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Subject: Re: [PATCH v2] signal: Adjust error codes according to restore_user_sigmask()
From:   Deepa Dinamani <deepa.kernel@gmail.com>
In-Reply-To: <ea7a1808990a4c319faa38d5d08d8f19@AcuMS.aculab.com>
Date:   Tue, 28 May 2019 04:37:46 -0700
Cc:     Oleg Nesterov <oleg@redhat.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Arnd Bergmann <arnd@arndb.de>,
        "dbueso@suse.de" <dbueso@suse.de>,
        "axboe@kernel.dk" <axboe@kernel.dk>,
        Davidlohr Bueso <dave@stgolabs.net>, Eric Wong <e@80x24.org>,
        Jason Baron <jbaron@akamai.com>,
        Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
        linux-aio <linux-aio@kvack.org>,
        Omar Kilani <omar.kilani@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
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References: <20190522161407.GB4915@redhat.com> <CABeXuvpjrW5Gt95JC-_rYkOA=6RCD5OtkEQdwZVVqGCE3GkQOQ@mail.gmail.com> <4f7b6dbeab1d424baaebd7a5df116349@AcuMS.aculab.com> <20190523145944.GB23070@redhat.com> <345cfba5edde470f9a68d913f44fa342@AcuMS.aculab.com> <20190523163604.GE23070@redhat.com> <f0eced5677c144debfc5a69d0d327bc1@AcuMS.aculab.com> <CABeXuvo-wey+NHWb4gi=FSRrjJOKkVcLPQ-J+dchJeHEbhGQ6g@mail.gmail.com> <20190524141054.GB2655@redhat.com> <CABeXuvqSzy+v=3Y5NnMmfob7bvuNkafmdDqoex8BVENN3atqZA@mail.gmail.com> <20190524163310.GG2655@redhat.com> <CABeXuvrUKZnECj+NgLdpe5uhKBEmSynrakD-3q9XHqk8Aef5UQ@mail.gmail.com> <ea7a1808990a4c319faa38d5d08d8f19@AcuMS.aculab.com>
To:     David Laight <David.Laight@aculab.com>
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> On May 28, 2019, at 2:12 AM, David Laight <David.Laight@aculab.com> wrote:=

>=20
> From: Deepa Dinamani
>> Sent: 24 May 2019 18:02
> ...
>> Look at the code before 854a6ed56839a:
>>=20
>> /*
>>       * If we changed the signal mask, we need to restore the original on=
e.
>>       * In case we've got a signal while waiting, we do not restore the
>>       * signal mask yet, and we allow do_signal() to deliver the signal o=
n
>>       * the way back to userspace, before the signal mask is restored.
>>       */
>>      if (sigmask) {
>>             ####### This err has not been changed since ep_poll()
>>             ####### So if there is a signal before this point, but
>> err =3D 0, then we goto else.
>>              if (err =3D=3D -EINTR) {
>>                      memcpy(&current->saved_sigmask, &sigsaved,
>>                             sizeof(sigsaved));
>>                      set_restore_sigmask();
>>              } else
>>                    ############ This is a problem if there is signal
>> pending that is sigmask should block.
>>                    ########### This is the whole reason we have
>> current->saved_sigmask?
>>                      set_current_blocked(&sigsaved);
>>      }
>=20
> What happens if all that crap is just deleted (I presume from the
> bottom of ep_wait()) ?

Hmm, you have to update the saved_sigmask or the sigmask.

> I'm guessing that on the way back to userspace signal handlers for
> signals enabled in the process's current mask (the one specified
> to epoll_pwait) get called.
> Then the signal mask is loaded from current->saved_sigmask and
> and enabled signal handlers are called again.

Who is saving this saved_sigmask that is being restored on the way back?

> No special code there that depends on the syscall result, errno
> of the syscall number.

I didn=E2=80=99t say this has anything to do with errno.

-Deepa=20