[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 1322049622 -10800
# Node ID 8b41c4af392f85aa8d412989c2f766f986d9de8b
# Parent  7bedc6b7d2f34da90c6f564b7e6118c584cd826e
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
@@ -22,6 +22,7 @@ typedef struct {
 static void ngx_execute_proc(ngx_cycle_t *cycle, void *data);
 static void ngx_signal_handler(int signo);
 static void ngx_process_get_status(void);
+static void ngx_unlock_mutexes(ngx_pid_t pid);
 
 
 int              ngx_argc;
@@ -497,17 +498,6 @@ 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 +535,55 @@ ngx_process_get_status(void)
                           process, pid, WEXITSTATUS(status));
             ngx_processes[i].respawn = 0;
         }
+
+        ngx_unlock_mutexes(pid);
+    }
+}
+
+
+static void
+ngx_unlock_mutexes(ngx_pid_t pid)
+{ 
+    ngx_uint_t        i;
+    ngx_shm_zone_t   *shm_zone;
+    ngx_list_part_t  *part;
+    ngx_slab_pool_t  *sp;
+
+    /*
+     * unlock the accept mutex if the abnormally exited process
+     * held it
+     */
+
+    if (ngx_accept_mutex_ptr) {
+        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 (i = 0; /* void */ ; i++) {
+
+        if (i >= part->nelts) {
+            if (part->next == NULL) {
+                break;
+            }
+            part = part->next;
+            shm_zone = part->elts;
+            i = 0;
+        }
+
+        sp = (ngx_slab_pool_t *) shm_zone[i].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[i].shm.name, pid);
+        }
     }
 }