diff options
Diffstat (limited to 'sysdeps/nptl/futex-internal.h')
| -rw-r--r-- | sysdeps/nptl/futex-internal.h | 86 |
1 files changed, 86 insertions, 0 deletions
diff --git a/sysdeps/nptl/futex-internal.h b/sysdeps/nptl/futex-internal.h index 76921466f0..4feb772f14 100644 --- a/sysdeps/nptl/futex-internal.h +++ b/sysdeps/nptl/futex-internal.h @@ -381,4 +381,90 @@ futex_wake (unsigned int* futex_word, int processes_to_wake, int private) } } +/* The operation checks the value of the futex, if the value is 0, then + it is atomically set to the caller's thread ID. If the futex value is + nonzero, it is atomically sets the FUTEX_WAITERS bit, which signals wrt + other futex owner that it cannot unlock the futex in user space by + atomically by setting its value to 0. + + If more than one wait operations is issued, the enqueueing of the waiters + are done in descending priority order. + + The ABSTIME arguments provides an absolute timeout (measured against the + CLOCK_REALTIME clock). If TIMEOUT is NULL, the operation will block + indefinitely. + + Returns: + + - 0 if woken by a PI unlock operation or spuriously. + - EAGAIN if the futex owner thread ID is about to exit, but has not yet + handled the state cleanup. + - EDEADLK if the futex is already locked by the caller. + - ESRCH if the thread ID int he futex does not exist. + - EINVAL is the state is corrupted or if there is a waiter on the + futex. + - ETIMEDOUT if the ABSTIME expires. +*/ +static __always_inline int +futex_lock_pi (unsigned int *futex_word, const struct timespec *abstime, + int private) +{ + int err = lll_futex_timed_lock_pi (futex_word, abstime, private); + switch (err) + { + case 0: + case -EAGAIN: + case -EINTR: + case -ETIMEDOUT: + case -ESRCH: + case -EDEADLK: + case -EINVAL: /* This indicates either state corruption or that the kernel + found a waiter on futex address which is waiting via + FUTEX_WAIT or FUTEX_WAIT_BITSET. This is reported on + some futex_lock_pi usage (pthread_mutex_timedlock for + instance). */ + return -err; + + case -EFAULT: /* Must have been caused by a glibc or application bug. */ + case -ENOSYS: /* Must have been caused by a glibc bug. */ + /* No other errors are documented at this time. */ + default: + futex_fatal_error (); + } +} + +/* Wakes the top priority waiter that called a futex_lock_pi operation on + the futex. + + Returns the same values as futex_lock_pi under those same conditions; + additionally, returns EPERM when the caller is not allowed to attach + itself to the futex. */ +static __always_inline int +futex_unlock_pi (unsigned int *futex_word, int private) +{ + int err = lll_futex_timed_unlock_pi (futex_word, private); + switch (err) + { + case 0: + case -EAGAIN: + case -EINTR: + case -ETIMEDOUT: + case -ESRCH: + case -EDEADLK: + case -ENOSYS: + case -EPERM: /* The caller is not allowed to attach itself to the futex. + Used to check if PI futexes are supported by the + kernel. */ + return -err; + + case -EINVAL: /* Either due to wrong alignment or due to the timeout not + being normalized. Must have been caused by a glibc or + application bug. */ + case -EFAULT: /* Must have been caused by a glibc or application bug. */ + /* No other errors are documented at this time. */ + default: + futex_fatal_error (); + } +} + #endif /* futex-internal.h */ |