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Message-ID: <au-dX8WbBh6c64sy@mail.gmail.com>
Date: Sat, 7 Nov 2026 22:51:27 +0100
From: Luca Kellermann <mailto.luca.kellermann@...il.com>
To: Rich Felker <dalias@...c.org>
Cc: musl@...ts.openwall.com
Subject: Re: [PATCH] thrd_create: inherit signal mask from creating
thread
On Thu, Nov 05, 2026 at 01:54:13PM -0500, Rich Felker wrote:
> On Thu, Nov 05, 2026 at 03:39:51PM +0100, Luca Kellermann wrote:
> > POSIX.1-2024 requires that the new thread created by thrd_create()
> > inherits the signal mask from the creating thread, just like the new
> > thread created by pthread_create().
> >
> > it seems like this was initially the case when thrd_create() was
> > implemented in commit 23614b0fcb4cd4d7b2e4148d3b1887b642169765. commit
> > 04335d9260c076cf4d9264bd93dd3b06c237a639 then changed pthread_create()
> > to always block signals before starting new threads but restoring the
> > signal mask was only done for new threads started by pthread_create()
> > (start()), not for new threads started by thrd_create() (start_c11()).
> > this was before POSIX included threads.h, so it didn't violate any
> > specification back then (the C standard doesn't know signal masks).
>
> Hm, I thought this was intentional. Threads created by library code to
> be transparent to the calling application need to be created with all
> signals masked. Since ISO C has no way to mask signals, the
> thrd_create interface should just do that itself.
At least nothing in the commit message indicates it was intentional.
But I agree that blocking all signals is better.
> If POSIX now requires them to inherit, we should probably change that,
> but it might be worth opening a defect report. Inheriting signal mask
> was really a bug in pthreads, and imposing the same on C11 threads
> where the library code creating the may be POSIX-unaware seems like a
> bad thing.
How do you open a defect report?
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