linux-kernel - Re: pselect/etc semantics

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Date:   Thu, 30 May 2019 12:20:52 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     Deepa Dinamani <deepa.kernel@...il.com>,
        Al Viro <viro@...IV.linux.org.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        arnd@...db.de, dbueso@...e.de, axboe@...nel.dk, dave@...olabs.net,
        e@...24.org, jbaron@...mai.com, linux-fsdevel@...r.kernel.org,
        linux-aio@...ck.org, omar.kilani@...il.com, tglx@...utronix.de,
        stable@...r.kernel.org
Subject: Re: pselect/etc semantics

Oleg Nesterov <oleg@...hat.com> writes:

> On 05/30, Eric W. Biederman wrote:
>>
>> ebiederm@...ssion.com (Eric W. Biederman) writes:
>>
>> > Which means I believe we have a semantically valid change in behavior
>> > that is causing a regression.
>>
>> I haven't made a survey of all of the functions yet but
>> fucntions return -ENORESTARTNOHAND will never return -EINTR and are
>> immune from this problem.
>
> Hmm. handle_signal:
>
> 		case -ERESTARTNOHAND:
> 			regs->ax = -EINTR;
> 			break;
>
> but I am not sure I understand which problem do you mean..

Yes.  My mistake.  I looked at the transparent restart case for when a
signal is not pending and failed to look at what happens when a signal
is delivered.

So yes.  Everything changed does appear to have a behavioral difference
where they can now succeed and not return -EINTR.

Eric