linux-kernel - Re: [PATCH v2] signal: Adjust error codes according to restore_user

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Message-ID: <20190523145944.GB23070@redhat.com>
Date:   Thu, 23 May 2019 16:59:45 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     'Deepa Dinamani' <deepa.kernel@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Arnd Bergmann <arnd@...db.de>,
        "dbueso@...e.de" <dbueso@...e.de>,
        "axboe@...nel.dk" <axboe@...nel.dk>,
        Davidlohr Bueso <dave@...olabs.net>, Eric Wong <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 <omar.kilani@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH v2] signal: Adjust error codes according to
 restore_user_sigmask()

On 05/23, David Laight wrote:
>
> I'm confused...

Me too. To clarify, the current code is obviously buggy, pselect/whatever
shouldn't return 0 (or anything else) if it was interrupted and we are going
to deliver the signal.

But it seems that Deepa has other concerns which I do not understand at all.

In any case, the signal_pending() check _inside_ restore_user_sigmask() can't
be right, with or without this patch. If nothing else, a signal can come right
after the check.

> So epoll() can return 'success' or 'timeout' (etc) and the handler for SIG_URG
> should still be called.

Not sure I understand... OK, suppose that you do

	block-all-signals;
	ret = pselect(..., sigmask(SIG_URG));

if it returns success/timeout then the handler for SIG_URG should not be called?

or I am totally confused...

Oleg.