linux-kernel - Re: pselect/etc semantics (Was: [PATCH v2] signal: Adjust error codes according to restore_user

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Message-ID: <20190530144044.GG22536@redhat.com>
Date:   Thu, 30 May 2019 16:40:45 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Deepa Dinamani <deepa.kernel@...il.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>, dbueso@...e.de,
        Jens Axboe <axboe@...nel.dk>,
        Davidlohr Bueso <dave@...olabs.net>, e@...24.org,
        Jason Baron <jbaron@...mai.com>,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        linux-aio <linux-aio@...ck.org>, omar.kilani@...il.com,
        Thomas Gleixner <tglx@...utronix.de>,
        "# 3.4.x" <stable@...r.kernel.org>
Subject: Re: pselect/etc semantics (Was: [PATCH v2] signal: Adjust error
 codes according to restore_user_sigmask())

On 05/30, Arnd Bergmann wrote:
>
> I think this is a nice simplification, but it would help not to mix up the
> minimal regression fix with the rewrite of those functions.

Yes, yes, agreed.

Plus every file touched by this patch asks for more cleanups. Say, do_poll()
should return -ERESTARTNOHAND, not -EINTR, after that we can remove the ugly
EINTR->ERESTARTNOHAND in its callers. And more.

> For the stable
> kernels, I think we want just the addition of the 'bool interrupted' argument
> to restore_user_sigmask()

or simply revert this patch. I will check if this is possible today... At first
glance 854a6ed56839a40f6 fixed another bug by accident, do_pselect() did
"ret == -ERESTARTNOHAND" after "ret = poll_select_copy_remaining()" which can
turn ERESTARTNOHAND into EINTR, but this is simple. I'll check tomorrow.


> > -       ret = set_user_sigmask(ksig.sigmask, &ksigmask, &sigsaved, ksig.sigsetsize);
> > +       ret = set_xxx(ksig.sigmask, ksig.sigsetsize);
> >         if (ret)
> >                 return ret;
> >
> >         ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &ts : NULL);
> > -       restore_user_sigmask(ksig.sigmask, &sigsaved);
> > -       if (signal_pending(current) && !ret)
> > +
> > +       interrupted = signal_pending(current);
> > +       update_xxx(interrupted);
>
> Maybe name this
>
>            restore_saved_sigmask_if(!interrupted);

Yes, I thought about restore_if(), but to me

		restore_saved_sigmask_if(ret != -EINTR);

doesn't look readable... May be

		restore_saved_sigmask_unless(ret == -EINTR);

? but actually I agree with any naming.

> and make restore_saved_sigmask_if() an inline function
> next to restore_saved_sigmask()?

agreed,

> With some of the recent discussions about compat syscall handling,
> I now think that we want to just fold set_compat_user_sigmask()
> into set_user_sigmask()

agreed, and I thought about this too. But again, I'd prefer to do this
and other cleanups later, on top of this patch.

Oleg.