From: Liu Tao <liutao@safe-mail.net>
To: lkml <linux-kernel@vger.kernel.org>
Subject: [patch] Add a writer prior lock methord for rwlock
Date: Wed, 04 Aug 2004 17:09:03 +0800 [thread overview]
Message-ID: <4110A7AF.2060903@safe-mail.net> (raw)
The patch adds the write_forcelock() methord, which has higher priority than
read_lock() and write_lock(). The original read_lock() and write_lock()
is not
touched, and the unlock methord is still write_unlock();
The patch gives implemention on i386, for kernel 2.6.7.
Regards
-----------------------
diff -Naur linux-2.6.7/include/asm-i386/rwlock.h
linux-2.6.7-dev/include/asm-i386/rwlock.h
--- linux-2.6.7/include/asm-i386/rwlock.h 2004-06-16
13:20:04.000000000 +0800
+++ linux-2.6.7-dev/include/asm-i386/rwlock.h 2004-08-03
09:15:02.000000000 +0800
@@ -80,4 +80,37 @@
__build_write_lock_ptr(rw, helper); \
} while (0)
+#define __build_write_forcelock_ptr(rw) \
+ asm volatile(LOCK "subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \
+ "jnz 2f\n" \
+ "1:\n" \
+ LOCK_SECTION_START("") \
+ "2:\t" \
+ "rep;nop\n\t" \
+ "cmpl $0,(%0)\n\t" \
+ "jnz 2b\n\t" \
+ "jmp 1b\n" \
+ LOCK_SECTION_END \
+ ::"a" (rw) : "memory")
+
+#define __build_write_forcelock_const(rw) \
+ asm volatile(LOCK "subl $" RW_LOCK_BIAS_STR ",%0\n\t" \
+ "jnz 2f\n" \
+ "1:\n" \
+ LOCK_SECTION_START("") \
+ "2:\t" \
+ "rep;nop\n\t" \
+ "cmpl $0,%0\n\t" \
+ "jnz 2b\n\t" \
+ "jmp 1b\n" \
+ LOCK_SECTION_END \
+ :"=m" (*(volatile int *)rw) : : "memory")
+
+#define __build_write_forcelock(rw) do { \
+ if (__builtin_constant_p(rw)) \
+ __build_write_forcelock_const(rw); \
+ else \
+ __build_write_forcelock_ptr(rw); \
+ } while (0)
+
#endif
diff -Naur linux-2.6.7/include/asm-i386/spinlock.h
linux-2.6.7-dev/include/asm-i386/spinlock.h
--- linux-2.6.7/include/asm-i386/spinlock.h 2004-06-16
13:19:02.000000000 +0800
+++ linux-2.6.7-dev/include/asm-i386/spinlock.h 2004-08-02
16:42:26.000000000 +0800
@@ -139,11 +139,13 @@
*/
typedef struct {
volatile unsigned int lock;
+ spinlock_t forcelock;
#ifdef CONFIG_DEBUG_SPINLOCK
unsigned magic;
#endif
} rwlock_t;
+#define RWLOCK_FORCELOCK , {1 SPINLOCK_MAGIC_INIT}
#define RWLOCK_MAGIC 0xdeaf1eed
#ifdef CONFIG_DEBUG_SPINLOCK
@@ -152,7 +154,7 @@
#define RWLOCK_MAGIC_INIT /* */
#endif
-#define RW_LOCK_UNLOCKED (rwlock_t) { RW_LOCK_BIAS RWLOCK_MAGIC_INIT }
+#define RW_LOCK_UNLOCKED (rwlock_t) { RW_LOCK_BIAS RWLOCK_FORCELOCK
RWLOCK_MAGIC_INIT }
#define rwlock_init(x) do { *(x) = RW_LOCK_UNLOCKED; } while(0)
@@ -185,6 +187,16 @@
__build_write_lock(rw, "__write_lock_failed");
}
+static inline void _raw_write_forcelock(rwlock_t *rw)
+{
+#ifdef CONFIG_DEBUG_SPINLOCK
+ BUG_ON(rw->magic != RWLOCK_MAGIC);
+#endif
+ _raw_spin_lock(&rw->forcelock);
+ __build_write_forcelock(rw);
+ _raw_spin_unlock(&rw->forcelock);
+}
+
#define _raw_read_unlock(rw) asm volatile("lock ; incl %0" :"=m"
((rw)->lock) : : "memory")
#define _raw_write_unlock(rw) asm volatile("lock ; addl $"
RW_LOCK_BIAS_STR ",%0":"=m" ((rw)->lock) : : "memory")
diff -Naur linux-2.6.7/include/linux/spinlock.h
linux-2.6.7-dev/include/linux/spinlock.h
--- linux-2.6.7/include/linux/spinlock.h 2004-06-16
13:19:23.000000000 +0800
+++ linux-2.6.7-dev/include/linux/spinlock.h 2004-08-04
16:25:37.000000000 +0800
@@ -231,6 +231,12 @@
} while(0)
#endif
+#define write_forcelock(lock) \
+do { \
+ preempt_disable(); \
+ _raw_write_forcelock(lock); \
+} while (0)
+
#define read_lock(lock) \
do { \
preempt_disable(); \
@@ -318,6 +324,27 @@
_raw_write_lock(lock); \
} while (0)
+#define write_forcelock_irqsave(lock, flags) \
+do { \
+ local_irq_save(flags); \
+ preempt_disable(); \
+ _raw_write_forcelock(lock); \
+} while (0)
+
+#define write_forcelock_irq(lock) \
+do { \
+ local_irq_disable(); \
+ preempt_disable(); \
+ _raw_write_forcelock(lock); \
+} while (0)
+
+#define write_forcelock_bh(lock) \
+do { \
+ local_bh_disable(); \
+ preempt_disable(); \
+ _raw_write_forcelock(lock); \
+} while (0)
+
#define spin_unlock_irqrestore(lock, flags) \
do { \
_raw_spin_unlock(lock); \
next reply other threads:[~2004-08-04 9:09 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-08-04 9:09 Liu Tao [this message]
2004-08-04 9:16 ` [patch] Add a writer prior lock methord for rwlock Arjan van de Ven
2004-08-04 10:29 ` Liu Tao
2004-08-04 10:33 ` William Lee Irwin III
2004-08-04 11:30 ` Liu Tao
2004-08-04 12:14 ` Rik van Riel
2004-08-04 9:45 ` Oliver Neukum
2004-08-04 10:30 ` Liu Tao
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