[Bug libgomp/38270] New: libgomp test failures due to missing memory barrier

[Bug libgomp/38270] New: libgomp test failures due to missing memory barrier

[janis at gcc dot gnu dot org]

Libgomp test libgomp.c/atomic-3.c started failing with wrong answers on power5
and power6 systems for -m32, and tests nqueens-1.c and sort-1.c started hanging
intermittently for both -m32 and -m64 on those systems, with the addition of
r139969, which removes the memory barrier from rs6000_split_lock_test_and_set. 
Adding back the memory barrier allows those tests to pass again.

David Edelsohn told me that sync_lock_test_and_set does not require the
stricter semantics of a memory barrier and if libgomp needs the memory barrier
then it must emit one itself.

The patch submission for r139969,
http://gcc.gnu.org/ml/gcc/2008-09/msg00038.html, has followups from David and
from Richard Henderson briefly discussing the semantics of
sync_lock_test_and_set.


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           Summary: libgomp test failures due to missing memory barrier
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libgomp
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: janis at gcc dot gnu dot org
GCC target triplet: powerpc64-unknown-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38270

[Bug libgomp/38270] libgomp test failures due to missing memory barrier

[hjl dot tools at gmail dot com]

------- Comment #1 from hjl dot tools at gmail dot com  2008-11-26 15:46 -------
This may be related to PR 37938. You may try similar fix for Linux/ia64.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38270

[Bug libgomp/38270] libgomp test failures due to missing memory barrier

[janis at gcc dot gnu dot org]

------- Comment #2 from janis at gcc dot gnu dot org  2008-11-26 17:39 -------
This is the same problem as in PR37938, as H.J. said, but for powerpc*-linux. 
I'll try copying the ia64 solution.

I see that my objections to having a separate libgomp mutex.h for powerpc have
already been raised by Steve Ellcey and addressed in the mailing list.


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janis at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |janis at gcc dot gnu dot org
                   |dot org                     |
             Status|UNCONFIRMED                 |ASSIGNED
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2008-11-26 17:39:34
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38270

[Bug libgomp/38270] libgomp test failures due to missing memory barrier

[janis at gcc dot gnu dot org]

------- Comment #3 from janis at gcc dot gnu dot org  2008-11-26 22:08 -------
I'm about to take off for a long holiday weekand and haven't finished testing,
but it fixes the test failures to copy mutex.h from libgomp/config/linux/ia64
to libgomp/config/linux/powerpc and update the comments.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38270

[Bug libgomp/38270] libgomp test failures due to missing memory barrier

[janis at gcc dot gnu dot org]

------- Comment #4 from janis at gcc dot gnu dot org  2008-12-02 00:20 -------
Subject: Bug 38270

Author: janis
Date: Tue Dec  2 00:18:56 2008
New Revision: 142341

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=142341
Log:
        PR libgomp/38270
        * config/linux/powerpc/mutex.h: New.

Added:
    trunk/libgomp/config/linux/powerpc/mutex.h
Modified:
    trunk/libgomp/ChangeLog


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38270

[Bug libgomp/38270] libgomp test failures due to missing memory barrier

[janis at gcc dot gnu dot org]

------- Comment #5 from janis at gcc dot gnu dot org  2008-12-02 00:50 -------
Fixed.


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janis at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38270

[Bug libgomp/38270] libgomp test failures due to missing memory barrier

[janis at gcc dot gnu dot org]

------- Comment #6 from janis at gcc dot gnu dot org  2008-12-19 19:43 -------
Created an attachment (id=16947)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=16947&action=view)
final patch

This was the final patch; it wasn't submitted to gcc-patches, but was written
based on a suggestion from Jakub.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38270