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Date: Mon, 06 Jul 2020 15:14:43 -0700
From: Hydro Flask <>
To: Rich Felker <>
Subject: Re: Potential deadlock in pthread_kill()

On 2020-07-06 15:00, Rich Felker wrote:
> Yes, I see it clearly now. Sorry it took a while. I have prepared the
> attached patch which I'll push soon if there are no problems.

Needs one more tiny tweak. I noticed that pthread_cancel() calls 
pthread_kill(). That means pthread_kill() must be async-cancel-safe. If 
an asynchronous cancellation happens after pthread_kill() grabs the 
killlock, then it will deadlock because the asynchronous 
pthread_exit(PTHREAD_CANCELED) call will then recursively try to grab 

The solution as far as I can tell is to not just block app signals when 
grabbing killlock, but all signals.

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