diff options
Diffstat (limited to 'Documentation/futex-requeue-pi.txt')
| -rw-r--r-- | Documentation/futex-requeue-pi.txt | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/Documentation/futex-requeue-pi.txt b/Documentation/futex-requeue-pi.txt index 31b16610c41..77b36f59d16 100644 --- a/Documentation/futex-requeue-pi.txt +++ b/Documentation/futex-requeue-pi.txt @@ -98,7 +98,7 @@ rt_mutex_start_proxy_lock() and rt_mutex_finish_proxy_lock(), which allow the requeue code to acquire an uncontended rt_mutex on behalf of the waiter and to enqueue the waiter on a contended rt_mutex. Two new system calls provide the kernel<->user interface to -requeue_pi: FUTEX_WAIT_REQUEUE_PI and FUTEX_REQUEUE_CMP_PI. +requeue_pi: FUTEX_WAIT_REQUEUE_PI and FUTEX_CMP_REQUEUE_PI. FUTEX_WAIT_REQUEUE_PI is called by the waiter (pthread_cond_wait() and pthread_cond_timedwait()) to block on the initial futex and wait @@ -107,7 +107,7 @@ result of a high-speed collision between futex_wait() and futex_lock_pi(), with some extra logic to check for the additional wake-up scenarios. -FUTEX_REQUEUE_CMP_PI is called by the waker +FUTEX_CMP_REQUEUE_PI is called by the waker (pthread_cond_broadcast() and pthread_cond_signal()) to requeue and possibly wake the waiting tasks. Internally, this system call is still handled by futex_requeue (by passing requeue_pi=1). Before @@ -120,12 +120,12 @@ task as a waiter on the underlying rt_mutex. It is possible that the lock can be acquired at this stage as well, if so, the next waiter is woken to finish the acquisition of the lock. -FUTEX_REQUEUE_PI accepts nr_wake and nr_requeue as arguments, but +FUTEX_CMP_REQUEUE_PI accepts nr_wake and nr_requeue as arguments, but their sum is all that really matters. futex_requeue() will wake or requeue up to nr_wake + nr_requeue tasks. It will wake only as many tasks as it can acquire the lock for, which in the majority of cases should be 0 as good programming practice dictates that the caller of either pthread_cond_broadcast() or pthread_cond_signal() acquire the -mutex prior to making the call. FUTEX_REQUEUE_PI requires that +mutex prior to making the call. FUTEX_CMP_REQUEUE_PI requires that nr_wake=1. nr_requeue should be INT_MAX for broadcast and 0 for signal. |