# HG changeset patch # User Maxim Dounin # Date 1322056538 0 # Node ID 3f6040cd731ec576b93261ba490d5e8fb210db3a # Parent 39982fa694829f4ea0621fb39a9eaa6f1593f673 Added shmtx interface to forcibly unlock mutexes. It is currently used from master process on abnormal worker termination to unlock accept mutex (unlocking of accept mutex was broken in 1.0.2). It is expected to be used in the future to unlock other mutexes as well. Shared mutex code was rewritten to make this possible in a safe way, i.e. with a check if lock was actually held by the exited process. We again use pid to lock mutex, and use separate atomic variable for a count of processes waiting in sem_wait(). diff --git a/src/core/ngx_cycle.c b/src/core/ngx_cycle.c --- a/src/core/ngx_cycle.c +++ b/src/core/ngx_cycle.c @@ -952,7 +952,7 @@ ngx_init_zone_pool(ngx_cycle_t *cycle, n #endif - if (ngx_shmtx_create(&sp->mutex, (void *) &sp->lock, file) != NGX_OK) { + if (ngx_shmtx_create(&sp->mutex, &sp->lock, file) != NGX_OK) { return NGX_ERROR; } diff --git a/src/core/ngx_shmtx.c b/src/core/ngx_shmtx.c --- a/src/core/ngx_shmtx.c +++ b/src/core/ngx_shmtx.c @@ -11,10 +11,13 @@ #if (NGX_HAVE_ATOMIC_OPS) +static void ngx_shmtx_wakeup(ngx_shmtx_t *mtx); + + ngx_int_t -ngx_shmtx_create(ngx_shmtx_t *mtx, void *addr, u_char *name) +ngx_shmtx_create(ngx_shmtx_t *mtx, ngx_shmtx_sh_t *addr, u_char *name) { - mtx->lock = addr; + mtx->lock = &addr->lock; if (mtx->spin == (ngx_uint_t) -1) { return NGX_OK; @@ -24,6 +27,8 @@ ngx_shmtx_create(ngx_shmtx_t *mtx, void #if (NGX_HAVE_POSIX_SEM) + mtx->wait = &addr->wait; + if (sem_init(&mtx->sem, 1, 0) == -1) { ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, ngx_errno, "sem_init() failed"); @@ -56,12 +61,7 @@ ngx_shmtx_destory(ngx_shmtx_t *mtx) ngx_uint_t ngx_shmtx_trylock(ngx_shmtx_t *mtx) { - ngx_atomic_uint_t val; - - val = *mtx->lock; - - return ((val & 0x80000000) == 0 - && ngx_atomic_cmp_set(mtx->lock, val, val | 0x80000000)); + return (*mtx->lock == 0 && ngx_atomic_cmp_set(mtx->lock, 0, ngx_pid)); } @@ -69,17 +69,12 @@ void ngx_shmtx_lock(ngx_shmtx_t *mtx) { ngx_uint_t i, n; - ngx_atomic_uint_t val; ngx_log_debug0(NGX_LOG_DEBUG_CORE, ngx_cycle->log, 0, "shmtx lock"); for ( ;; ) { - val = *mtx->lock; - - if ((val & 0x80000000) == 0 - && ngx_atomic_cmp_set(mtx->lock, val, val | 0x80000000)) - { + if (*mtx->lock == 0 && ngx_atomic_cmp_set(mtx->lock, 0, ngx_pid)) { return; } @@ -91,10 +86,8 @@ ngx_shmtx_lock(ngx_shmtx_t *mtx) ngx_cpu_pause(); } - val = *mtx->lock; - - if ((val & 0x80000000) == 0 - && ngx_atomic_cmp_set(mtx->lock, val, val | 0x80000000)) + if (*mtx->lock == 0 + && ngx_atomic_cmp_set(mtx->lock, 0, ngx_pid)) { return; } @@ -104,24 +97,24 @@ ngx_shmtx_lock(ngx_shmtx_t *mtx) #if (NGX_HAVE_POSIX_SEM) if (mtx->semaphore) { - val = *mtx->lock; + ngx_atomic_fetch_add(mtx->wait, 1); - if ((val & 0x80000000) - && ngx_atomic_cmp_set(mtx->lock, val, val + 1)) - { - ngx_log_debug1(NGX_LOG_DEBUG_CORE, ngx_cycle->log, 0, - "shmtx wait %XA", val); + if (*mtx->lock == 0 && ngx_atomic_cmp_set(mtx->lock, 0, ngx_pid)) { + return; + } + + ngx_log_debug1(NGX_LOG_DEBUG_CORE, ngx_cycle->log, 0, + "shmtx wait %uA", *mtx->wait); - while (sem_wait(&mtx->sem) == -1) { - ngx_err_t err; + while (sem_wait(&mtx->sem) == -1) { + ngx_err_t err; - err = ngx_errno; + err = ngx_errno; - if (err != NGX_EINTR) { - ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, err, - "sem_wait() failed while waiting on shmtx"); - break; - } + if (err != NGX_EINTR) { + ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, err, + "sem_wait() failed while waiting on shmtx"); + break; } ngx_log_debug0(NGX_LOG_DEBUG_CORE, ngx_cycle->log, 0, @@ -141,31 +134,56 @@ ngx_shmtx_lock(ngx_shmtx_t *mtx) void ngx_shmtx_unlock(ngx_shmtx_t *mtx) { - ngx_atomic_uint_t val, old, wait; - if (mtx->spin != (ngx_uint_t) -1) { ngx_log_debug0(NGX_LOG_DEBUG_CORE, ngx_cycle->log, 0, "shmtx unlock"); } + if (ngx_atomic_cmp_set(mtx->lock, ngx_pid, 0)) { + ngx_shmtx_wakeup(mtx); + } +} + + +ngx_uint_t +ngx_shmtx_force_unlock(ngx_shmtx_t *mtx, ngx_pid_t pid) +{ + ngx_log_debug0(NGX_LOG_DEBUG_CORE, ngx_cycle->log, 0, + "shmtx forced unlock"); + + if (ngx_atomic_cmp_set(mtx->lock, pid, 0)) { + ngx_shmtx_wakeup(mtx); + return 1; + } + + return 0; +} + + +static void +ngx_shmtx_wakeup(ngx_shmtx_t *mtx) +{ +#if (NGX_HAVE_POSIX_SEM) + ngx_atomic_uint_t wait; + + if (!mtx->semaphore) { + return; + } + for ( ;; ) { - old = *mtx->lock; - wait = old & 0x7fffffff; - val = wait ? wait - 1 : 0; + wait = *mtx->wait; - if (ngx_atomic_cmp_set(mtx->lock, old, val)) { + if (wait == 0) { + return; + } + + if (ngx_atomic_cmp_set(mtx->wait, wait, wait - 1)) { break; } } -#if (NGX_HAVE_POSIX_SEM) - - if (wait == 0 || !mtx->semaphore) { - return; - } - ngx_log_debug1(NGX_LOG_DEBUG_CORE, ngx_cycle->log, 0, - "shmtx wake %XA", old); + "shmtx wake %uA", wait); if (sem_post(&mtx->sem) == -1) { ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, ngx_errno, @@ -180,7 +198,7 @@ ngx_shmtx_unlock(ngx_shmtx_t *mtx) ngx_int_t -ngx_shmtx_create(ngx_shmtx_t *mtx, void *addr, u_char *name) +ngx_shmtx_create(ngx_shmtx_t *mtx, ngx_shmtx_sh_t *addr, u_char *name) { if (mtx->name) { @@ -280,4 +298,11 @@ ngx_shmtx_unlock(ngx_shmtx_t *mtx) ngx_log_abort(err, ngx_unlock_fd_n " %s failed", mtx->name); } + +void +ngx_shmtx_force_unlock(ngx_shmtx_t *mtx, ngx_pid_t pid) +{ + /* void */ +} + #endif diff --git a/src/core/ngx_shmtx.h b/src/core/ngx_shmtx.h --- a/src/core/ngx_shmtx.h +++ b/src/core/ngx_shmtx.h @@ -13,9 +13,18 @@ typedef struct { + ngx_atomic_t lock; +#if (NGX_HAVE_POSIX_SEM) + ngx_atomic_t wait; +#endif +} ngx_shmtx_sh_t; + + +typedef struct { #if (NGX_HAVE_ATOMIC_OPS) ngx_atomic_t *lock; #if (NGX_HAVE_POSIX_SEM) + ngx_atomic_t *wait; ngx_uint_t semaphore; sem_t sem; #endif @@ -27,11 +36,13 @@ typedef struct { } ngx_shmtx_t; -ngx_int_t ngx_shmtx_create(ngx_shmtx_t *mtx, void *addr, u_char *name); +ngx_int_t ngx_shmtx_create(ngx_shmtx_t *mtx, ngx_shmtx_sh_t *addr, + u_char *name); void ngx_shmtx_destory(ngx_shmtx_t *mtx); ngx_uint_t ngx_shmtx_trylock(ngx_shmtx_t *mtx); void ngx_shmtx_lock(ngx_shmtx_t *mtx); void ngx_shmtx_unlock(ngx_shmtx_t *mtx); +ngx_uint_t ngx_shmtx_force_unlock(ngx_shmtx_t *mtx, ngx_pid_t pid); #endif /* _NGX_SHMTX_H_INCLUDED_ */ diff --git a/src/core/ngx_slab.h b/src/core/ngx_slab.h --- a/src/core/ngx_slab.h +++ b/src/core/ngx_slab.h @@ -22,7 +22,7 @@ struct ngx_slab_page_s { typedef struct { - ngx_atomic_t lock; + ngx_shmtx_sh_t lock; size_t min_size; size_t min_shift; diff --git a/src/event/ngx_event.c b/src/event/ngx_event.c --- a/src/event/ngx_event.c +++ b/src/event/ngx_event.c @@ -521,7 +521,8 @@ ngx_event_module_init(ngx_cycle_t *cycle ngx_accept_mutex_ptr = (ngx_atomic_t *) shared; ngx_accept_mutex.spin = (ngx_uint_t) -1; - if (ngx_shmtx_create(&ngx_accept_mutex, shared, cycle->lock_file.data) + if (ngx_shmtx_create(&ngx_accept_mutex, (ngx_shmtx_sh_t *) shared, + cycle->lock_file.data) != NGX_OK) { return NGX_ERROR; diff --git a/src/os/unix/ngx_process.c b/src/os/unix/ngx_process.c --- a/src/os/unix/ngx_process.c +++ b/src/os/unix/ngx_process.c @@ -504,7 +504,7 @@ ngx_process_get_status(void) * held it */ - ngx_atomic_cmp_set(ngx_accept_mutex_ptr, pid, 0); + ngx_shmtx_force_unlock(&ngx_accept_mutex, pid); }