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Date: Thu, 26 Sep 2002 02:11:59 +0200 (CEST)
From: Dirk-Willem van Gulik <dirkx@webweaving.org>
To: dev@httpd.apache.org
Subject: [PATCH] Alerting when fnctl is going bad 
Message-ID: <20020926021132.U80210-100000@foem.leiden.webweaving.org>
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Now this may be a bit linux specific - but I'd like to get something like
this in; if needed with a #ifdef DIAG or on a per platform basis.

It is just something I've found to come in handy at various times - in
particular on Linux and with lots of heavy PHP or mod_perl.

This patch does two things

->	Collapes the near identical mutex_fcnt on/off functions
	into one.

->	Makes the wait loop no longer endless - but causes it
	to bail out (and emit some warnings ahead of time) after
	a couple of thousand consequituve EINTRs.

Does this make sense ? Objections ?

Dw

Index: http_main.c
===================================================================
RCS file: /home/cvs/apache-1.3/src/main/http_main.c,v
retrieving revision 1.592
diff -u -r1.592 http_main.c
--- http_main.c	21 Sep 2002 17:18:34 -0000	1.592
+++ http_main.c	26 Sep 2002 00:07:20 -0000
@@ -885,37 +885,51 @@
     unlink(ap_lock_fname);
 }

-static void accept_mutex_on_fcntl(void)
+static void accept_mutex(struct flock * flag)
 {
-    int ret;
-
-    while ((ret = fcntl(lock_fd, F_SETLKW, &lock_it)) < 0 && errno == EINTR) {
-	/* nop */
+    int ret,count = 0;
+    while ((ret = fcntl(lock_fd, F_SETLKW, flag)) < 0 && errno == EINTR) {
+	count++;
+	if (count & 0x20) {
+		ap_log_error(APLOG_MARK,
+			APLOG_INFO|APLOG_NOERRNO,server_conf,
+				"fcntl_mutex(%slock): many EINTR's, keep trying",
+				flag->l_type == F_UNLCK ? "un" : "");
+		if (count > 5000) {
+			ap_log_error(APLOG_MARK,APLOG_EMERG,server_conf,
+				"fcntl_mutex(%slock): %d EINTR's in"
+				" a row, child exiting...",
+				flag->l_type == F_UNLCK ? "un" : "",count);
+			clean_child_exit(APEXIT_CHILDFATAL);
+    		}
+	}
     }

     if (ret < 0) {
 	ap_log_error(APLOG_MARK, APLOG_EMERG, server_conf,
-		    "fcntl: F_SETLKW: Error getting accept lock, exiting!  "
-		    "Perhaps you need to use the LockFile directive to place "
-		    "your lock file on a local disk!");
+		"fcntl: F_SETLKW: Error %slocking accept lock, exiting!  "
+		"Perhaps you need to use the LockFile directive to place "
+		"your lock file on a local disk!",
+		flag->l_type == F_UNLCK ? "un" : "");
 	clean_child_exit(APEXIT_CHILDFATAL);
     }
+
+    if (count > 50) {
+	ap_log_error(APLOG_MARK,APLOG_WARNING|APLOG_NOERRNO,server_conf,
+		"fcntl_mutex(%slock): got EINTR %d consequitive times, "
+		"and finally succeeded",
+		flag->l_type == F_UNLCK ? "un" : "",count);
+   }
 }

-static void accept_mutex_off_fcntl(void)
+static void accept_mutex_on_fcntl(void)
 {
-    int ret;
+    return accept_mutex(&lock_it);
+}

-    while ((ret = fcntl(lock_fd, F_SETLKW, &unlock_it)) < 0 && errno == EINTR) {
-	/* nop */
-    }
-    if (ret < 0) {
-	ap_log_error(APLOG_MARK, APLOG_EMERG, server_conf,
-		    "fcntl: F_SETLKW: Error freeing accept lock, exiting!  "
-		    "Perhaps you need to use the LockFile directive to place "
-		    "your lock file on a local disk!");
-	clean_child_exit(APEXIT_CHILDFATAL);
-    }
+static void accept_mutex_off_fcntl(void)
+{
+    return accept_mutex(&unlock_it);
 }

 accept_mutex_methods_s accept_mutex_fcntl_s = {