From: Florian Weimer <fw@deneb.enyo.de>
To: enh <enh@google.com>
Cc: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>,
linux-man@vger.kernel.org
Subject: Re: [PATCH] pthread_kill.3: Update to match POSIX.
Date: Wed, 10 Nov 2021 08:14:41 +0100 [thread overview]
Message-ID: <87lf1wjxcu.fsf@mid.deneb.enyo.de> (raw)
In-Reply-To: <CAJgzZooj8VaF_P2YaqwEchR5LEKP_mS379r6GLrexkDen2jGtQ@mail.gmail.com> (enh@google.com's message of "Tue, 9 Nov 2021 15:00:25 -0800")
> any comment from either of the maintainers?
>
> i think what we currently have on this page is factually incorrect,
> and this patch better matches reality.
One more data point:
As of glibc 2.34, pthread_kill in glibc cannot fail with ESRCH anymore
(unless the kernel thread is terminated by a direct system call). And
the race that the signal could be sent to the wrong thread is gone.
> On Tue, Nov 12, 2019 at 10:10 PM Florian Weimer <fw@deneb.enyo.de> wrote:
>>
>> * enh:
>>
>> > On Tue, Nov 12, 2019 at 9:51 PM Florian Weimer <fw@deneb.enyo.de> wrote:
>> >>
>> >> * enh:
>> >>
>> >> > no, because the C library has two choices when a thread exits:
>> >> >
>> >> > 1. unmap the thread.
>> >> >
>> >> > 2. keep the thread around for recycling.
>> >> >
>> >> > if you choose 1 (optimizing for space, like Android), your dereference
>> >> > is illegal.
>> >>
>> >> This choice is only available for threads in a detached state. For
>> >> joinable threads, a conforming implementation cannot immediately
>> >> deallocate all data structures on thread termination. Among other
>> >> things, it has to store the future return value of pthread_join
>> >> somewhere.
>> >
>> > ah, you're trying to say "signal 0 is potentially usable for a
>> > joinable thread that's waiting to be joined"? that's true, but i'm not
>> > sure how that's relevant to this patch. that wouldn't be an "invalid
>> > thread ID" until it's joined.
>>
>> Correct. That's POSIX's argument why ESRCH wouldn't be valid to
>> return here. It's still a forceful loss of information, and
>> particularly annoying since POSIX doesn't specify pthread_tryjoin.
>>
>> But I'm glad we've brought our discussion to a conclusion. 8-)
next prev parent reply other threads:[~2021-11-10 7:22 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-12 20:36 [PATCH] pthread_kill.3: Update to match POSIX enh
2019-11-12 21:38 ` Florian Weimer
2019-11-12 21:40 ` enh
2019-11-12 21:52 ` Florian Weimer
2019-11-12 22:06 ` enh
2019-11-12 22:11 ` Florian Weimer
2019-11-12 22:22 ` enh
2019-11-12 22:28 ` Florian Weimer
2019-11-13 5:27 ` enh
2019-11-13 5:51 ` Florian Weimer
2019-11-13 5:59 ` enh
2019-11-13 6:10 ` Florian Weimer
2021-11-09 23:00 ` enh
2021-11-10 7:14 ` Florian Weimer [this message]
2021-11-12 0:01 ` enh
2021-11-12 13:02 ` Florian Weimer
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