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Re: [RFC PATCH] kernel/signal.c: avoid BUG_ON with SIG128 (MIPS)

To: James Hogan <james.hogan@imgtec.com>
Subject: Re: [RFC PATCH] kernel/signal.c: avoid BUG_ON with SIG128 (MIPS)
From: Denys Vlasenko <vda.linux@googlemail.com>
Date: Fri, 28 Jun 2013 22:03:56 +0200
Cc: Oleg Nesterov <oleg@redhat.com>, David Daney <ddaney.cavm@gmail.com>, LKML <linux-kernel@vger.kernel.org>, linux-mips@linux-mips.org, Ralf Baechle <ralf@linux-mips.org>, Al Viro <viro@zeniv.linux.org.uk>, Andrew Morton <akpm@linux-foundation.org>, Kees Cook <keescook@chromium.org>
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References: <1369846916-13202-1-git-send-email-james.hogan@imgtec.com> <20130529173634.GA2020@redhat.com> <CAAG0J9_yJd5mf0t7whnKDYtf0AdZDnErjOgUga7t0p3TEL_9YQ@mail.gmail.com>
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On Wednesday 29 May 2013 23:56, James Hogan wrote:
> On 29 May 2013 18:36, Oleg Nesterov <oleg@redhat.com> wrote:
> > On 05/29, David Daney wrote:
> >>
> >> On 05/29/2013 10:01 AM, James Hogan wrote:
> >>> MIPS has 128 signals, the highest of which has the number 128. The
> >>
> >> I wonder if we should change the ABI and reduce the number of signals to
> >> 127 instead of this patch.
> >
> > Same thoughts...
> 
> I'll give it a try. I wouldn't have thought it'd break anything, but
> you never know. glibc (incorrectly) sets [__]SIGRTMAX to 127 already.
> On the other hand uClibc sets it to 128, so anything built against
> uClibc that uses signals SIGRTMAX-n (where n may be 0) or uses an
> excessive number of rt signals starting from SIGRTMIN (sounds
> unlikely) could well need an updated uClibc (or a full rebuild if it's
> crazy enough to use __SIGRTMAX).

Fixed in uclibc git: _NSIG is 128, __SIGRTMAX is 127
(_NSIG in libc is not the same as in kernel, but +1).

While at it, added extensive comment why it is so.

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