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authorTorvald Riegel <triegel@redhat.com>2016-12-22 10:20:43 +0100
committerTorvald Riegel <triegel@redhat.com>2017-01-13 17:16:07 +0100
commit65810f0ef05e8c9e333f17a44e77808b163ca298 (patch)
tree09928382f6015251c3b351650204f65fc8d6ec21 /ChangeLog
parentf32941d80c7f532031061f8dd4704fab9c275cfe (diff)
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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 'ChangeLog')
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diff --git a/ChangeLog b/ChangeLog
index 5cdf71a..bf7b236 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,30 @@
+2016-01-13 Torvald Riegel <triegel@redhat.com>
+
+ [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.
+
2017-01-13 Tulio Magno Quites Machado Filho <tuliom@linux.vnet.ibm.com>
* sysdeps/powerpc/fpu/libm-test-ulps: Regenerated.