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53436f42f4
Asterisk goes into a busy loop, the machine will be recoverable. We'd still need to do a restart to put Asterisk back into high priority mode, but at least a reboot won't be required. (Closes issue #11559) git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@93804 65c4cc65-6c06-0410-ace0-fbb531ad65f3
85 lines
2.8 KiB
C
85 lines
2.8 KiB
C
/*
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* Asterisk -- An open source telephony toolkit.
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*
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* Copyright (C) 2007, Digium, Inc.
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*
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* Tilghman Lesher <tlesher AT digium DOT com>
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*
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* See http://www.asterisk.org for more information about
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* the Asterisk project. Please do not directly contact
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* any of the maintainers of this project for assistance;
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* the project provides a web site, mailing lists and IRC
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* channels for your use.
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*
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* This program is free software, distributed under the terms of
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* the GNU General Public License Version 2. See the LICENSE file
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* at the top of the source tree.
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*/
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <sys/time.h>
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#include <sys/resource.h>
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#include <utime.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <stdlib.h>
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/*!\brief
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* At one time, canaries were carried along with coal miners down
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* into a mine. Their purpose was to alert the miners when they
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* had drilled into a pocket of methane gas or another noxious
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* substance. The canary, being the most sensitive animal would
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* immediately fall over. Seeing this, the miners could take
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* action to escape the mine, seeing an imminent danger.
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*
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* This process serves a similar purpose, though with the realtime
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* priority being the reason. When a thread starts running away
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* with the processor, it is typically difficult to tell what
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* thread caused the problem, as the machine acts as if it is
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* locked up (in fact, what has happened is that Asterisk runs at
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* a higher priority than even the login shell, so the runaway
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* thread hogs all available CPU time.
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*
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* If that happens, this canary process will cease to get any
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* process time, which we can monitor with a realtime thread in
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* Asterisk. Should that happen, that monitoring thread may take
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* immediate action to slow down Asterisk to regular priority,
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* thus allowing an administrator to login to the system and
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* restart Asterisk or perhaps take another course of action
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* (such as retrieving a backtrace to let the developers know
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* what precisely went wrong).
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*
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* Note that according to POSIX.1, all threads inside a single
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* process must share the same priority, so when the monitoring
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* thread deprioritizes itself, it deprioritizes all threads at
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* the same time. This is also why this canary must exist as a
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* completely separate process and not simply as a thread within
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* Asterisk itself.
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*/
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int main(int argc, char *argv[])
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{
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int fd;
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/* Run at normal priority */
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setpriority(PRIO_PROCESS, 0, 0);
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for (;;) {
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/* Update the modification times (checked from Asterisk) */
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if (utime(argv[1], NULL)) {
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/* Recreate the file if it doesn't exist */
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if ((fd = open(argv[1], O_RDWR | O_TRUNC | O_CREAT)) > -1)
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close(fd);
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else
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exit(1);
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continue;
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}
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/* Run occasionally */
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sleep(5);
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}
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/* Never reached */
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return 0;
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}
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