use POSIX semaphores in shmtx instead of sched_yield()

number of spinlock spins are increased twice

1 files changed, 215 insertions, 0 deletions

diff --git a/src/core/ngx_shmtx.c b/src/core/ngx_shmtx.c
index ead94e484..3b429c4f9 100644
--- a/src/core/ngx_shmtx.c
+++ b/src/core/ngx_shmtx.c
@@ -16,9 +16,166 @@ ngx_shmtx_create(ngx_shmtx_t *mtx, void *addr, u_char *name)
 {
     mtx->lock = addr;
 
+    if (mtx->spin == (ngx_uint_t) -1) {
+        return NGX_OK;
+    }
+
+    mtx->spin = 2048;
+
+#if (NGX_HAVE_POSIX_SEM)
+
+    if (sem_init(&mtx->sem, 1, 0) == -1) {
+        ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, ngx_errno,
+                      "sem_init() failed");
+    } else {
+        mtx->semaphore = 1;
+    }
+
+#endif
+
     return NGX_OK;
 }
 
+
+void
+ngx_shmtx_destory(ngx_shmtx_t *mtx)
+{
+#if (NGX_HAVE_POSIX_SEM)
+
+    if (mtx->semaphore) {
+        if (sem_destroy(&mtx->sem) == -1) {
+            ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, ngx_errno,
+                          "sem_destroy() failed");
+        }
+    }
+
+#endif
+}
+
+
+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));
+}
+
+
+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))
+        {
+            return;
+        }
+
+        if (ngx_ncpu > 1) {
+
+            for (n = 1; n < mtx->spin; n <<= 1) {
+
+                for (i = 0; i < n; i++) {
+                    ngx_cpu_pause();
+                }
+
+                val = *mtx->lock;
+
+                if ((val & 0x80000000) == 0
+                    && ngx_atomic_cmp_set(mtx->lock, val, val | 0x80000000))
+                {
+                    return;
+                }
+            }
+        }
+
+#if (NGX_HAVE_POSIX_SEM)
+
+        if (mtx->semaphore) {
+            val = *mtx->lock;
+
+            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);
+
+                while (sem_wait(&mtx->sem) == -1) {
+                    ngx_err_t  err;
+
+                    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;
+                    }
+                }
+
+                ngx_log_debug0(NGX_LOG_DEBUG_CORE, ngx_cycle->log, 0,
+                               "shmtx awoke");
+            }
+
+            continue;
+        }
+
+#endif
+
+        ngx_sched_yield();
+    }
+}
+
+
+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");
+    }
+
+    for ( ;; ) {
+
+        old = *mtx->lock;
+        wait = old & 0x7fffffff;
+        val = wait ? wait - 1 : 0;
+
+        if (ngx_atomic_cmp_set(mtx->lock, old, val)) {
+            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);
+
+    if (sem_post(&mtx->sem) == -1) {
+        ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, ngx_errno,
+                      "sem_post() failed while wake shmtx");
+    }
+
+#endif
+}
+
+
 #else
 
 
@@ -65,4 +222,62 @@ ngx_shmtx_destory(ngx_shmtx_t *mtx)
 }
 
 
+ngx_uint_t
+ngx_shmtx_trylock(ngx_shmtx_t *mtx)
+{
+    ngx_err_t  err;
+
+    err = ngx_trylock_fd(mtx->fd);
+
+    if (err == 0) {
+        return 1;
+    }
+
+    if (err == NGX_EAGAIN) {
+        return 0;
+    }
+
+#if __osf__ /* Tru64 UNIX */
+
+    if (err == NGX_EACCESS) {
+        return 0;
+    }
+
+#endif
+
+    ngx_log_abort(err, ngx_trylock_fd_n " %s failed", mtx->name);
+
+    return 0;
+}
+
+
+void
+ngx_shmtx_lock(ngx_shmtx_t *mtx)
+{
+    ngx_err_t  err;
+
+    err = ngx_lock_fd(mtx->fd);
+
+    if (err == 0) {
+        return;
+    }
+
+    ngx_log_abort(err, ngx_lock_fd_n " %s failed", mtx->name);
+}
+
+
+void
+ngx_shmtx_unlock(ngx_shmtx_t *mtx)
+{
+    ngx_err_t  err;
+
+    err = ngx_unlock_fd(mtx->fd);
+
+    if (err == 0) {
+        return;
+    }
+
+    ngx_log_abort(err, ngx_unlock_fd_n " %s failed", mtx->name);
+}
+
 #endif