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| author | Alan Modra <amodra@gmail.com> | 2012-09-25 16:30:06 -0500 |
|---|---|---|
| committer | Ryan S. Arnold <rsa@linux.vnet.ibm.com> | 2012-09-25 16:30:06 -0500 |
| commit | 7e2fca8dd22e3bd932581d6479b0c552deff00b6 (patch) | |
| tree | 964db807642e388bfedf3684ab50442a86efadbe | |
| parent | 1c530d024418c75bb61eecf23aea1f4179fbf0fe (diff) | |
| download | glibc-7e2fca8dd22e3bd932581d6479b0c552deff00b6.tar.gz glibc-7e2fca8dd22e3bd932581d6479b0c552deff00b6.tar.xz glibc-7e2fca8dd22e3bd932581d6479b0c552deff00b6.zip | |
Fix bugs in powerpc pthread_once.
Ref gcc.gnu.org/bugzilla/show_bug.cgi?id=52839#c10 Release barriers are needed to ensure that any memory written by init_routine is seen by other threads before *once_control changes. In the case of clear_once_control we need to flush any partially written state.
| -rw-r--r-- | ChangeLog | 8 | ||||
| -rw-r--r-- | nptl/sysdeps/unix/sysv/linux/powerpc/pthread_once.c | 21 |
2 files changed, 24 insertions, 5 deletions
diff --git a/ChangeLog b/ChangeLog index 9e102faf60..1fff9bad72 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,11 @@ +2012-09-25 Alan Modra <amodra@gmail.com> + + * sysdeps/unix/sysv/linux/powerpc/pthread_once.c (__pthread_once): + Add release barrier before setting once_control to say + initialisation is done. Add hints on lwarx. Use macro in + place of isync. + (clear_once_control): Add release barrier. + 2012-09-25 Joseph Myers <joseph@codesourcery.com> [BZ #13629] diff --git a/nptl/sysdeps/unix/sysv/linux/powerpc/pthread_once.c b/nptl/sysdeps/unix/sysv/linux/powerpc/pthread_once.c index 4e3d7bd49a..52ab53f0a9 100644 --- a/nptl/sysdeps/unix/sysv/linux/powerpc/pthread_once.c +++ b/nptl/sysdeps/unix/sysv/linux/powerpc/pthread_once.c @@ -28,6 +28,7 @@ clear_once_control (void *arg) { pthread_once_t *once_control = (pthread_once_t *) arg; + __asm __volatile (__lll_rel_instr); *once_control = 0; lll_futex_wake (once_control, INT_MAX, LLL_PRIVATE); } @@ -47,15 +48,15 @@ __pthread_once (pthread_once_t *once_control, void (*init_routine) (void)) oldval = *once_control; if ((oldval & 2) == 0) *once_control = newval; - Do this atomically. + Do this atomically with an acquire barrier. */ newval = __fork_generation | 1; - __asm __volatile ("1: lwarx %0,0,%3\n" + __asm __volatile ("1: lwarx %0,0,%3" MUTEX_HINT_ACQ "\n" " andi. %1,%0,2\n" " bne 2f\n" " stwcx. %4,0,%3\n" " bne 1b\n" - "2: isync" + "2: " __lll_acq_instr : "=&r" (oldval), "=&r" (tmp), "=m" (*once_control) : "r" (once_control), "r" (newval), "m" (*once_control) : "cr0"); @@ -87,8 +88,18 @@ __pthread_once (pthread_once_t *once_control, void (*init_routine) (void)) pthread_cleanup_pop (0); - /* Add one to *once_control to take the bottom 2 bits from 01 to 10. */ - atomic_increment (once_control); + /* Add one to *once_control to take the bottom 2 bits from 01 to 10. + A release barrier is needed to ensure memory written by init_routine + is seen in other threads before *once_control changes. */ + int tmp; + __asm __volatile (__lll_rel_instr "\n" + "1: lwarx %0,0,%2" MUTEX_HINT_REL "\n" + " addi %0,%0,1\n" + " stwcx. %0,0,%2\n" + " bne- 1b" + : "=&b" (tmp), "=m" (*once_control) + : "r" (once_control), "m" (*once_control) + : "cr0"); /* Wake up all other threads. */ lll_futex_wake (once_control, INT_MAX, LLL_PRIVATE); |