diff options
Diffstat (limited to 'include/linux/seqlock.h')
| -rw-r--r-- | include/linux/seqlock.h | 79 |
1 files changed, 2 insertions, 77 deletions
diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h index e92f9d5577ba..d90d8ee29d81 100644 --- a/include/linux/seqlock.h +++ b/include/linux/seqlock.h @@ -18,6 +18,7 @@ #include <linux/lockdep.h> #include <linux/mutex.h> #include <linux/preempt.h> +#include <linux/seqlock_types.h> #include <linux/spinlock.h> #include <asm/processor.h> @@ -37,37 +38,6 @@ */ #define KCSAN_SEQLOCK_REGION_MAX 1000 -/* - * Sequence counters (seqcount_t) - * - * This is the raw counting mechanism, without any writer protection. - * - * Write side critical sections must be serialized and non-preemptible. - * - * If readers can be invoked from hardirq or softirq contexts, - * interrupts or bottom halves must also be respectively disabled before - * entering the write section. - * - * This mechanism can't be used if the protected data contains pointers, - * as the writer can invalidate a pointer that a reader is following. - * - * If the write serialization mechanism is one of the common kernel - * locking primitives, use a sequence counter with associated lock - * (seqcount_LOCKNAME_t) instead. - * - * If it's desired to automatically handle the sequence counter writer - * serialization and non-preemptibility requirements, use a sequential - * lock (seqlock_t) instead. - * - * See Documentation/locking/seqlock.rst - */ -typedef struct seqcount { - unsigned sequence; -#ifdef CONFIG_DEBUG_LOCK_ALLOC - struct lockdep_map dep_map; -#endif -} seqcount_t; - static inline void __seqcount_init(seqcount_t *s, const char *name, struct lock_class_key *key) { @@ -132,28 +102,6 @@ static inline void seqcount_lockdep_reader_access(const seqcount_t *s) */ /* - * For PREEMPT_RT, seqcount_LOCKNAME_t write side critical sections cannot - * disable preemption. It can lead to higher latencies, and the write side - * sections will not be able to acquire locks which become sleeping locks - * (e.g. spinlock_t). - * - * To remain preemptible while avoiding a possible livelock caused by the - * reader preempting the writer, use a different technique: let the reader - * detect if a seqcount_LOCKNAME_t writer is in progress. If that is the - * case, acquire then release the associated LOCKNAME writer serialization - * lock. This will allow any possibly-preempted writer to make progress - * until the end of its writer serialization lock critical section. - * - * This lock-unlock technique must be implemented for all of PREEMPT_RT - * sleeping locks. See Documentation/locking/locktypes.rst - */ -#if defined(CONFIG_LOCKDEP) || defined(CONFIG_PREEMPT_RT) -#define __SEQ_LOCK(expr) expr -#else -#define __SEQ_LOCK(expr) -#endif - -/* * typedef seqcount_LOCKNAME_t - sequence counter with LOCKNAME associated * @seqcount: The real sequence counter * @lock: Pointer to the associated lock @@ -194,11 +142,6 @@ static inline void seqcount_lockdep_reader_access(const seqcount_t *s) * @lockbase: prefix for associated lock/unlock */ #define SEQCOUNT_LOCKNAME(lockname, locktype, preemptible, lockbase) \ -typedef struct seqcount_##lockname { \ - seqcount_t seqcount; \ - __SEQ_LOCK(locktype *lock); \ -} seqcount_##lockname##_t; \ - \ static __always_inline seqcount_t * \ __seqprop_##lockname##_ptr(seqcount_##lockname##_t *s) \ { \ @@ -284,6 +227,7 @@ SEQCOUNT_LOCKNAME(raw_spinlock, raw_spinlock_t, false, raw_spin) SEQCOUNT_LOCKNAME(spinlock, spinlock_t, __SEQ_RT, spin) SEQCOUNT_LOCKNAME(rwlock, rwlock_t, __SEQ_RT, read) SEQCOUNT_LOCKNAME(mutex, struct mutex, true, mutex) +#undef SEQCOUNT_LOCKNAME /* * SEQCNT_LOCKNAME_ZERO - static initializer for seqcount_LOCKNAME_t @@ -794,25 +738,6 @@ static inline void raw_write_seqcount_latch(seqcount_latch_t *s) smp_wmb(); /* increment "sequence" before following stores */ } -/* - * Sequential locks (seqlock_t) - * - * Sequence counters with an embedded spinlock for writer serialization - * and non-preemptibility. - * - * For more info, see: - * - Comments on top of seqcount_t - * - Documentation/locking/seqlock.rst - */ -typedef struct { - /* - * Make sure that readers don't starve writers on PREEMPT_RT: use - * seqcount_spinlock_t instead of seqcount_t. Check __SEQ_LOCK(). - */ - seqcount_spinlock_t seqcount; - spinlock_t lock; -} seqlock_t; - #define __SEQLOCK_UNLOCKED(lockname) \ { \ .seqcount = SEQCNT_SPINLOCK_ZERO(lockname, &(lockname).lock), \ |