Subject: Re: PROBLEM:  rt_sigsuspend() does not return EINTR on 2.6.16-rc2+
From: Matthew Grant <grantma@anathoth.gen.nz>
To: David Woodhouse <dwmw2@infradead.org>
Cc: linux-kernel@vger.kernel.org
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	 <1141557862.3764.47.camel@pmac.infradead.org>
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Date: Mon, 06 Mar 2006 21:28:05 +1300
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David,

OK, a major piece of software is broken for mounting removable media. A
kernel upgrade from 2.6.15 SHOULDn't do that. =20

Could you please tell me where go I go next?

Thanks and Cheers,

Matthew Grant

On Sun, 2006-03-05 at 11:24 +0000, David Woodhouse wrote:
> On Sun, 2006-03-05 at 14:26 +1300, Matthew Grant wrote:
> > Problem is that new sys_rt_sigsuspend in kernel/signal.c in 2.6.16-rc2+
> > does not return EINTR.
>=20
> It does for me -- try the trivial test case at
> http://david.woodhou.se/sigsusptest.c
>=20
> If you strace that under old and new kernels you'll see a difference in
> the strace output, but it should be entirely cosmetic. The old code
> would incestuously call do_signal() inside sys_rt_sigsuspend(), and
> would never need to use the mechanism we have for restarting system
> calls. Either it would know it delivered a signal and it would return
> -EINTR, or it would know that it _didn't_, and it would loop for itself.
> Now it behaves like all the other restartable syscalls, and ptrace will
> actually see the -ERESTARTNOHAND return code which later gets converted
> by the signal code either to -EINTR or to an actual restart, as
> appropriate.
>=20
> In short, I think what you've picked up on in the strace output is
> entirely cosmetic, and shouldn't affect the behaviour of the program in
> any way. In each case, it comes back from the signal and goes
> immediately into gettimeofday() and then poll() -- it _has_ come out of
> the sigsuspend(). You then find that poll() gives different results in
> each case, and I'd be inclined to suspect that the _real_ change in
> behaviour goes from that point.
>=20
> > I think David woodhouse may be responsible for this....
>=20
> I read lkml sporadically; usually better to Cc me when I'm to blame :)
>=20
--=20
Matthew Grant <grantma@anathoth.gen.nz>
Matthew's UNIX Box

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