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| author | Torvald Riegel <triegel@redhat.com> | 2016-12-22 10:20:43 +0100 |
|---|---|---|
| committer | Torvald Riegel <triegel@redhat.com> | 2017-01-13 17:16:07 +0100 |
| commit | 65810f0ef05e8c9e333f17a44e77808b163ca298 (patch) | |
| tree | 09928382f6015251c3b351650204f65fc8d6ec21 /nptl/Makefile | |
| parent | f32941d80c7f532031061f8dd4704fab9c275cfe (diff) | |
| download | glibc-65810f0ef05e8c9e333f17a44e77808b163ca298.tar.gz | |
robust mutexes: Fix broken x86 assembly by removing it
lll_robust_unlock on i386 and x86_64 first sets the futex word to
FUTEX_WAITERS|0 before calling __lll_unlock_wake, which will set the
futex word to 0. If the thread is killed between these steps, then the
futex word will be FUTEX_WAITERS|0, and the kernel (at least current
upstream) will not set it to FUTEX_OWNER_DIED|FUTEX_WAITERS because 0 is
not equal to the TID of the crashed thread.
The lll_robust_lock assembly code on i386 and x86_64 is not prepared to
deal with this case because the fastpath tries to only CAS 0 to TID and
not FUTEX_WAITERS|0 to TID; the slowpath simply waits until it can CAS 0
to TID or the futex_word has the FUTEX_OWNER_DIED bit set.
This issue is fixed by removing the custom x86 assembly code and using
the generic C code instead. However, instead of adding more duplicate
code to the custom x86 lowlevellock.h, the code of the lll_robust* functions
is inlined into the single call sites that exist for each of these functions
in the pthread_mutex_* functions. The robust mutex paths in the latter
have been slightly reorganized to make them simpler.
This patch is meant to be easy to backport, so C11-style atomics are not
used.
[BZ #20985]
* nptl/Makefile: Adapt.
* nptl/pthread_mutex_cond_lock.c (LLL_ROBUST_MUTEX_LOCK): Remove.
(LLL_ROBUST_MUTEX_LOCK_MODIFIER): New.
* nptl/pthread_mutex_lock.c (LLL_ROBUST_MUTEX_LOCK): Remove.
(LLL_ROBUST_MUTEX_LOCK_MODIFIER): New.
(__pthread_mutex_lock_full): Inline lll_robust* functions and adapt.
* nptl/pthread_mutex_timedlock.c (pthread_mutex_timedlock): Inline
lll_robust* functions and adapt.
* nptl/pthread_mutex_unlock.c (__pthread_mutex_unlock_full): Likewise.
* sysdeps/nptl/lowlevellock.h (__lll_robust_lock_wait,
__lll_robust_lock, lll_robust_cond_lock, __lll_robust_timedlock_wait,
__lll_robust_timedlock, __lll_robust_unlock): Remove.
* sysdeps/unix/sysv/linux/i386/lowlevellock.h (lll_robust_lock,
lll_robust_cond_lock, lll_robust_timedlock, lll_robust_unlock): Remove.
* sysdeps/unix/sysv/linux/x86_64/lowlevellock.h (lll_robust_lock,
lll_robust_cond_lock, lll_robust_timedlock, lll_robust_unlock): Remove.
* sysdeps/unix/sysv/linux/sparc/lowlevellock.h (__lll_robust_lock_wait,
__lll_robust_lock, lll_robust_cond_lock, __lll_robust_timedlock_wait,
__lll_robust_timedlock, __lll_robust_unlock): Remove.
* nptl/lowlevelrobustlock.c: Remove file.
* nptl/lowlevelrobustlock.sym: Likewise.
* sysdeps/unix/sysv/linux/i386/lowlevelrobustlock.S: Likewise.
* sysdeps/unix/sysv/linux/x86_64/lowlevelrobustlock.S: Likewise.
Diffstat (limited to 'nptl/Makefile')
| -rw-r--r-- | nptl/Makefile | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/nptl/Makefile b/nptl/Makefile index 9d5738f270..dcb5953325 100644 --- a/nptl/Makefile +++ b/nptl/Makefile @@ -117,7 +117,7 @@ libpthread-routines = nptl-init vars events version pt-interp \ cleanup_defer_compat unwind \ pt-longjmp pt-cleanup\ cancellation \ - lowlevellock lowlevelrobustlock \ + lowlevellock \ lll_timedlock_wait lll_timedwait_tid \ pt-fork pt-vfork \ $(pthread-compat-wrappers) \ @@ -309,7 +309,7 @@ tests-nolibpthread = tst-unload gen-as-const-headers = pthread-errnos.sym \ unwindbuf.sym \ - lowlevelrobustlock.sym pthread-pi-defines.sym + pthread-pi-defines.sym gen-py-const-headers := nptl_lock_constants.pysym pretty-printers := nptl-printers.py |