Commit 3b84b357 authored by Evgeny Kotkov's avatar Evgeny Kotkov
Browse files

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.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1801636 13f79535-47bb-0310-9956-ffa450edef68
parent 1c96d681

server/mpm/winnt/child.c

+20 −11
Original line number Diff line number Diff line
@@ -1260,22 +1260,31 @@ void child_main(apr_pool_t *pconf, DWORD parent_pid) 
        }

    }



    /* 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));

            /* 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.");