Squid-2.2.DEVEL3: Handle overloaded async-io more gracefully
    Make overloaded async-io a non-fatal error (block instead of terminate),
    and take some extra actions to limit the risk of overloading.

Index: squid/src/aiops.c
diff -u squid/src/aiops.c:1.1.1.14 squid/src/aiops.c:1.1.1.14.4.1
--- squid/src/aiops.c:1.1.1.14	Sun Jan 24 09:34:03 1999
+++ squid/src/aiops.c	Thu Mar 18 01:15:26 1999
@@ -110,6 +110,7 @@
 int aio_unlink(const char *, aio_result_t *);
 int aio_opendir(const char *, aio_result_t *);
 aio_result_t *aio_poll_done();
+int aio_sync(void);
 
 static void aio_init(void);
 static void aio_queue_request(aio_request_t *);
@@ -386,8 +387,9 @@
     }
     if (request_queue_len > RIDICULOUS_LENGTH) {
 	debug(43, 0) ("aio_queue_request: Async request queue growing uncontrollably!\n");
-	debug(43, 0) ("aio_queue_request: Possible infinite loop somewhere in squid. Restarting...\n");
-	abort();
+	debug(43, 0) ("aio_queue_request: Syncing pending I/O operations.. (blocking)\n");
+	aio_sync();
+	debug(43, 0) ("aio_queue_request: Synced\n");
     }
 }				/* aio_queue_request */
 
@@ -838,11 +840,30 @@
 int
 aio_operations_pending(void)
 {
-    if (request_done_head)
-	return 1;
-    if (busy_threads_head)
+    return request_queue_len + (request_done_head != NULL) + (busy_threads_head != NULL);
+}
+
+int
+aio_overloaded(void)
+{
+    static time_t last_warn = 0;
+    if (aio_operations_pending() > RIDICULOUS_LENGTH / 4) {
+	if (squid_curtime >= (last_warn + 15)) {
+	    debug(43, 0) ("Warning: Async-IO overloaded\n");
+	    last_warn = squid_curtime;
+	}
 	return 1;
+    }
     return 0;
+}
+
+int
+aio_sync(void)
+{
+    do {
+	aio_poll_threads();
+    } while(request_queue_len > 0);
+    return aio_operations_pending();
 }
 
 static void
Index: squid/src/async_io.c
diff -u squid/src/async_io.c:1.1.1.9 squid/src/async_io.c:1.1.1.9.2.1
--- squid/src/async_io.c:1.1.1.9	Sun Feb 14 23:29:51 1999
+++ squid/src/async_io.c	Thu Mar 18 01:15:27 1999
@@ -379,7 +379,7 @@
     debug(32, 1) ("aioSync: flushing pending I/O operations\n");
     do {
 	aioCheckCallbacks();
-    } while (aio_operations_pending());
+    } while (aio_sync());
     debug(32, 1) ("aioSync: done\n");
 }
 
Index: squid/src/protos.h
diff -u squid/src/protos.h:1.1.1.37.2.1 squid/src/protos.h:1.1.1.37.2.2
--- squid/src/protos.h:1.1.1.37.2.1	Sat Mar  6 22:40:28 1999
+++ squid/src/protos.h	Thu Mar 18 01:15:27 1999
@@ -77,6 +77,8 @@
 extern int aio_opendir(const char *, aio_result_t *);
 extern aio_result_t *aio_poll_done(void);
 extern int aio_operations_pending(void);
+extern int aio_overloaded(void);
+extern int aio_sync(void);
 
 extern void aioCancel(int, void *);
 extern void aioOpen(const char *, int, mode_t, AIOCB *, void *, void *);
Index: squid/src/store.c
diff -u squid/src/store.c:1.1.1.36 squid/src/store.c:1.1.1.36.2.1
--- squid/src/store.c:1.1.1.36	Sun Feb 14 23:30:08 1999
+++ squid/src/store.c	Thu Mar 18 01:15:27 1999
@@ -518,6 +518,10 @@
 	 * out the object yet.
 	 */
 	return 1;
+#if USE_ASYNC_IO
+    } else if (aio_overloaded()) {
+	debug(20, 2) ("storeCheckCachable: NO: Async-IO overloaded\n");
+#endif
     } else if (storeTooManyDiskFilesOpen()) {
 	debug(20, 2) ("storeCheckCachable: NO: too many disk files open\n");
 	store_check_cachable_hist.no.too_many_open_files++;