this sounds awfully familiar...
while I'm still working on getting a win32 build up and running, can
somebody try the hook order thing with this patch?
thanks.
--Geoff
-------- Original Message --------
Subject: [PATCH] apr_thread_cond_wait bug/problem on WIN32
Date: Fri, 05 Mar 2004 15:46:36 +0100
From: Klaus Keppler <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
[RESENT because I got no response for about two weeks...]
Hello,
having spent several hours on one problem only occuring on WIN32
platform I found following bug(?) with locks/win32/thread_cond.c.
In my application I use the function apr_thread_cond_wait in a
very similar context like httpd2's worker-mpm (fdqueue.c ->
ap_queue_pop).
Heavy load tests (using apache's ab) worked well under linux,
but on win32 I experienced deadlocks after some seconds.
Debugging brought me to the source of apr_thread_cond_wait();
as you can see the function "apr_thread_mutex_unlock(mutex)"
is called every time the while(1)-loop is run.
I think this shouldn't be a problem in general (since an unlocked
mutex can't be unlocked once more), but at least for *me* it *did*
cause trouble. And I am no windows guru so I don't know
if/how windows bothers about multiple unlocking.
After changing the code to unlock the mutex only once
everything worked very fine. :-)
I tested the patch with Win2K.
Without patch, my application ran (with 2 worker threads) only up to 20
loops before ending in an deadlock; now I tested 200.000 loops without
problems.
Btw: another approach would be to add a counter to every mutex and
ignore unlock calls when counter==0. Would this make sense?
Klaus
--- locks/win32/thread_cond-old.c Mon Feb 23 11:56:45 2004
+++ locks/win32/thread_cond.c Mon Feb 23 12:01:46 2004
@@ -85,6 +85,8 @@
{
DWORD res;
+ int unlock_once = 1;
+
while (1) {
res = WaitForSingleObject(cond->mutex, INFINITE);
if (res != WAIT_OBJECT_0) {
@@ -93,7 +95,10 @@
cond->num_waiting++;
ReleaseMutex(cond->mutex);
- apr_thread_mutex_unlock(mutex);
+ if (unlock_once) {
+ unlock_once = 0;
+ apr_thread_mutex_unlock(mutex);
+ }
res = WaitForSingleObject(cond->event, INFINITE);
cond->num_waiting--;
if (res != WAIT_OBJECT_0) {
@@ -125,6 +130,8 @@
DWORD res;
DWORD timeout_ms = (DWORD) apr_time_as_msec(timeout);
+ int unlock_once = 1;
+
while (1) {
res = WaitForSingleObject(cond->mutex, timeout_ms);
if (res != WAIT_OBJECT_0) {
@@ -136,7 +143,10 @@
cond->num_waiting++;
ReleaseMutex(cond->mutex);
- apr_thread_mutex_unlock(mutex);
+ if (unlock_once) {
+ unlock_once = 0;
+ apr_thread_mutex_unlock(mutex);
+ }
res = WaitForSingleObject(cond->event, timeout_ms);
cond->num_waiting--;
if (res != WAIT_OBJECT_0) {
--
Klaus Keppler <[EMAIL PROTECTED]>
Student of Computer Science at University Erlangen-Nurember, Germany
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