Mercurial > hg > nginx-quic
diff src/core/ngx_rwlock.c @ 6101:682d8222c6b1
Core: read/write locks.
author | Ruslan Ermilov <ru@nginx.com> |
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date | Sat, 21 Mar 2015 14:05:08 +0300 |
parents | |
children | 79ddb0bdb273 |
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new file mode 100644 --- /dev/null +++ b/src/core/ngx_rwlock.c @@ -0,0 +1,112 @@ + +/* + * Copyright (C) Ruslan Ermilov + * Copyright (C) Nginx, Inc. + */ + + +#include <ngx_config.h> +#include <ngx_core.h> + + +#if (NGX_HAVE_ATOMIC_OPS) + + +#define NGX_RWLOCK_SPIN 2048 +#define NGX_RWLOCK_WLOCK ((ngx_atomic_uint_t) -1) + + +void +ngx_rwlock_wlock(ngx_atomic_t *lock) +{ + ngx_uint_t i, n; + + for ( ;; ) { + + if (*lock == 0 && ngx_atomic_cmp_set(lock, 0, NGX_RWLOCK_WLOCK)) { + return; + } + + if (ngx_ncpu > 1) { + + for (n = 1; n < NGX_RWLOCK_SPIN; n <<= 1) { + + for (i = 0; i < n; i++) { + ngx_cpu_pause(); + } + + if (*lock == 0 + && ngx_atomic_cmp_set(lock, 0, NGX_RWLOCK_WLOCK)) + { + return; + } + } + } + + ngx_sched_yield(); + } +} + + +void +ngx_rwlock_rlock(ngx_atomic_t *lock) +{ + ngx_uint_t i, n; + ngx_atomic_uint_t readers; + + for ( ;; ) { + readers = *lock; + + if (readers != NGX_RWLOCK_WLOCK + && ngx_atomic_cmp_set(lock, readers, readers + 1)) + { + return; + } + + if (ngx_ncpu > 1) { + + for (n = 1; n < NGX_RWLOCK_SPIN; n <<= 1) { + + for (i = 0; i < n; i++) { + ngx_cpu_pause(); + } + + readers = *lock; + + if (readers != NGX_RWLOCK_WLOCK + && ngx_atomic_cmp_set(lock, readers, readers + 1)) + { + return; + } + } + } + + ngx_sched_yield(); + } +} + + +void +ngx_rwlock_unlock(ngx_atomic_t *lock) +{ + ngx_atomic_uint_t readers; + + readers = *lock; + + if (readers == NGX_RWLOCK_WLOCK) { + *lock = 0; + return; + } + + for ( ;; ) { + + if (ngx_atomic_cmp_set(lock, readers, readers - 1)) { + return; + } + + readers = *lock; + } +} + + +#endif