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Date: Tue, 27 Mar 2018 12:51:54 +0000
From: <Salman.Ahmed@...dmueller.com>
To: <jens.gustedt@...ia.fr>
CC: <musl@...ts.openwall.com>
Subject: AW: segmentation fault on pthread_detach

Hi Jens,

Thanks for the clarification. So I guess with musl I have to remove the pthread_detach (which is redundant anyways after a successful join) or call it only if pthread_join returns an error?

Regards
Salman

-----Ursprüngliche Nachricht-----
Von: Jens Gustedt [mailto:jens.gustedt@...ia.fr]
Gesendet: Dienstag, 27. März 2018 14:33
An: Ahmed, Salman <Salman.Ahmed@...dmueller.com>
Cc: musl@...ts.openwall.com
Betreff: Re: [musl] segmentation fault on pthread_detach

Hello Salman,

On Tue, 27 Mar 2018 12:00:39 +0000 <Salman.Ahmed@...dmueller.com> wrote:

> My application using musl libc runs into a seg fault if I call
> pthread_detach after pthread_join on the same thread. From my
> understanding pthread_detach should return ESRCH if a previous join
> was called on a particular thread. That’s the correct behavior I see
> if I run my program with glibc. But on my LEDE based router I run into
> the seg fault issue. The cross compiling toolchain I use is
> arm_cortex-a9+neon_gcc-5.4.0_musl-1.1.16_eabi. Simple example I used
> for testing is below.

I don't think that your expectation is correct. The POSIX standard
states:

> The behavior is undefined if the value specified by the thread
> argument to pthread_detach() does not refer to a joinable thread.

(a thread that has already been joined is not joinable)

This is for good reasons. The system must be able to dispose of all resources that a thread occupied after it has been joined. The memory will be reused, in particular there may be a new thread that uses the same identifier.

Jens

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