linux-kernel - Re: recv() hangs until SIGCHLD ?

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Message-ID: <20081011093053.GB5541@const.famille.thibault.fr>
Date:	Sat, 11 Oct 2008 11:30:53 +0200
From:	Samuel Thibault <samuel.thibault@...-lyon.org>
To:	David Schwartz <davids@...master.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: recv() hangs until SIGCHLD ?

David Schwartz, le Fri 10 Oct 2008 21:48:45 -0700, a écrit :
> > We are using the Boehm GC which uses the signals SIGXCPU and SIGPWR to
> > pause+restart the threads when running a GC cycle.
> > [...]
> >
> > However, when attaching GDB to our locked thread it seems that even
> > when the GC runs, recv() does not exit (the breakpoint after it is not
> > reached).
> 
> But you've yet to explain why it should return. Was it interrupted by
> a signal?

See quote above.

> Was data received?

No

> Is the socket non-blocking?

No

> Why isn't this expected behavior?  Blocking sockets block, full stop.

But using a signal is a common technique to have it getting unblocked,
since SUS says

« [EINTR] The recv() function was interrupted by a signal that was
caught, before any data was available. »

Samuel
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