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Date: Tue, 25 Sep 2007 11:29:51 -0400 (EDT)
From: Steven Rostedt <rostedt@...dmis.org>
To: Peter Zijlstra <peterz@...radead.org>
cc: LKML <linux-kernel@...r.kernel.org>,
linux-rt-users <linux-rt-users@...r.kernel.org>,
mingo@...dmis.org, Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH RT] Don't let -rt rw_semaphors do _non_owner locks
--
On Tue, 25 Sep 2007, Peter Zijlstra wrote:
> How about teaching {up,down}_read_non_owner() to barf on rw_semaphore
> in -rt?
>
Sure thing!
This patch prevents rw_semaphore in PREEMPT_RT from performing
down_read_non_owner and up_read_non_owner. If this must be used, then
either convert to a completion or use compat_rw_semaphore.
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
Index: linux-2.6.23-rc4-rt1/include/linux/rt_lock.h
===================================================================
--- linux-2.6.23-rc4-rt1.orig/include/linux/rt_lock.h 2007-09-25 09:38:56.000000000 -0400
+++ linux-2.6.23-rc4-rt1/include/linux/rt_lock.h 2007-09-25 09:42:19.000000000 -0400
@@ -248,25 +248,20 @@ do { \
__rt_rwsem_init((sem), #sem, &__key); \
} while (0)
+extern void __dont_do_this_in_rt(struct rw_semaphore *rwsem);
+
+#define rt_down_read_non_owner(rwsem) __dont_do_this_in_rt(rwsem)
+#define rt_up_read_non_owner(rwsem) __dont_do_this_in_rt(rwsem)
+
extern void fastcall rt_down_write(struct rw_semaphore *rwsem);
extern void fastcall
rt_down_read_nested(struct rw_semaphore *rwsem, int subclass);
extern void fastcall
rt_down_write_nested(struct rw_semaphore *rwsem, int subclass);
extern void fastcall rt_down_read(struct rw_semaphore *rwsem);
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
-extern void fastcall rt_down_read_non_owner(struct rw_semaphore *rwsem);
-#else
-# define rt_down_read_non_owner(rwsem) rt_down_read(rwsem)
-#endif
extern int fastcall rt_down_write_trylock(struct rw_semaphore *rwsem);
extern int fastcall rt_down_read_trylock(struct rw_semaphore *rwsem);
extern void fastcall rt_up_read(struct rw_semaphore *rwsem);
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
-extern void fastcall rt_up_read_non_owner(struct rw_semaphore *rwsem);
-#else
-# define rt_up_read_non_owner(rwsem) rt_up_read(rwsem)
-#endif
extern void fastcall rt_up_write(struct rw_semaphore *rwsem);
extern void fastcall rt_downgrade_write(struct rw_semaphore *rwsem);
Index: linux-2.6.23-rc4-rt1/kernel/rt.c
===================================================================
--- linux-2.6.23-rc4-rt1.orig/kernel/rt.c 2007-09-25 09:38:56.000000000 -0400
+++ linux-2.6.23-rc4-rt1/kernel/rt.c 2007-09-25 09:41:50.000000000 -0400
@@ -324,25 +324,6 @@ void fastcall rt_up_read(struct rw_semap
}
EXPORT_SYMBOL(rt_up_read);
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
-void fastcall rt_up_read_non_owner(struct rw_semaphore *rwsem)
-{
- unsigned long flags;
- /*
- * Read locks within the self-held write lock succeed.
- */
- spin_lock_irqsave(&rwsem->lock.wait_lock, flags);
- if (rt_mutex_real_owner(&rwsem->lock) == current && rwsem->read_depth) {
- spin_unlock_irqrestore(&rwsem->lock.wait_lock, flags);
- rwsem->read_depth--;
- return;
- }
- spin_unlock_irqrestore(&rwsem->lock.wait_lock, flags);
- rt_mutex_unlock(&rwsem->lock);
-}
-EXPORT_SYMBOL(rt_up_read_non_owner);
-#endif
-
/*
* downgrade a write lock into a read lock
* - just wake up any readers at the front of the queue
@@ -433,32 +414,6 @@ void fastcall rt_down_read_nested(struct
}
EXPORT_SYMBOL(rt_down_read_nested);
-
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
-
-/*
- * Same as rt_down_read() but no lockdep calls:
- */
-void fastcall rt_down_read_non_owner(struct rw_semaphore *rwsem)
-{
- unsigned long flags;
- /*
- * Read locks within the write lock succeed.
- */
- spin_lock_irqsave(&rwsem->lock.wait_lock, flags);
-
- if (rt_mutex_real_owner(&rwsem->lock) == current) {
- spin_unlock_irqrestore(&rwsem->lock.wait_lock, flags);
- rwsem->read_depth++;
- return;
- }
- spin_unlock_irqrestore(&rwsem->lock.wait_lock, flags);
- rt_mutex_lock(&rwsem->lock);
-}
-EXPORT_SYMBOL(rt_down_read_non_owner);
-
-#endif
-
void fastcall __rt_rwsem_init(struct rw_semaphore *rwsem, char *name,
struct lock_class_key *key)
{
-
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