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From 9ac2457a8b4a55310597414c90ce00b599c04743 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Sat, 16 Jul 2011 18:40:26 +0200
Subject: [PATCH 011/270] seqlock: Use seqcount
No point in having different implementations for the same thing.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
include/linux/seqlock.h | 174 +++++++++++++++++++++++++----------------------
1 file changed, 92 insertions(+), 82 deletions(-)
diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h
index cb0599c..1829905 100644
--- a/include/linux/seqlock.h
+++ b/include/linux/seqlock.h
@@ -30,81 +30,12 @@
#include <linux/preempt.h>
#include <asm/processor.h>
-typedef struct {
- unsigned sequence;
- spinlock_t lock;
-} seqlock_t;
-
-/*
- * These macros triggered gcc-3.x compile-time problems. We think these are
- * OK now. Be cautious.
- */
-#define __SEQLOCK_UNLOCKED(lockname) \
- { 0, __SPIN_LOCK_UNLOCKED(lockname) }
-
-#define seqlock_init(x) \
- do { \
- (x)->sequence = 0; \
- spin_lock_init(&(x)->lock); \
- } while (0)
-
-#define DEFINE_SEQLOCK(x) \
- seqlock_t x = __SEQLOCK_UNLOCKED(x)
-
-/* Lock out other writers and update the count.
- * Acts like a normal spin_lock/unlock.
- * Don't need preempt_disable() because that is in the spin_lock already.
- */
-static inline void write_seqlock(seqlock_t *sl)
-{
- spin_lock(&sl->lock);
- ++sl->sequence;
- smp_wmb();
-}
-
-static inline void write_sequnlock(seqlock_t *sl)
-{
- smp_wmb();
- sl->sequence++;
- spin_unlock(&sl->lock);
-}
-
-/* Start of read calculation -- fetch last complete writer token */
-static __always_inline unsigned read_seqbegin(const seqlock_t *sl)
-{
- unsigned ret;
-
-repeat:
- ret = ACCESS_ONCE(sl->sequence);
- if (unlikely(ret & 1)) {
- cpu_relax();
- goto repeat;
- }
- smp_rmb();
-
- return ret;
-}
-
-/*
- * Test if reader processed invalid data.
- *
- * If sequence value changed then writer changed data while in section.
- */
-static __always_inline int read_seqretry(const seqlock_t *sl, unsigned start)
-{
- smp_rmb();
-
- return unlikely(sl->sequence != start);
-}
-
-
/*
* Version using sequence counter only.
* This can be used when code has its own mutex protecting the
* updating starting before the write_seqcountbeqin() and ending
* after the write_seqcount_end().
*/
-
typedef struct seqcount {
unsigned sequence;
} seqcount_t;
@@ -207,7 +138,6 @@ static inline int __read_seqcount_retry(const seqcount_t *s, unsigned start)
static inline int read_seqcount_retry(const seqcount_t *s, unsigned start)
{
smp_rmb();
-
return __read_seqcount_retry(s, start);
}
@@ -241,21 +171,101 @@ static inline void write_seqcount_barrier(seqcount_t *s)
s->sequence+=2;
}
+typedef struct {
+ struct seqcount seqcount;
+ spinlock_t lock;
+} seqlock_t;
+
+/*
+ * These macros triggered gcc-3.x compile-time problems. We think these are
+ * OK now. Be cautious.
+ */
+#define __SEQLOCK_UNLOCKED(lockname) \
+ { \
+ .seqcount = SEQCNT_ZERO, \
+ .lock = __SPIN_LOCK_UNLOCKED(lockname) \
+ }
+
+#define seqlock_init(x) \
+ do { \
+ seqcount_init(&(x)->seqcount); \
+ spin_lock_init(&(x)->lock); \
+ } while (0)
+
+#define DEFINE_SEQLOCK(x) \
+ seqlock_t x = __SEQLOCK_UNLOCKED(x)
+
+/*
+ * Read side functions for starting and finalizing a read side section.
+ */
+static inline unsigned read_seqbegin(const seqlock_t *sl)
+{
+ return read_seqcount_begin(&sl->seqcount);
+}
+
+static inline unsigned read_seqretry(const seqlock_t *sl, unsigned start)
+{
+ return read_seqcount_retry(&sl->seqcount, start);
+}
+
/*
- * Possible sw/hw IRQ protected versions of the interfaces.
+ * Lock out other writers and update the count.
+ * Acts like a normal spin_lock/unlock.
+ * Don't need preempt_disable() because that is in the spin_lock already.
*/
+static inline void write_seqlock(seqlock_t *sl)
+{
+ spin_lock(&sl->lock);
+ write_seqcount_begin(&sl->seqcount);
+}
+
+static inline void write_sequnlock(seqlock_t *sl)
+{
+ write_seqcount_end(&sl->seqcount);
+ spin_unlock(&sl->lock);
+}
+
+static inline void write_seqlock_bh(seqlock_t *sl)
+{
+ spin_lock_bh(&sl->lock);
+ write_seqcount_begin(&sl->seqcount);
+}
+
+static inline void write_sequnlock_bh(seqlock_t *sl)
+{
+ write_seqcount_end(&sl->seqcount);
+ spin_unlock_bh(&sl->lock);
+}
+
+static inline void write_seqlock_irq(seqlock_t *sl)
+{
+ spin_lock_irq(&sl->lock);
+ write_seqcount_begin(&sl->seqcount);
+}
+
+static inline void write_sequnlock_irq(seqlock_t *sl)
+{
+ write_seqcount_end(&sl->seqcount);
+ spin_unlock_irq(&sl->lock);
+}
+
+static inline unsigned long __write_seqlock_irqsave(seqlock_t *sl)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&sl->lock, flags);
+ write_seqcount_begin(&sl->seqcount);
+ return flags;
+}
+
#define write_seqlock_irqsave(lock, flags) \
- do { local_irq_save(flags); write_seqlock(lock); } while (0)
-#define write_seqlock_irq(lock) \
- do { local_irq_disable(); write_seqlock(lock); } while (0)
-#define write_seqlock_bh(lock) \
- do { local_bh_disable(); write_seqlock(lock); } while (0)
+ do { flags = __write_seqlock_irqsave(lock); } while (0)
-#define write_sequnlock_irqrestore(lock, flags) \
- do { write_sequnlock(lock); local_irq_restore(flags); } while(0)
-#define write_sequnlock_irq(lock) \
- do { write_sequnlock(lock); local_irq_enable(); } while(0)
-#define write_sequnlock_bh(lock) \
- do { write_sequnlock(lock); local_bh_enable(); } while(0)
+static inline void
+write_sequnlock_irqrestore(seqlock_t *sl, unsigned long flags)
+{
+ write_seqcount_end(&sl->seqcount);
+ spin_unlock_irqrestore(&sl->lock, flags);
+}
#endif /* __LINUX_SEQLOCK_H */
--
1.7.10.4
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