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| author | Tulio Magno Quites Machado Filho <tuliom@linux.vnet.ibm.com> | 2015-07-22 09:26:02 -0300 |
|---|---|---|
| committer | Tulio Magno Quites Machado Filho <tuliom@linux.vnet.ibm.com> | 2015-10-19 16:58:03 -0200 |
| commit | 6ec52bf634b7650b57ff67b5f5053bce8992d549 (patch) | |
| tree | e82562c4a74866a1b7cdabc79311d3a58a6e3729 /NEWS | |
| parent | 44f826e317f28969ea6ca0e87aa4c6b69c819245 (diff) | |
| download | glibc-6ec52bf634b7650b57ff67b5f5053bce8992d549.tar glibc-6ec52bf634b7650b57ff67b5f5053bce8992d549.tar.gz glibc-6ec52bf634b7650b57ff67b5f5053bce8992d549.tar.bz2 glibc-6ec52bf634b7650b57ff67b5f5053bce8992d549.zip | |
PowerPC: Fix a race condition when eliding a lock
The previous code used to evaluate the preprocessor token is_lock_free to
a variable before starting a transaction. This behavior can cause an
error if another thread got the lock (without using a transaction)
between the evaluation of the token and the beginning of the transaction.
This bug can be triggered with the following order of events:
1. The lock accessed by is_lock_free is free.
2. Thread T1 evaluates is_lock_free and stores into register R1 that the
lock is free.
3. Thread T2 acquires the same lock used in is_lock_free.
4. T1 begins the transaction, creating a memory barrier where is_lock_free
is false, but R1 is true.
5. T1 reads R1 and doesn't abort the transaction.
6. T1 calls ELIDE_UNLOCK, which reads false from is_lock_free and decides
to unlock a lock acquired by T2, leading to undefined behavior.
This patch delays the evaluation of is_lock_free to inside a transaction
by moving this part of the code to the macro ELIDE_LOCK.
[BZ #18743]
* sysdeps/powerpc/nptl/elide.h (__elide_lock): Move most of this
code to...
(ELIDE_LOCK): ...here.
(__get_new_count): New function with part of the code from
__elide_lock that updates the value of adapt_count after a
transaction abort.
(__elided_trylock): Moved this code to...
(ELIDE_TRYLOCK): ...here.
Diffstat (limited to 'NEWS')
| -rw-r--r-- | NEWS | 14 |
1 files changed, 7 insertions, 7 deletions
@@ -14,13 +14,13 @@ Version 2.23 16517, 16519, 16520, 16521, 16620, 16734, 16973, 16985, 17118, 17243, 17244, 17250, 17441, 17787, 17886, 17887, 17905, 18084, 18086, 18240, 18265, 18370, 18421, 18480, 18525, 18595, 18589, 18610, 18618, 18647, - 18661, 18674, 18675, 18681, 18724, 18757, 18778, 18781, 18787, 18789, - 18790, 18795, 18796, 18803, 18820, 18823, 18824, 18825, 18857, 18863, - 18870, 18872, 18873, 18875, 18887, 18918, 18921, 18928, 18951, 18952, - 18953, 18956, 18961, 18966, 18967, 18969, 18970, 18977, 18980, 18981, - 18982, 18985, 19003, 19007, 19012, 19016, 19018, 19032, 19046, 19049, - 19050, 19059, 19071, 19074, 19076, 19077, 19078, 19079, 19085, 19086, - 19088, 19094, 19095, 19124, 19125, 19129, 19134, 19137. + 18661, 18674, 18675, 18681, 18724, 18743, 18757, 18778, 18781, 18787, + 18789, 18790, 18795, 18796, 18803, 18820, 18823, 18824, 18825, 18857, + 18863, 18870, 18872, 18873, 18875, 18887, 18918, 18921, 18928, 18951, + 18952, 18953, 18956, 18961, 18966, 18967, 18969, 18970, 18977, 18980, + 18981, 18982, 18985, 19003, 19007, 19012, 19016, 19018, 19032, 19046, + 19049, 19050, 19059, 19071, 19074, 19076, 19077, 19078, 19079, 19085, + 19086, 19088, 19094, 19095, 19124, 19125, 19129, 19134, 19137. * There is now a --disable-timezone-tools configure option for disabling the building and installing of the timezone related utilities (zic, zdump, and |