diff options
Diffstat (limited to 'nptl')
| -rw-r--r-- | nptl/lowlevellock.c | 21 | ||||
| -rw-r--r-- | nptl/lowlevelrobustlock.c | 9 |
2 files changed, 21 insertions, 9 deletions
diff --git a/nptl/lowlevellock.c b/nptl/lowlevellock.c index 4c093fcb01..e1a203bdd1 100644 --- a/nptl/lowlevellock.c +++ b/nptl/lowlevellock.c @@ -27,10 +27,10 @@ void __lll_lock_wait_private (int *futex) { if (*futex == 2) - lll_futex_wait (futex, 2, LLL_PRIVATE); + lll_futex_wait (futex, 2, LLL_PRIVATE); /* Wait if *futex == 2. */ while (atomic_exchange_acq (futex, 2) != 0) - lll_futex_wait (futex, 2, LLL_PRIVATE); + lll_futex_wait (futex, 2, LLL_PRIVATE); /* Wait if *futex == 2. */ } @@ -40,10 +40,10 @@ void __lll_lock_wait (int *futex, int private) { if (*futex == 2) - lll_futex_wait (futex, 2, private); + lll_futex_wait (futex, 2, private); /* Wait if *futex == 2. */ while (atomic_exchange_acq (futex, 2) != 0) - lll_futex_wait (futex, 2, private); + lll_futex_wait (futex, 2, private); /* Wait if *futex == 2. */ } @@ -75,7 +75,7 @@ __lll_timedlock_wait (int *futex, const struct timespec *abstime, int private) if (rt.tv_sec < 0) return ETIMEDOUT; - /* Wait. */ + /* If *futex == 2, wait until woken or timeout. */ lll_futex_timed_wait (futex, 2, &rt, private); } @@ -83,6 +83,11 @@ __lll_timedlock_wait (int *futex, const struct timespec *abstime, int private) } +/* The kernel notifies a process which uses CLONE_CHILD_CLEARTID via futex + wake-up when the clone terminates. The memory location contains the + thread ID while the clone is running and is reset to zero by the kernel + afterwards. The kernel up to version 3.16.3 does not use the private futex + operations for futex wake-up when the clone terminates. */ int __lll_timedwait_tid (int *tidp, const struct timespec *abstime) { @@ -113,8 +118,10 @@ __lll_timedwait_tid (int *tidp, const struct timespec *abstime) if (rt.tv_sec < 0) return ETIMEDOUT; - /* Wait until thread terminates. The kernel so far does not use - the private futex operations for this. */ + /* If *tidp == tid, wait until thread terminates or the wait times out. + The kernel up to version 3.16.3 does not use the private futex + operations for futex wake-up when the clone terminates. + */ if (lll_futex_timed_wait (tidp, tid, &rt, LLL_SHARED) == -ETIMEDOUT) return ETIMEDOUT; } diff --git a/nptl/lowlevelrobustlock.c b/nptl/lowlevelrobustlock.c index 35258071cf..291d32a5ce 100644 --- a/nptl/lowlevelrobustlock.c +++ b/nptl/lowlevelrobustlock.c @@ -36,14 +36,17 @@ __lll_robust_lock_wait (int *futex, int private) do { + /* If the owner died, return the present value of the futex. */ if (__glibc_unlikely (oldval & FUTEX_OWNER_DIED)) return oldval; + /* Try to put the lock into state 'acquired, possibly with waiters'. */ int newval = oldval | FUTEX_WAITERS; if (oldval != newval && atomic_compare_and_exchange_bool_acq (futex, newval, oldval)) continue; + /* If *futex == 2, wait until woken. */ lll_futex_wait (futex, newval, private); try: @@ -67,7 +70,7 @@ __lll_robust_timedlock_wait (int *futex, const struct timespec *abstime, int tid = THREAD_GETMEM (THREAD_SELF, tid); int oldval = *futex; - /* If the futex changed meanwhile try locking again. */ + /* If the futex changed meanwhile, try locking again. */ if (oldval == 0) goto try; @@ -100,15 +103,17 @@ __lll_robust_timedlock_wait (int *futex, const struct timespec *abstime, return ETIMEDOUT; #endif - /* Wait. */ + /* If the owner died, return the present value of the futex. */ if (__glibc_unlikely (oldval & FUTEX_OWNER_DIED)) return oldval; + /* Try to put the lock into state 'acquired, possibly with waiters'. */ int newval = oldval | FUTEX_WAITERS; if (oldval != newval && atomic_compare_and_exchange_bool_acq (futex, newval, oldval)) continue; + /* If *futex == 2, wait until woken or timeout. */ #if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \ || !defined lll_futex_timed_wait_bitset) lll_futex_timed_wait (futex, newval, &rt, private); |