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From: Stefano Garzarella <sgarzare@redhat.com>
To: Stefan Hajnoczi <stefanha@redhat.com>
Cc: io-uring@vger.kernel.org, Pavel Begunkov <asml.silence@gmail.com>,
	"H.J. Lu" <hjl.tools@gmail.com>,
	libc-alpha@sourceware.org, Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org
Subject: Re: [PATCH liburing] examples/ucontext-cp.c: cope with variable SIGSTKSZ
Date: Thu, 22 Apr 2021 16:22:45 +0200	[thread overview]
Message-ID: <20210422142245.evlxjvfw3emh7ivw@steredhat> (raw)
In-Reply-To: <YIFJDgno7deI5syK@stefanha-x1.localdomain>

+Cc: io-uring@vger.kernel.org
+Cc: Pavel Begunkov <asml.silence@gmail.com>

Original message: 
https://www.spinics.net/lists/linux-block/msg67077.html

On Thu, Apr 22, 2021 at 10:59:42AM +0100, Stefan Hajnoczi wrote:
>On Mon, Apr 19, 2021 at 11:38:07AM -0700, H.J. Lu wrote:
>> On Mon, Apr 19, 2021 at 7:35 AM Stefan Hajnoczi <stefanha@redhat.com> wrote:
>> >
>> > On Tue, Apr 13, 2021 at 04:03:19PM +0100, Stefan Hajnoczi wrote:
>> > > The size of C arrays at file scope must be constant. The following
>> > > compiler error occurs with recent upstream glibc (2.33.9000):
>> > >
>> > >   CC ucontext-cp
>> > >   ucontext-cp.c:31:23: error: variably modified ‘stack_buf’ at file scope
>> > >   31 |         unsigned char stack_buf[SIGSTKSZ];
>> > >      |                       ^~~~~~~~~
>> > >   make[1]: *** [Makefile:26: ucontext-cp] Error 1
>> > >
>> > > The following glibc commit changed SIGSTKSZ from a constant value to a
>> > > variable:
>> > >
>> > >   commit 6c57d320484988e87e446e2e60ce42816bf51d53
>> > >   Author: H.J. Lu <hjl.tools@gmail.com>
>> > >   Date:   Mon Feb 1 11:00:38 2021 -0800
>> > >
>> > >     sysconf: Add _SC_MINSIGSTKSZ/_SC_SIGSTKSZ [BZ #20305]
>> > >   ...
>> > >   +# define SIGSTKSZ sysconf (_SC_SIGSTKSZ)
>> > >
>> > > Allocate the stack buffer explicitly to avoid declaring an array at file
>> > > scope.
>> > >
>> > > Cc: H.J. Lu <hjl.tools@gmail.com>
>> > > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
>> > > ---
>> > > Perhaps the glibc change needs to be revised before releasing glibc 2.34
>> > > since it might break applications. That's up to the glibc folks. It
>> > > doesn't hurt for liburing to take a safer approach that copes with the
>> > > SIGSTKSZ change in any case.
>> >
>> > glibc folks, please take a look. The commit referenced above broke
>> > compilation of liburing's tests. It's possible that applications will
>> > hit similar issues. Can you check whether the SIGSTKSZ change needs to
>> > be reverted/fixed before releasing glibc 2.34?
>> >
>>
>> It won't be changed for glibc 2.34.
>
>Thanks for the response, H.J. and Paul.
>
>In that case liburing needs this patch.
>

I think so:

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>


  reply	other threads:[~2021-04-22 14:22 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-13 15:03 [PATCH liburing] examples/ucontext-cp.c: cope with variable SIGSTKSZ Stefan Hajnoczi
2021-04-19 14:34 ` Stefan Hajnoczi
2021-04-19 18:38   ` H.J. Lu
2021-04-22  9:59     ` Stefan Hajnoczi
2021-04-22 14:22       ` Stefano Garzarella [this message]
2021-04-23 14:13         ` Pavel Begunkov
2021-04-20  0:05   ` Paul Eggert

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