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From 2b53d849f243cd5f758daa7948be4c138e1571e5 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 25 Aug 2009 10:46:10 +0200
Subject: [PATCH] rt: Fix recursive read lock of rw_semaphores
commit 872fa3a2575486998d8b0380e5d6ef391d0305a8 in tip.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
kernel/rt.c | 22 ++++++++++++++++++----
1 files changed, 18 insertions(+), 4 deletions(-)
diff --git a/kernel/rt.c b/kernel/rt.c
index 7da3299..710cef5 100644
--- a/kernel/rt.c
+++ b/kernel/rt.c
@@ -303,7 +303,8 @@ EXPORT_SYMBOL(rt_up_write);
void rt_up_read(struct rw_semaphore *rwsem)
{
rwsem_release(&rwsem->dep_map, 1, _RET_IP_);
- rt_mutex_unlock(&rwsem->lock);
+ if (--rwsem->read_depth == 0)
+ rt_mutex_unlock(&rwsem->lock);
}
EXPORT_SYMBOL(rt_up_read);
@@ -314,6 +315,7 @@ EXPORT_SYMBOL(rt_up_read);
void rt_downgrade_write(struct rw_semaphore *rwsem)
{
BUG_ON(rt_mutex_real_owner(&rwsem->lock) != current);
+ rwsem->read_depth = 1;
}
EXPORT_SYMBOL(rt_downgrade_write);
@@ -343,18 +345,29 @@ EXPORT_SYMBOL(rt_down_write_nested);
int rt_down_read_trylock(struct rw_semaphore *rwsem)
{
- int ret = rt_mutex_trylock(&rwsem->lock);
+ struct rt_mutex *lock = &rwsem->lock;
+ int ret = 1;
- if (ret)
+ if (rt_mutex_real_owner(lock) != current)
+ ret = rt_mutex_trylock(&rwsem->lock);
+
+ if (ret) {
+ rwsem->read_depth++;
rwsem_acquire(&rwsem->dep_map, 0, 1, _RET_IP_);
+ }
return ret;
}
EXPORT_SYMBOL(rt_down_read_trylock);
static void __rt_down_read(struct rw_semaphore *rwsem, int subclass)
{
+ struct rt_mutex *lock = &rwsem->lock;
+
rwsem_acquire_read(&rwsem->dep_map, subclass, 0, _RET_IP_);
- rt_mutex_lock(&rwsem->lock);
+
+ if (rt_mutex_real_owner(lock) != current)
+ rt_mutex_lock(&rwsem->lock);
+ rwsem->read_depth++;
}
void rt_down_read(struct rw_semaphore *rwsem)
@@ -380,6 +393,7 @@ void __rt_rwsem_init(struct rw_semaphore *rwsem, char *name,
lockdep_init_map(&rwsem->dep_map, name, key, 0);
#endif
__rt_mutex_init(&rwsem->lock, name);
+ rwsem->read_depth = 0;
}
EXPORT_SYMBOL(__rt_rwsem_init);
--
1.7.0.4
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