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Date: Fri, 16 Jan 2015 20:27:57 +0100 From: "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com> To: Thomas Gleixner <tglx@...utronix.de> CC: mtk.manpages@...il.com, Ingo Molnar <mingo@...e.hu>, Darren Hart <darren@...art.com>, lkml <linux-kernel@...r.kernel.org> Subject: [PATCH 1/2] doc: Fix misnamed FUTEX_CMP_REQUEUE_PI 'op' constants From: Michael Kerrisk <mtk.manpages@...il.com> FUTEX_CMP_REQUEUE_PI was misnamed in two different ways: FUTEX_REQUEUE_CMP_PI and FUTEX_REQUEUE_PI. The existence of two different misnamings leaves the reader wondering if we are talking about two different operations. Furthermore, the misnamings mean that grepping the source for the correct name (which doesn't appear at all) won't find this documentation file. Signed-off-by: Michael Kerrisk <mtk.manpages@...il.com> --- Documentation/futex-requeue-pi.txt | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/Documentation/futex-requeue-pi.txt b/Documentation/futex-requeue-pi.txt index 31b1661..77b36f5 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. -- 1.9.3 -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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