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().

1 files changed, 12 insertions, 1 deletions

diff --git a/src/core/ngx_shmtx.h b/src/core/ngx_shmtx.h
index 714f73aa6..3ee7d3a79 100644
--- 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_ */