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Date: Wed, 9 May 2007 14:11:54 +0530
From: Sripathi Kodi <sripathik@...ibm.com>
To: linux-kernel@...r.kernel.org
Cc: akpm@...l.org
Subject: [PATCH 1/2] Introduce write_trylock_irqsave
Hi,
I am trying to fix the BUG I mentioned here:
http://lkml.org/lkml/2007/04/20/41. I noticed that an elegant way to solve
this problem is to have a write_trylock_irqsave helper function. Since we
don't have this now, the code in ptrace_attach implements it using
local_irq_disable and write_trylock. I wish to add write_trylock_irqsave to
mainline kernel and then fix the -rt specific problem using this.
The patch below adds write_trylock_irqsave function.
Signed-off-by: Sripathi Kodi <sripathik@...ibm.com>
---
include/linux/spinlock.h | 2 ++
include/linux/spinlock_api_smp.h | 1 +
include/linux/spinlock_api_up.h | 2 ++
kernel/spinlock.c | 14 ++++++++++++++
4 files changed, 19 insertions(+)
Index: linux-2.6.21/include/linux/spinlock.h
===================================================================
--- linux-2.6.21.orig/include/linux/spinlock.h
+++ linux-2.6.21/include/linux/spinlock.h
@@ -171,6 +171,8 @@ do { \
#define spin_trylock(lock) __cond_lock(lock, _spin_trylock(lock))
#define read_trylock(lock) __cond_lock(lock, _read_trylock(lock))
#define write_trylock(lock) __cond_lock(lock, _write_trylock(lock))
+#define write_trylock_irqsave(lock, flags) \
+ __cond_lock(lock, _write_trylock_irqsave(lock, flags))
#define spin_lock(lock) _spin_lock(lock)
Index: linux-2.6.21/include/linux/spinlock_api_smp.h
===================================================================
--- linux-2.6.21.orig/include/linux/spinlock_api_smp.h
+++ linux-2.6.21/include/linux/spinlock_api_smp.h
@@ -41,6 +41,7 @@ unsigned long __lockfunc _write_lock_irq
int __lockfunc _spin_trylock(spinlock_t *lock);
int __lockfunc _read_trylock(rwlock_t *lock);
int __lockfunc _write_trylock(rwlock_t *lock);
+int __lockfunc _write_trylock_irqsave(rwlock_t *lock, unsigned long flags);
int __lockfunc _spin_trylock_bh(spinlock_t *lock);
void __lockfunc _spin_unlock(spinlock_t *lock) __releases(lock);
void __lockfunc _read_unlock(rwlock_t *lock) __releases(lock);
Index: linux-2.6.21/include/linux/spinlock_api_up.h
===================================================================
--- linux-2.6.21.orig/include/linux/spinlock_api_up.h
+++ linux-2.6.21/include/linux/spinlock_api_up.h
@@ -64,6 +64,8 @@
#define _spin_trylock(lock) ({ __LOCK(lock); 1; })
#define _read_trylock(lock) ({ __LOCK(lock); 1; })
#define _write_trylock(lock) ({ __LOCK(lock); 1; })
+#define _write_trylock_irqsave(lock, flags) \
+ ({ __LOCK_IRQSAVE(lock, flags); 1; })
#define _spin_trylock_bh(lock) ({ __LOCK_BH(lock); 1; })
#define _spin_unlock(lock) __UNLOCK(lock)
#define _read_unlock(lock) __UNLOCK(lock)
Index: linux-2.6.21/kernel/spinlock.c
===================================================================
--- linux-2.6.21.orig/kernel/spinlock.c
+++ linux-2.6.21/kernel/spinlock.c
@@ -60,6 +60,20 @@ int __lockfunc _write_trylock(rwlock_t *
}
EXPORT_SYMBOL(_write_trylock);
+int __lockfunc _write_trylock_irqsave(rwlock_t *lock, unsigned long flags)
+{
+ int ret;
+
+ local_irq_save(flags);
+ ret = _write_trylock(lock);
+ if (ret)
+ return ret;
+
+ local_irq_restore(flags);
+ return 0;
+}
+EXPORT_SYMBOL(_write_trylock_irqsave);
+
/*
* If lockdep is enabled then we use the non-preemption spin-ops
* even on CONFIG_PREEMPT, because lockdep assumes that interrupts are
-
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