linux-kernel - [PATCH 2/4] percpu-rwsem: introduce percpu_rwsem_release() and percpu_rwsem

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Message-ID: <20150722211535.GA20007@redhat.com>
Date:	Wed, 22 Jul 2015 23:15:35 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Al Viro <viro@...iv.linux.org.uk>,
	Dave Chinner <david@...morbit.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Jan Kara <jack@...e.cz>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/4] percpu-rwsem: introduce percpu_rwsem_release() and
	percpu_rwsem_acquire()

Add percpu_rwsem_release() and percpu_rwsem_acquire() for the users
which need to return to userspace with percpu-rwsem lock held and/or
pass the ownership to another thread.

TODO: change percpu_rwsem_release() to use rwsem_clear_owner(). We can
either fold kernel/locking/rwsem.h into include/linux/rwsem.h, or add
the non-inline percpu_rwsem_clear_owner().

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 include/linux/percpu-rwsem.h |   19 +++++++++++++++++++
 1 files changed, 19 insertions(+), 0 deletions(-)

diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h
index 3ebf982..06af654 100644
--- a/include/linux/percpu-rwsem.h
+++ b/include/linux/percpu-rwsem.h
@@ -33,4 +33,23 @@ extern void percpu_free_rwsem(struct percpu_rw_semaphore *);
 	__percpu_init_rwsem(brw, #brw, &rwsem_key);		\
 })
 
+
+#define percpu_rwsem_is_held(sem) lockdep_is_held(&(sem)->rw_sem)
+
+static inline void percpu_rwsem_release(struct percpu_rw_semaphore *sem,
+					bool read, unsigned long ip)
+{
+	lock_release(&sem->rw_sem.dep_map, 1, ip);
+#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
+	if (!read)
+		sem->rw_sem.owner = NULL;
+#endif
+}
+
+static inline void percpu_rwsem_acquire(struct percpu_rw_semaphore *sem,
+					bool read, unsigned long ip)
+{
+	lock_acquire(&sem->rw_sem.dep_map, 0, 1, read, 1, NULL, ip);
+}
+
 #endif
-- 
1.5.5.1

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