> > > }
> > >
> > > -static long __vsyscall(3) venosys_1(void)
> > > +long __vsyscall(3) venosys_1(void)
> >
> > Better add a __used too. Otherwise it can be optimized out again
> > in some builds e.g. when someone enables gc-sections for the linker.
>
> Considering that all of the vsyscall prototypes have this attribute:
>
> #define __vsyscall(nr) \
> __attribute__ ((unused, __section__(".vsyscall_" #nr))) notrace
>
> How would any of them work?
unused is just to prevent warnings I think. used stops the optimizer
from throwing it away.
It would make more sense to drop the unused and add an used. I think
used prevents the warnings too.
-Andi
--
ak@linux.intel.com -- Speaking for myself only.
next prev parent reply other threads:[~2011-06-03 21:37 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <313387488.1201.1307114323524.JavaMail.root@zmail05.collab.prod.int.phx2.redhat.com>
2011-06-03 15:20 ` Dave Anderson
2011-06-03 20:48 ` Andi Kleen
2011-06-03 21:32 ` Dave Anderson
2011-06-03 21:37 ` Andi Kleen [this message]
2011-06-06 17:22 ` Ingo Molnar
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