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Message-ID: <20200630195409.GH6430@brightrain.aerifal.cx>
Date: Tue, 30 Jun 2020 15:54:10 -0400
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: Potential deadlock in pthread_kill()
On Tue, Jun 30, 2020 at 10:28:50PM +0300, Dmitry Samersoff wrote:
> Hello all,
>
> Does it make sense to trylock and immediately return ESRCH if
> pthread_kill is already in progress?
No, ESRCH is not a valid result for this condition. Moreover killlock
being taken does not tell you that pthread_kill is already in progress
targeting the same thread, just that something that needs the kernel
tid to be valid (kill, cancel, or scheduling changes) or that needs to
change its validity (exiting) is in progress.
Note that for fixing this issue, it won't suffice just to make
pthread_kill block signals. The other places that use the killlock
also need to block signals, to make the lock fully AS-safe.
Rich
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