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From: Oleg Nesterov <oleg@redhat.com>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <david@fromorbit.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Jan Kara <jack@suse.cz>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	Peter Zijlstra <peterz@infradead.org>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v3 4/8] percpu-rwsem: introduce percpu_down_read_trylock()
Date: Fri, 14 Aug 2015 19:19:57 +0200	[thread overview]
Message-ID: <20150814171957.GA15069@redhat.com> (raw)
In-Reply-To: <20150814171935.GA15042@redhat.com>

Add percpu_down_read_trylock(), it will have the user soon.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 include/linux/percpu-rwsem.h  |    1 +
 kernel/locking/percpu-rwsem.c |   13 +++++++++++++
 2 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h
index 3e58226..3ebf982 100644
--- a/include/linux/percpu-rwsem.h
+++ b/include/linux/percpu-rwsem.h
@@ -17,6 +17,7 @@ struct percpu_rw_semaphore {
 };
 
 extern void percpu_down_read(struct percpu_rw_semaphore *);
+extern int  percpu_down_read_trylock(struct percpu_rw_semaphore *);
 extern void percpu_up_read(struct percpu_rw_semaphore *);
 
 extern void percpu_down_write(struct percpu_rw_semaphore *);
diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c
index 2c54c64..4bc2127 100644
--- a/kernel/locking/percpu-rwsem.c
+++ b/kernel/locking/percpu-rwsem.c
@@ -73,6 +73,19 @@ void percpu_down_read(struct percpu_rw_semaphore *brw)
 	__up_read(&brw->rw_sem);
 }
 
+int percpu_down_read_trylock(struct percpu_rw_semaphore *brw)
+{
+	if (unlikely(!update_fast_ctr(brw, +1))) {
+		if (!__down_read_trylock(&brw->rw_sem))
+			return 0;
+		atomic_inc(&brw->slow_read_ctr);
+		__up_read(&brw->rw_sem);
+	}
+
+	rwsem_acquire_read(&brw->rw_sem.dep_map, 0, 1, _RET_IP_);
+	return 1;
+}
+
 void percpu_up_read(struct percpu_rw_semaphore *brw)
 {
 	rwsem_release(&brw->rw_sem.dep_map, 1, _RET_IP_);
-- 
1.5.5.1


  parent reply	other threads:[~2015-08-14 17:22 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-08-14 17:19 [PATCH v3 0/8] change sb_writers to use percpu_rw_semaphore Oleg Nesterov
2015-08-14 17:19 ` [PATCH v3 1/8] introduce __sb_writers_{acquired,release}() helpers Oleg Nesterov
2015-08-14 17:19 ` [PATCH v3 2/8] fix the broken lockdep logic in __sb_start_write() Oleg Nesterov
2015-08-14 17:19 ` [PATCH v3 3/8] document rwsem_release() in sb_wait_write() Oleg Nesterov
2015-08-14 17:19 ` Oleg Nesterov [this message]
2015-08-14 17:20 ` [PATCH v3 5/8] percpu-rwsem: introduce percpu_rwsem_release() and percpu_rwsem_acquire() Oleg Nesterov
2015-08-14 17:20 ` [PATCH v3 6/8] percpu-rwsem: kill CONFIG_PERCPU_RWSEM Oleg Nesterov
2015-08-14 17:20 ` [PATCH v3 7/8] shift percpu_counter_destroy() into destroy_super_work() Oleg Nesterov
2015-08-14 17:20 ` [PATCH v3 8/8] change sb_writers to use percpu_rw_semaphore Oleg Nesterov
2015-08-15  7:17 ` [PATCH v3 0/8] " Al Viro
2015-08-15 12:03   ` Oleg Nesterov
2015-08-16 13:47 ` Arthur Marsh
2015-08-17 11:35   ` Oleg Nesterov

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