[PATCH 2 of 2] Unlock of shared memory zones on process crash

[Maxim Dounin]

# HG changeset patch
# User Maxim Dounin <mdounin at mdounin.ru>
# Date 1321579276 -10800
# Node ID e32c7ec2800b43ad5fe4bf98bc69fda4abdadf39
# Parent  98907592714e29982979010e310cd482d414b53f
Unlock of shared memory zones on process crash.

If process exited abnormally while holding lock on some shared memory zone -
unlock it.  It may be not safe thing to do (as crash with lock held may
result in corrupted shared memory structure, and other processes will
subsequently crash while trying to access shared data), therefore complain
loudly if unlock succeeds.

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
@@ -445,12 +445,15 @@ ngx_signal_handler(int signo)
 static void
 ngx_process_get_status(void)
 {
-    int              status;
-    char            *process;
-    ngx_pid_t        pid;
-    ngx_err_t        err;
-    ngx_int_t        i;
-    ngx_uint_t       one;
+    int               status;
+    char             *process;
+    ngx_pid_t         pid;
+    ngx_err_t         err;
+    ngx_int_t         i;
+    ngx_uint_t        n, one;
+    ngx_shm_zone_t   *shm_zone;
+    ngx_list_part_t  *part;
+    ngx_slab_pool_t  *sp;
 
     one = 0;
 
@@ -497,17 +500,6 @@ ngx_process_get_status(void)
         }
 
 
-        if (ngx_accept_mutex_ptr) {
-
-            /*
-             * unlock the accept mutex if the abnormally exited process
-             * held it
-             */
-
-            ngx_shmtx_force_unlock(&ngx_accept_mutex, pid);
-        }
-
-
         one = 1;
         process = "unknown process";
 
@@ -545,6 +537,46 @@ ngx_process_get_status(void)
                           process, pid, WEXITSTATUS(status));
             ngx_processes[i].respawn = 0;
         }
+
+
+        if (ngx_accept_mutex_ptr) {
+
+            /*
+             * unlock the accept mutex if the abnormally exited process
+             * held it
+             */
+
+            ngx_shmtx_force_unlock(&ngx_accept_mutex, pid);
+        }
+
+
+        /*
+         * unlock shared memory mutexes if held by the abnormally exited
+         * process
+         */
+
+        part = (ngx_list_part_t *) &ngx_cycle->shared_memory.part;
+        shm_zone = part->elts;
+
+        for (n = 0; /* void */ ; n++) {
+
+            if (n >= part->nelts) {
+                if (part->next == NULL) {
+                    break;
+                }
+                part = part->next;
+                shm_zone = part->elts;
+                n = 0;
+            }
+
+            sp = (ngx_slab_pool_t *) shm_zone[n].shm.addr;
+
+            if (ngx_shmtx_force_unlock(&sp->mutex, pid)) {
+                ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, 0,
+                              "shared memory zone \"%V\" was locked by %P",
+                              &shm_zone[n].shm.name, pid);
+            }
+        }
     }
 }