[Valgrind-users] valgrind blocks whole process on recvmsg()

[Mike A. <man...@ac...>]

Julian and others,

First, thank you for your work on valgrind.  It's really a great tool.

In both valgrind 1.9.6 and the latest from the 12th of October, I have
observed that a single thread of a valgrinded process that calls
recvmsg() can block the entire process, not just the one thread.  There
is a message here from April of this year regarding a DCE RPC server
that I believe was hit by the same bug, but it was misdiagnosed, and
apparently went unsolved.

Please find a short sample program that exploits this:

http://www.gweep.net/~rocko/vgblock.tar.gz

The program has two threads: a looping counter with printf()s, and a
looping, blocking recvmsg() call.  When run normally, the following
output is generated:

[1] thread 1 will count loops with a 0.5 second delay.
[1] 0
[2] thread 2 will block on recvmsg()
[1] 1
[1] 2
[1] 3
[1] 4
[1] 5
[1] 6
[1] 7
[1] 8
... etc.

When run in valgrind, the recvmsg() blocks the whole process:

=3D=3D15065=3D=3D Memcheck, a.k.a. Valgrind, a memory error detector for
x86-linux.
=3D=3D15065=3D=3D Copyright (C) 2002-2003, and GNU GPL'd, by Julian =
Seward.
=3D=3D15065=3D=3D Using valgrind-20030725, a program supervision =
framework for
x86-linux.
=3D=3D15065=3D=3D Copyright (C) 2000-2003, and GNU GPL'd, by Julian =
Seward.
=3D=3D15065=3D=3D Estimated CPU clock rate is 1313 MHz
=3D=3D15065=3D=3D For more details, rerun with: -v
=3D=3D15065=3D=3D=20
[1] thread 1 will count loops with a 0.5 second delay.
[1] 0
[2] thread 2 will block on recvmsg()


I hope there's an easy fix to this!

Thanks,
-Mike=20
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