Re: glibc mutex deadlock in signal handler

From: Junio C Hamano <gitster@pobox.com>
Date: Sep 4, 2015, 21:56 UTC
Message-ID: <xmqq7fo5g85x.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <20150904092355.GA524@sigill.intra.peff.net>

Jeff King <peff@peff.net> writes:

Show 5 quoted lines

> Perhaps we should reconsider whether f4c3edc (vreportf: avoid
> intermediate buffer, 2015-08-11) is a good idea.  Note that snprintf is
> not on the list of safe functions, but I imagine that in practice it is
> fine. Though just avoiding error()/warning() in signal handlers might be
> a more practical solution anyway.

I had exactly the same thought when I read the initial report here.

I wish we can just do "if (in_signal) return;" at the beginning of vreportf(), but we would not want a global variable there, so... ;-)

Further, I briefly hoped that avoiding error/warning in the signal handler codepath would allow us to be more lax around allocations, but I suspect that it unfortunately would not help us that much, as we may be calling these functions in low memory situations.

So let's queue Takashi's patch as-is for now and look at other signal codepaths.

Thanks.