[Bug nptl/26566] New: nptl/tst-thread-exit-clobber fails on powerpc/powerpc64 with GCC 10.2

[Bug nptl/26566] New: nptl/tst-thread-exit-clobber fails on powerpc/powerpc64 with GCC 10.2

[msc at linux dot ibm.com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26566

            Bug ID: 26566
           Summary: nptl/tst-thread-exit-clobber fails on
                    powerpc/powerpc64 with GCC 10.2
           Product: glibc
           Version: unspecified
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: nptl
          Assignee: unassigned at sourceware dot org
          Reporter: msc at linux dot ibm.com
                CC: drepper.fsp at gmail dot com
  Target Milestone: ---

FAIL: nptl/tst-thread-exit-clobber
original exit status 1
info: unsigned int, direct pthread_exit call
error: tst-thread-exit-clobber.cc:125: not true: value ==
magic_values_double.v4
error: tst-thread-exit-clobber.cc:122: not true: value ==
magic_values_double.v3
error: tst-thread-exit-clobber.cc:119: not true: value ==
magic_values_double.v2
error: tst-thread-exit-clobber.cc:116: not true: value ==
magic_values_double.v1
error: tst-thread-exit-clobber.cc:113: not true: value ==
magic_values_double.v0
error: 5 test failures

I can only reproduce this error on ppc and ppc64, not ppc64le. Also, it works
with GCC 9.3, but fails with GCC 10.2

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[Bug nptl/26566] nptl/tst-thread-exit-clobber fails on powerpc/powerpc64 with GCC 10.2

[adhemerval.zanella at linaro dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26566

Adhemerval Zanella <adhemerval.zanella at linaro dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |adhemerval.zanella at linaro dot o
                   |                            |rg

--- Comment #1 from Adhemerval Zanella <adhemerval.zanella at linaro dot org> ---
I can't reproduce it with gcc-10 from the build-many-glibcs.py on the gccfarm
gcc203.  I also tried with -fstack-clash-protection (as indicated by the test
itself where it was added due
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83641) but it also work as
expected.

In any case, this seems most likely a compiler or libgcc issue, could you check
if it is the case?

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[Bug nptl/26566] nptl/tst-thread-exit-clobber fails on powerpc/powerpc64 with GCC 10.2

[tuliom at ascii dot art.br]

https://sourceware.org/bugzilla/show_bug.cgi?id=26566

Tulio Magno Quites Machado Filho <tuliom at ascii dot art.br> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tuliom at ascii dot art.br

--- Comment #2 from Tulio Magno Quites Machado Filho <tuliom at ascii dot art.br> ---
(In reply to Adhemerval Zanella from comment #1)
> I can't reproduce it with gcc-10 from the build-many-glibcs.py on the
> gccfarm gcc203.

I reproduced on gcc203 with a normal build using:
configure --prefix=/usr --with-cpu=power8 CC=gcc-10 CXX=g++-10

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[Bug nptl/26566] nptl/tst-thread-exit-clobber fails on powerpc/powerpc64 with GCC 10.2

[carlos at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26566

Carlos O'Donell <carlos at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2024-01-22
                 CC|                            |carlos at redhat dot com
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1

--- Comment #3 from Carlos O'Donell <carlos at redhat dot com> ---
This came up again when reviewing the test results for glibc 2.39.

The problem is still present.

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[Bug nptl/26566] nptl/tst-thread-exit-clobber fails on powerpc/powerpc64 with GCC 10.2

[mmatti at linux dot vnet.ibm.com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26566

Manjunath S Matti <mmatti at linux dot vnet.ibm.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bergner at linux dot ibm.com,
                   |                            |mmatti at linux dot vnet.ibm.com

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[Bug nptl/26566] nptl/tst-thread-exit-clobber fails on powerpc/powerpc64 with GCC 10.2

[mmatti at linux dot vnet.ibm.com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26566

--- Comment #4 from Manjunath S Matti <mmatti at linux dot vnet.ibm.com> ---
I observe this failure even with gcc version 13.2.0, but only when glibc is
configured with either --with-cpu=power8 or --with-cpu=power9. But when I
simply configure glibc without mention of any specific Architecture like 

../glibc/configure --enable-debug --prefix=/usr then I am unable to reproduce
this failure.

I suspect that the code generated is causing the issue

107 void
108 check_magic (int index, double value)
109 {
110   switch (index)
111     {
112     case 0:
113       TEST_VERIFY (value == magic_values_double.v0);

Assembly :

  5d4:  7c 69 1b 78     mr      r9,r3
- 5d8:  7f 64 db 78     mr      r4,r27
+ 5d8:  7b 64 00 20     clrldi  r4,r27,32 -->generating this code fixes the
issue
  5dc:  38 60 ff ff     li      r3,-1

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[Bug nptl/26566] nptl/tst-thread-exit-clobber fails on powerpc/powerpc64 with GCC 10.2

[mmatti at linux dot vnet.ibm.com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26566

--- Comment #5 from Manjunath S Matti <mmatti at linux dot vnet.ibm.com> ---
I have some more info here:

I have run make check on both x86 and PPC64le, this particular testcase is
marked as
UNSUPPORTED: nptl/tst-thread-exit-clobber


Also this testcase compares 2 doubles is this ok ?

106 __attribute__ ((noinline, noclone, weak))
107 void
108 check_magic (int index, double value)
109 {
110   switch (index)
111     {
112     case 0:
113       TEST_VERIFY (value == magic_values_double.v0); -> here
114       break;

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[Bug nptl/26566] nptl/tst-thread-exit-clobber fails on powerpc/powerpc64 with GCC 10.2

[mmatti at linux dot vnet.ibm.com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26566

Manjunath S Matti <mmatti at linux dot vnet.ibm.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jeevitha at linux dot ibm.com

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[Bug nptl/26566] nptl/tst-thread-exit-clobber fails on powerpc/powerpc64 with GCC 10.2

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26566

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fweimer at redhat dot com

--- Comment #6 from Florian Weimer <fweimer at redhat dot com> ---
(In reply to Manjunath S Matti from comment #5)
> I have some more info here:
> 
> I have run make check on both x86 and PPC64le, this particular testcase is
> marked as
> UNSUPPORTED: nptl/tst-thread-exit-clobber

I think this happens because it's a C++ tested, and you either do not have a
g++ installed, or libstdc++-static is missing (yes, we should probably fixed
that, and not disable all C++ tests if C++ static linking is unsupported).

> Also this testcase compares 2 doubles is this ok ?
> 
> 106 __attribute__ ((noinline, noclone, weak))
> 107 void
> 108 check_magic (int index, double value)
> 109 {
> 110   switch (index)
> 111     {
> 112     case 0:
> 113       TEST_VERIFY (value == magic_values_double.v0); -> here
> 114       break;

Are you asking because of a general rule that says not to compare floating
point numbers for equality? In this case, we want to make sure that the test
case preserves the bit pattern exactly.

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