[Bug build/13844] New: `nptl/sysdeps/unix/sysv/linux/sparc/sparc32/libc-lowlevellock.c' missing in glibc sources

[Bug build/13844] New: `nptl/sysdeps/unix/sysv/linux/sparc/sparc32/libc-lowlevellock.c' missing in glibc sources

[ilmalakhov at yandex dot ru]

http://sourceware.org/bugzilla/show_bug.cgi?id=13844

             Bug #: 13844
           Summary: `nptl/sysdeps/unix/sysv/linux/sparc/sparc32/libc-lowle
                    vellock.c' missing in glibc sources
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: build
        AssignedTo: unassigned@sourceware.org
        ReportedBy: ilmalakhov@yandex.ru
                CC: carlos@systemhalted.org
    Classification: Unclassified


Hi.

 Because of the absence of the sparc32-linux specific version of this file,
`nptl/sysdeps/unix/sysv/linux/libc-lowlevellock.c' is fetched when building
`libc-lowlevellock.o{,s}'. The latter contains just
. . .
#include "lowlevellock.c"

which leads to `nptl/sysdeps/unix/sysv/linux/lowlevellock.c' being actually
compiled instead of
`nptl/sysdeps/unix/sysv/linux/sparc/sparc32/lowlevellock.c'.

 As a consequence a futex can be accessed in a non-atomic way when using libc's
internal locks, e.g. when performing output to the same stream from different
threads.

 For example, when the following test is run on a V8 host, this typically leads
to a deadlock when all threads are waiting for a futex to become free and there
is no one to release it. This happens particularly soon when it's executed this
way at a multi-CPU host:

$ ./test.sparc32 5 > /dev/null


$ cat test.c

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>

void *
handler (void *arg)
{
  for (;;)
    printf ("Thread #%ld\n", (long) arg);

  return NULL;
}

int
main (int argc, char **argv)
{
  size_t i;
  size_t nthreads = (size_t) atoi (argv[1]);
  pthread_t *threads = (pthread_t *) malloc (nthreads * sizeof (pthread_t));

  for (i = 0; i < nthreads; i++)
    pthread_create (&threads[i], NULL, handler, (void *) i);

  for (i = 0; i < nthreads; i++)
    pthread_join (threads[i], NULL);

  free (threads);
  return 0;
}

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[Bug build/13844] `nptl/sysdeps/unix/sysv/linux/sparc/sparc32/libc-lowlevellock.c' missing in glibc sources

[carlos at systemhalted dot org]

http://sourceware.org/bugzilla/show_bug.cgi?id=13844

Carlos O'Donell <carlos at systemhalted dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |UNCONFIRMED
                 CC|                            |davem at davemloft dot net
     Ever Confirmed|1                           |0

--- Comment #1 from Carlos O'Donell <carlos at systemhalted dot org> 2012-03-14 15:51:23 UTC ---
(1) I've added Dave Miller (Sparc maintainer) to the CC.

(2) Please follow "What to put in a report":
http://www.gnu.org/software/libc/bugs.html

(3) No architecture needs to provide libc-lowlevellock.c. The normal sysdep
override mechanism should have selected the sparc32 version of lowlevellock.c
*unless* your configure options failed to cause the selection of sparc32. Given
that you have not provided a full report we don't know why sparc32 was not
selected.

Please include the full log of running `./configure ...` since that will
contain which sysdep directories were selected and in what override order.

Thanks.

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[Bug build/13844] `nptl/sysdeps/unix/sysv/linux/sparc/sparc32/libc-lowlevellock.c' missing in glibc sources

[carlos at systemhalted dot org]

http://sourceware.org/bugzilla/show_bug.cgi?id=13844

Carlos O'Donell <carlos at systemhalted dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at sourceware    |carlos at systemhalted dot
                   |dot org                     |org

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[Bug build/13844] `nptl/sysdeps/unix/sysv/linux/sparc/sparc32/libc-lowlevellock.c' missing in glibc sources

[ilmalakhov at yandex dot ru]

http://sourceware.org/bugzilla/show_bug.cgi?id=13844

--- Comment #2 from Il'ya Malakhov <ilmalakhov at yandex dot ru> 2012-03-15 06:31:22 UTC ---
(In reply to comment #1)
. . .
> (3) . . . The normal sysdep
> override mechanism should have selected the sparc32 version of lowlevellock.c
> *unless* your configure options failed to cause the selection of sparc32. . .
. . .
 And it actually did when compiling lowlevellock.o{,s}, however `#include
"lowlevellock.c"' in the generic version of libc-lowlevellock.c causes the
generic version of lowlevellock.c to be included (because they are in the same
directory) rather than the sparc32 one.

 If you still need a full configure log, I'll provide it a bit later.

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[Bug build/13844] `nptl/sysdeps/unix/sysv/linux/sparc/sparc32/libc-lowlevellock.c' missing in glibc sources

[carlos_odonell at mentor dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13844

Carlos O'Donell <carlos_odonell at mentor dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |carlos_odonell at mentor
                   |                            |dot com
              Flags|                            |review?(davem at davemloft
                   |                            |dot net)

--- Comment #3 from Carlos O'Donell <carlos_odonell at mentor dot com> 2012-03-15 15:14:53 UTC ---
(In reply to comment #2)
> (In reply to comment #1)
> . . .
> > (3) . . . The normal sysdep
> > override mechanism should have selected the sparc32 version of lowlevellock.c
> > *unless* your configure options failed to cause the selection of sparc32. . .
> . . .
>  And it actually did when compiling lowlevellock.o{,s}, however `#include
> "lowlevellock.c"' in the generic version of libc-lowlevellock.c causes the
> generic version of lowlevellock.c to be included (because they are in the same
> directory) rather than the sparc32 one.
> 
>  If you still need a full configure log, I'll provide it a bit later.

No, that makes more sense to me.

I see HPPA has it's own version of libc-lowlevellock.c probably because of this
issue.

I also think ARM might suffer the same problem, it has a lowlevellock.c but no
overriding libc-lowlevellock.c like HPPA.

OK, confirmed, on ARM we are also using the *default* lowlevellock.c e.g.
~~~
nptl/libc-lowlevellock.os:     file format elf32-littlearm


Disassembly of section .text:

00000000 <__lll_lock_wait_private>:
__lll_lock_wait_private():
/opt/codesourcery/arm-verifone-linux-gnueabi/src/glibc/nptl/../nptl/sysdeps/unix/sysv/linux/lowlevellock.c:29
   0:   e92d40f0        push    {r4, r5, r6, r7, lr}
~~~

OK, some big-picture questions.

Dave, Why does sparc have a custom version of lowlevellock.c? Why do any
architectures? The custom versions all seem vaguely similar to the generic
linux version.

If architectures *do* need to override the generic lowlevellock.c without
overriding libc-lowlevellock.c then I think the right solution would be to make
libc-lowlevellock.c use `#include <lowlevellock.c>` such that the sysdep
include mechanism includes the right file.

Il'ya, Would you mind testing that change?

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[Bug build/13844] `nptl/sysdeps/unix/sysv/linux/sparc/sparc32/libc-lowlevellock.c' missing in glibc sources

[davem at davemloft dot net]

http://sourceware.org/bugzilla/show_bug.cgi?id=13844

--- Comment #4 from David S. Miller <davem at davemloft dot net> 2012-03-16 03:51:14 UTC ---
Sparc needs a custom lowlevellock.c on 32-bit sparc because
we have a situation where we don't know if we have the
proper atomic instructions available or not.

For example, if we don't have the v9 compare-and-swap available
we use spinlocks instead.  And for futexes we use a special
24-bit atomic, which embeds the spinlock in the remaining
8-bits.  That's what all of those atomic_compare_and_exchange_val_24_acq
etc. routines are all about.

I'll just add the necessary sparc32/libc-lowlevellock.c file
to fix this, thanks for the report.

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[Bug build/13844] `nptl/sysdeps/unix/sysv/linux/sparc/sparc32/libc-lowlevellock.c' missing in glibc sources

[carlos_odonell at mentor dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13844

Carlos O'Donell <carlos_odonell at mentor dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |2.16
              Flags|review?(davem at davemloft  |review+, review?(joseph at
                   |dot net)                    |codesourcery dot com)

--- Comment #5 from Carlos O'Donell <carlos_odonell at mentor dot com> 2012-03-16 14:27:49 UTC ---
Joseph,

It looks like ARM also needs a libc-lowlevellock.c? Could you please review?

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[Bug build/13844] `nptl/sysdeps/unix/sysv/linux/sparc/sparc32/libc-lowlevellock.c' missing in glibc sources

[joseph at codesourcery dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13844

--- Comment #6 from joseph at codesourcery dot com <joseph at codesourcery dot com> 2012-03-16 14:32:50 UTC ---
I think we should use #include <> in the generic libc-lowlevellock.c 
rather than accumulating copies.

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[Bug build/13844] `nptl/sysdeps/unix/sysv/linux/sparc/sparc32/libc-lowlevellock.c' missing in glibc sources

[davem at davemloft dot net]

http://sourceware.org/bugzilla/show_bug.cgi?id=13844

David S. Miller <davem at davemloft dot net> changed:

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

--- Comment #7 from David S. Miller <davem at davemloft dot net> 2012-03-17 04:00:51 UTC ---
That's what I ended up doing in the end.

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[Bug build/13844] `nptl/sysdeps/unix/sysv/linux/sparc/sparc32/libc-lowlevellock.c' missing in glibc sources

[carlos_odonell at mentor dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13844

Carlos O'Donell <carlos_odonell at mentor dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
              Flags|review?(joseph at           |review+
                   |codesourcery dot com)       |

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[Bug build/13844] `nptl/sysdeps/unix/sysv/linux/sparc/sparc32/libc-lowlevellock.c' missing in glibc sources

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=13844

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
              Flags|                            |security-

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