#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);
-}
-
-static inline int write_tryseqlock(seqlock_t *sl)
-{
- int ret = spin_trylock(&sl->lock);
-
- if (ret) {
- ++sl->sequence;
- smp_wmb();
- }
- return ret;
-}
-
-/* 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;
unsigned ret;
repeat:
- ret = s->sequence;
+ ret = ACCESS_ONCE(s->sequence);
if (unlikely(ret & 1)) {
cpu_relax();
goto repeat;
return ret;
}
+/**
+ * raw_seqcount_begin - begin a seq-read critical section
+ * @s: pointer to seqcount_t
+ * Returns: count to be passed to read_seqcount_retry
+ *
+ * raw_seqcount_begin opens a read critical section of the given seqcount.
+ * Validity of the critical section is tested by checking read_seqcount_retry
+ * function.
+ *
+ * Unlike read_seqcount_begin(), this function will not wait for the count
+ * to stabilize. If a writer is active when we begin, we will fail the
+ * read_seqcount_retry() instead of stabilizing at the beginning of the
+ * critical section.
+ */
+static inline unsigned raw_seqcount_begin(const seqcount_t *s)
+{
+ unsigned ret = ACCESS_ONCE(s->sequence);
+ smp_rmb();
+ return ret & ~1;
+}
+
/**
* __read_seqcount_retry - end a seq-read critical section (without barrier)
* @s: pointer to seqcount_t
static inline int read_seqcount_retry(const seqcount_t *s, unsigned start)
{
smp_rmb();
-
return __read_seqcount_retry(s, start);
}
s->sequence+=2;
}
+typedef struct {
+ struct seqcount seqcount;
+ spinlock_t lock;
+} seqlock_t;
+
/*
- * Possible sw/hw IRQ protected versions of the interfaces.
+ * These macros triggered gcc-3.x compile-time problems. We think these are
+ * OK now. Be cautious.
*/
-#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)
+#define __SEQLOCK_UNLOCKED(lockname) \
+ { \
+ .seqcount = SEQCNT_ZERO, \
+ .lock = __SPIN_LOCK_UNLOCKED(lockname) \
+ }
-#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)
+#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);
+}
-#define read_seqbegin_irqsave(lock, flags) \
- ({ local_irq_save(flags); read_seqbegin(lock); })
+static inline unsigned read_seqretry(const seqlock_t *sl, unsigned start)
+{
+ return read_seqcount_retry(&sl->seqcount, start);
+}
-#define read_seqretry_irqrestore(lock, iv, flags) \
- ({ \
- int ret = read_seqretry(lock, iv); \
- local_irq_restore(flags); \
- ret; \
- })
+/*
+ * 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 { flags = __write_seqlock_irqsave(lock); } 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 */
projects / firefly-linux-kernel-4.4.55.git / blobdiff