From 2b53d849f243cd5f758daa7948be4c138e1571e5 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner 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 Signed-off-by: Paul Gortmaker --- 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