From: Andrea Arcangeli <andrea@qumranet.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Lameter <clameter@sgi.com>,
Jack Steiner <steiner@sgi.com>, Robin Holt <holt@sgi.com>,
Nick Piggin <npiggin@suse.de>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
kvm-devel@lists.sourceforge.net,
Kanoj Sarcar <kanojsarcar@yahoo.com>,
Roland Dreier <rdreier@cisco.com>,
Steve Wise <swise@opengridcomputing.com>,
linux-kernel@vger.kernel.org, Avi Kivity <avi@qumranet.com>,
linux-mm@kvack.org, general@lists.openfabrics.org,
Hugh Dickins <hugh@veritas.com>,
akpm@linux-foundation.org, Rusty Russell <rusty@rustcorp.com.au>,
Anthony Liguori <aliguori@us.ibm.com>,
Chris Wright <chrisw@redhat.com>,
Marcelo Tosatti <marcelo@kvack.org>,
Eric Dumazet <dada1@cosmosbay.com>,
"Paul E. McKenney" <paulmck@us.ibm.com>
Subject: [PATCH 06 of 11] rwsem contended
Date: Wed, 07 May 2008 16:35:56 +0200 [thread overview]
Message-ID: <0621238970155f8ff2d6.1210170956@duo.random> (raw)
In-Reply-To: <patchbomb.1210170950@duo.random>
# HG changeset patch
# User Andrea Arcangeli <andrea@qumranet.com>
# Date 1210115132 -7200
# Node ID 0621238970155f8ff2d60ca4996dcdd470f9c6ce
# Parent 20bc6a66a86ef6bd60919cc77ff51d4af741b057
rwsem contended
Add a function to rw_semaphores to check if there are any processes
waiting for the semaphore. Add rwsem_needbreak to sched.h that works
in the same way as spinlock_needbreak().
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrea Arcangeli <andrea@qumranet.com>
diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
--- a/include/linux/rwsem.h
+++ b/include/linux/rwsem.h
@@ -57,6 +57,8 @@ extern void up_write(struct rw_semaphore
*/
extern void downgrade_write(struct rw_semaphore *sem);
+extern int rwsem_is_contended(struct rw_semaphore *sem);
+
#ifdef CONFIG_DEBUG_LOCK_ALLOC
/*
* nested locking. NOTE: rwsems are not allowed to recurse
diff --git a/include/linux/sched.h b/include/linux/sched.h
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2030,6 +2030,15 @@ static inline int spin_needbreak(spinloc
#endif
}
+static inline int rwsem_needbreak(struct rw_semaphore *sem)
+{
+#ifdef CONFIG_PREEMPT
+ return rwsem_is_contended(sem);
+#else
+ return 0;
+#endif
+}
+
/*
* Reevaluate whether the task has signals pending delivery.
* Wake the task if so.
diff --git a/lib/rwsem-spinlock.c b/lib/rwsem-spinlock.c
--- a/lib/rwsem-spinlock.c
+++ b/lib/rwsem-spinlock.c
@@ -305,6 +305,18 @@ void __downgrade_write(struct rw_semapho
spin_unlock_irqrestore(&sem->wait_lock, flags);
}
+int rwsem_is_contended(struct rw_semaphore *sem)
+{
+ /*
+ * Racy check for an empty list. False positives or negatives
+ * would be okay. False positive may cause a useless dropping of
+ * locks. False negatives may cause locks to be held a bit
+ * longer until the next check.
+ */
+ return !list_empty(&sem->wait_list);
+}
+
+EXPORT_SYMBOL(rwsem_is_contended);
EXPORT_SYMBOL(__init_rwsem);
EXPORT_SYMBOL(__down_read);
EXPORT_SYMBOL(__down_read_trylock);
diff --git a/lib/rwsem.c b/lib/rwsem.c
--- a/lib/rwsem.c
+++ b/lib/rwsem.c
@@ -251,6 +251,18 @@ asmregparm struct rw_semaphore *rwsem_do
return sem;
}
+int rwsem_is_contended(struct rw_semaphore *sem)
+{
+ /*
+ * Racy check for an empty list. False positives or negatives
+ * would be okay. False positive may cause a useless dropping of
+ * locks. False negatives may cause locks to be held a bit
+ * longer until the next check.
+ */
+ return !list_empty(&sem->wait_list);
+}
+
+EXPORT_SYMBOL(rwsem_is_contended);
EXPORT_SYMBOL(rwsem_down_read_failed);
EXPORT_SYMBOL(rwsem_down_write_failed);
EXPORT_SYMBOL(rwsem_wake);
next prev parent reply other threads:[~2008-05-07 14:40 UTC|newest]
Thread overview: 106+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-07 14:35 [PATCH 00 of 11] mmu notifier #v16 Andrea Arcangeli
2008-05-07 14:35 ` [PATCH 01 of 11] mmu-notifier-core Andrea Arcangeli
2008-05-07 17:35 ` Rik van Riel
2008-05-07 20:02 ` Andrew Morton
2008-05-07 20:05 ` Andrew Morton
2008-05-07 20:30 ` Linus Torvalds
2008-05-07 21:58 ` Andrea Arcangeli
2008-05-07 22:11 ` Linus Torvalds
2008-05-07 22:27 ` Andrea Arcangeli
2008-05-07 22:31 ` [ofa-general] " Roland Dreier
2008-05-07 22:39 ` Andrea Arcangeli
2008-05-07 23:03 ` Linus Torvalds
2008-05-07 22:37 ` Andrea Arcangeli
2008-05-07 23:38 ` Linus Torvalds
2008-05-07 23:00 ` Linus Torvalds
2008-05-07 14:35 ` [PATCH 02 of 11] get_task_mm Andrea Arcangeli
2008-05-07 15:59 ` Robin Holt
2008-05-07 16:20 ` Andrea Arcangeli
2008-05-07 14:35 ` [PATCH 03 of 11] invalidate_page outside PT lock Andrea Arcangeli
2008-05-07 17:39 ` Rik van Riel
2008-05-07 17:57 ` Andrea Arcangeli
2008-05-07 14:35 ` [PATCH 04 of 11] free-pgtables Andrea Arcangeli
2008-05-07 17:41 ` Rik van Riel
2008-05-07 14:35 ` [PATCH 05 of 11] unmap vmas tlb flushing Andrea Arcangeli
2008-05-07 17:46 ` Rik van Riel
2008-05-07 14:35 ` Andrea Arcangeli [this message]
2008-05-07 14:35 ` [PATCH 07 of 11] i_mmap_rwsem Andrea Arcangeli
2008-05-07 14:35 ` [PATCH 08 of 11] anon-vma-rwsem Andrea Arcangeli
2008-05-07 20:56 ` Linus Torvalds
2008-05-07 21:26 ` Andrea Arcangeli
2008-05-07 21:36 ` Linus Torvalds
2008-05-07 22:22 ` Andrea Arcangeli
2008-05-07 22:31 ` Andrew Morton
2008-05-07 22:44 ` Andrea Arcangeli
2008-05-07 22:59 ` Andrew Morton
2008-05-07 23:19 ` Linus Torvalds
2008-05-07 23:39 ` Christoph Lameter
2008-05-08 0:03 ` Linus Torvalds
2008-05-08 0:52 ` Robin Holt
2008-05-08 0:56 ` Christoph Lameter
2008-05-08 1:07 ` Linus Torvalds
2008-05-08 1:39 ` Linus Torvalds
2008-05-08 1:52 ` Andrea Arcangeli
2008-05-08 1:57 ` Linus Torvalds
2008-05-08 2:24 ` Andrea Arcangeli
2008-05-08 2:32 ` Linus Torvalds
2008-05-07 23:39 ` Andrea Arcangeli
2008-05-08 1:02 ` Linus Torvalds
2008-05-08 1:12 ` Christoph Lameter
2008-05-08 1:32 ` Linus Torvalds
2008-05-08 2:56 ` Andrea Arcangeli
2008-05-08 3:10 ` Christoph Lameter
2008-05-08 3:41 ` Andrea Arcangeli
2008-05-08 4:14 ` Linus Torvalds
2008-05-08 5:20 ` Andrea Arcangeli
2008-05-08 5:27 ` Pekka Enberg
2008-05-08 5:30 ` Pekka Enberg
2008-05-08 5:49 ` Andrea Arcangeli
2008-05-08 15:03 ` Linus Torvalds
2008-05-08 16:11 ` Linus Torvalds
2008-05-08 22:01 ` Andrea Arcangeli
2008-05-09 18:37 ` Peter Zijlstra
2008-05-09 18:55 ` Andrea Arcangeli
2008-05-09 19:04 ` Peter Zijlstra
2008-05-08 1:26 ` Andrea Arcangeli
2008-05-07 23:28 ` Benjamin Herrenschmidt
2008-05-07 23:45 ` Andrea Arcangeli
2008-05-08 1:34 ` Andrea Arcangeli
2008-05-13 12:14 ` Nick Piggin
2008-05-14 5:43 ` Benjamin Herrenschmidt
2008-05-14 6:06 ` Nick Piggin
2008-05-14 13:15 ` Jack Steiner
2008-05-07 22:44 ` Linus Torvalds
2008-05-07 22:58 ` Andrea Arcangeli
2008-05-07 23:02 ` Andrea Arcangeli
2008-05-07 23:09 ` Linus Torvalds
2008-05-08 0:38 ` Robin Holt
2008-05-08 0:55 ` Linus Torvalds
2008-05-13 12:06 ` Nick Piggin
2008-05-13 15:32 ` Robin Holt
2008-05-14 4:11 ` Nick Piggin
2008-05-14 11:26 ` Robin Holt
2008-05-14 15:18 ` Linus Torvalds
2008-05-14 16:22 ` Robin Holt
2008-05-14 16:56 ` Linus Torvalds
2008-05-14 17:57 ` Christoph Lameter
2008-05-14 18:27 ` Linus Torvalds
2008-05-17 1:38 ` mm notifier: Notifications when pages are unmapped Christoph Lameter
2008-05-15 7:57 ` [PATCH 08 of 11] anon-vma-rwsem Nick Piggin
2008-05-15 11:01 ` Robin Holt
2008-05-15 11:12 ` Avi Kivity
2008-05-15 17:33 ` Christoph Lameter
2008-05-15 23:52 ` Nick Piggin
2008-05-16 11:23 ` Robin Holt
2008-05-16 11:50 ` Robin Holt
2008-05-20 5:31 ` Nick Piggin
2008-05-20 10:01 ` Robin Holt
2008-05-20 10:50 ` Nick Piggin
2008-05-20 11:05 ` Robin Holt
2008-05-20 11:14 ` Nick Piggin
2008-05-20 11:26 ` Robin Holt
2008-05-07 22:42 ` Jack Steiner
2008-05-07 14:35 ` [PATCH 09 of 11] mm_lock-rwsem Andrea Arcangeli
2008-05-07 14:36 ` [PATCH 10 of 11] export zap_page_range for XPMEM Andrea Arcangeli
2008-05-07 14:36 ` [PATCH 11 of 11] mmap sems Andrea Arcangeli
-- strict thread matches above, loose matches on Subject: below --
2008-05-02 15:05 [PATCH 00 of 11] mmu notifier #v15 Andrea Arcangeli
2008-05-02 15:05 ` [PATCH 06 of 11] rwsem contended Andrea Arcangeli
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