NetBSD Problem Report #44387

From www@NetBSD.org  Fri Jan 14 16:47:24 2011
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Date: Fri, 14 Jan 2011 16:47:22 +0000 (UTC)
From: riz@NetBSD.org
Reply-To: riz@NetBSD.org
To: gnats-bugs@NetBSD.org
Subject: some pthread mutex tests fail on ppc platforms
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>Number:         44387
>Category:       port-powerpc
>Synopsis:       some pthread mutex tests fail on ppc platforms
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    port-powerpc-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Jan 14 16:50:00 +0000 2011
>Last-Modified:  Mon Feb 21 21:45:01 +0000 2011
>Originator:     Jeff Rizzo
>Release:        5.99.43
>Organization:
>Environment:
NetBSD powerbookg4 5.99.43 NetBSD 5.99.43 (GENERIC) #1: Fri Jan 14 08:25:34 PST 2011  riz@hack.lan:/Users/riz/Documents/code/netbsd/obj/sys/arch/macppc/compile/GENERIC macppc

>Description:
Using a kernel that is *not* build with "options DIAGNOSTIC", the regression tests in
/usr/tests/lib/libpthread/t_mutex fail on various powerpc platforms.  The failing test basically creates two threads which each increment a variable which is protected by a mutex;  when it fails (it doesn't fail 100% of the time), it looks like both threads are in "parked" state.  (I have also seen one thread parked and one in iowait)

I confirmed this on two different macppc boxes I have, and I have at least one test run from an ofppc box running 5.99.42 (without DIAGNOSTIC).

For whatever reason, building the kernel with DIAGNOSTIC seems to hide the problem.  I have not yet determined why;  no additional output is available.

In case it matters:  one machine has a PPC 7400, one has a 7447, and one has a 750CX CPU.
>How-To-Repeat:
On a machine with a GENERIC kernel:

cd /usr/tests/lib/libpthread
powerbookg4:riz  /usr/tests/lib/libpthread> ./t_mutex mutex2
1: Mutex-test 2
1: Thread 0xffe00000
2: Second thread (0xefa00000). Count is 10000000

<hang indefinitely>

Sometimes it does not hang - frequency of hang seems to vary by machine and kernel.  You may also wish to run the entire pthread test suite from that directory with "atf-run | atf-report".  It will take about 10 minutes (because of the mutex test hangs).  
>Fix:
None given.

>Audit-Trail:
From: "Jeff Rizzo" <riz@netbsd.org>
To: gnats-bugs@gnats.NetBSD.org
Cc: 
Subject: PR/44387 CVS commit: src/tests/lib/libpthread
Date: Mon, 21 Feb 2011 21:43:42 +0000

 Module Name:	src
 Committed By:	riz
 Date:		Mon Feb 21 21:43:41 UTC 2011

 Modified Files:
 	src/tests/lib/libpthread: t_mutex.c

 Log Message:
 mutex2/mutex3 are expected to fail on powerpc because of
 PR port-powerpc/44387.

 XXX the ugly sleep at the end is because ATF will mark an un-triggered
 race condition (ie, the test passes unexpectedly) as a test failure otherwise.


 To generate a diff of this commit:
 cvs rdiff -u -r1.3 -r1.4 src/tests/lib/libpthread/t_mutex.c

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

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