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Posted to cvs@httpd.apache.org by ko...@apache.org on 2017/07/11 16:46:47 UTC
svn commit: r1801636 - /httpd/httpd/trunk/server/mpm/winnt/child.c
Author: kotkov
Date: Tue Jul 11 16:46:47 2017
New Revision: 1801636
URL: http://svn.apache.org/viewvc?rev=1801636&view=rev
Log:
mpm_winnt: Avoid using TerminateThread() in case the shutdown routine
hits a timeout while waiting for the worker threads to exit.
Using TerminateThread() can have dangerous consequences such as deadlocks —
say, if the the thread is terminated while holding a lock or a heap lock
in the middle of HeapAlloc(), as these locks would not be released.
Or it can corrupt the application state and cause a crash.
(See https://msdn.microsoft.com/en-us/library/windows/desktop/ms686717)
Rework the code to call TerminateProcess() in the described circumstances
and leave the cleanup to the operating system.
Modified:
httpd/httpd/trunk/server/mpm/winnt/child.c
Modified: httpd/httpd/trunk/server/mpm/winnt/child.c
URL: http://svn.apache.org/viewvc/httpd/httpd/trunk/server/mpm/winnt/child.c?rev=1801636&r1=1801635&r2=1801636&view=diff
==============================================================================
--- httpd/httpd/trunk/server/mpm/winnt/child.c (original)
+++ httpd/httpd/trunk/server/mpm/winnt/child.c Tue Jul 11 16:46:47 2017
@@ -1260,21 +1260,30 @@ void child_main(apr_pool_t *pconf, DWORD
}
}
- /* Kill remaining threads off the hard way */
if (threads_created) {
ap_log_error(APLOG_MARK, APLOG_NOTICE, APR_SUCCESS, ap_server_conf, APLOGNO(00363)
- "Child: Terminating %d threads that failed to exit.",
+ "Child: Waiting for %d threads timed out, terminating process.",
threads_created);
- }
- for (i = 0; i < threads_created; i++) {
- int *idx;
- TerminateThread(child_handles[i], 1);
- CloseHandle(child_handles[i]);
- /* Reset the scoreboard entry for the thread we just whacked */
- idx = apr_hash_get(ht, &child_handles[i], sizeof(HANDLE));
- if (idx) {
- ap_update_child_status_from_indexes(0, *idx, SERVER_DEAD, NULL);
+ for (i = 0; i < threads_created; i++) {
+ /* Reset the scoreboard entries for the threads. */
+ int *idx = apr_hash_get(ht, &child_handles[i], sizeof(HANDLE));
+ if (idx) {
+ ap_update_child_status_from_indexes(0, *idx, SERVER_DEAD, NULL);
+ }
}
+ /* We can't wait for any longer, but still have some threads remaining.
+ *
+ * The only thing we can do is terminate the process and let the OS
+ * perform the required cleanup. Terminate with exit code 0, as we do
+ * not want the parent process to restart the child. Note that we use
+ * TerminateProcess() instead of ExitProcess(), as the latter function
+ * causes all DLLs to be unloaded, and it can potentially deadlock if
+ * a DLL unload handler tries to acquire the same lock that is being
+ * held by one of the remaining worker threads.
+ *
+ * See https://msdn.microsoft.com/en-us/library/windows/desktop/ms682658
+ */
+ TerminateProcess(GetCurrentProcess(), 0);
}
ap_log_error(APLOG_MARK, APLOG_NOTICE, APR_SUCCESS, ap_server_conf, APLOGNO(00364)
"Child: All worker threads have exited.");