From 0a2bbc528b7865b08139155e0316738a717c4e42 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Wed, 17 Nov 2004 00:05:25 +0000
Subject: * some commenting work * add new field "read_only" to memory blocks *
 add new API function pa_context_get_server() * filter capture data through
 mcalign on client * make module-tunnel use pa_socket_client_new_string()
 instead of using pa_resolve_server() directly. * remove pa_resolve_server() *
 remove debug.h and replace it by a macro definition on the gcc command line *
 some strbuf cleanups * small fixes in pa_stream for cleanup when server dies
 * new CLI command "load-sample-dir-lazy" * send FQDN as part of server info *
 rework mcalign, this time with memory block merging * fix iochannel cleanup
 when connection dies * check getaddrinfo() results

git-svn-id: file:///home/lennart/svn/public/pulseaudio/trunk@286 fefdeb5f-60dc-0310-8127-8f9354f1896f
---
 polyp/cpulimit.c | 47 +++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 41 insertions(+), 6 deletions(-)

(limited to 'polyp/cpulimit.c')

diff --git a/polyp/cpulimit.c b/polyp/cpulimit.c
index fcbbaf3d..78dc5e1f 100644
--- a/polyp/cpulimit.c
+++ b/polyp/cpulimit.c
@@ -32,30 +32,58 @@
 #include "util.h"
 #include "log.h"
 
+
+/* This module implements a watchdog that makes sure that the current
+ * process doesn't consume more than 70% CPU time for 10 seconds. This
+ * is very useful when using SCHED_FIFO scheduling which effectively
+ * disables multitasking. */
+
+/* Method of operation: Using SIGXCPU a signal handler is called every
+ * 10s process CPU time. That function checks if less than 14s system
+ * time have passed. In that case, it tries to contact the main event
+ * loop through a pipe. After two additional seconds it is checked
+ * whether the main event loop contact was successful. If not, the
+ * program is terminated forcibly. */
+
 /* Utilize this much CPU time at maximum */
 #define CPUTIME_PERCENT 70
 
+/* Check every 10s */
 #define CPUTIME_INTERVAL_SOFT (10)
+
+/* Recheck after 2s */
 #define CPUTIME_INTERVAL_HARD (2)
 
+/* Time of the last CPU load check */
 static time_t last_time = 0;
+
+/* Pipe for communicating with the main loop */
 static int the_pipe[2] = {-1, -1};
+
+/* Main event loop and IO event for the FIFO */
 static struct pa_mainloop_api *api = NULL;
 static struct pa_io_event *io_event = NULL;
+
+/* Saved sigaction struct for SIGXCPU */
 static struct sigaction sigaction_prev;
-static int installed = 0;
 
+/* Nonzero after pa_cpu_limit_init() */
+static int installed = 0; 
+
+/* The current state of operation */
 static enum  {
-    PHASE_IDLE,
-    PHASE_SOFT
+    PHASE_IDLE,   /* Normal state */
+    PHASE_SOFT    /* After CPU overload has been detected */
 } phase = PHASE_IDLE;
 
+/* Reset the SIGXCPU timer to the next t seconds */
 static void reset_cpu_time(int t) {
     int r;
     long n;
     struct rlimit rl;
     struct rusage ru;
 
+    /* Get the current CPU time of the current process */
     r = getrusage(RUSAGE_SELF, &ru);
     assert(r >= 0);
 
@@ -69,10 +97,12 @@ static void reset_cpu_time(int t) {
     assert(r >= 0);
 }
 
+/* A simple, thread-safe puts() work-alike */
 static void write_err(const char *p) {
     pa_loop_write(2, p, strlen(p));
 }
 
+/* The signal handler, called on every SIGXCPU */
 static void signal_handler(int sig) {
     assert(sig == SIGXCPU);
 
@@ -109,23 +139,26 @@ static void signal_handler(int sig) {
         
     } else if (phase == PHASE_SOFT) {
         write_err("Hard CPU time limit exhausted, terminating forcibly.\n");
-        _exit(1);
+        _exit(1); /* Forced exit */
     }
 }
 
+/* Callback for IO events on the FIFO */
 static void callback(struct pa_mainloop_api*m, struct pa_io_event*e, int fd, enum pa_io_event_flags f, void *userdata) {
     char c;
     assert(m && e && f == PA_IO_EVENT_INPUT && e == io_event && fd == the_pipe[0]);
     read(the_pipe[0], &c, sizeof(c));
-    m->quit(m, 1);
+    m->quit(m, 1); /* Quit the main loop */
 }
 
+/* Initializes CPU load limiter */
 int pa_cpu_limit_init(struct pa_mainloop_api *m) {
     struct sigaction sa;
-    assert(m && !api && !io_event && the_pipe[0] == -1 && the_pipe[1] == -1);
+    assert(m && !api && !io_event && the_pipe[0] == -1 && the_pipe[1] == -1 && !installed);
     
     time(&last_time);
 
+    /* Prepare the main loop pipe */
     if (pipe(the_pipe) < 0) {
         pa_log(__FILE__": pipe() failed: %s\n", strerror(errno));
         return -1;
@@ -141,6 +174,7 @@ int pa_cpu_limit_init(struct pa_mainloop_api *m) {
 
     phase = PHASE_IDLE;
 
+    /* Install signal handler for SIGXCPU */
     memset(&sa, 0, sizeof(sa));
     sa.sa_handler = signal_handler;
     sigemptyset(&sa.sa_mask);
@@ -158,6 +192,7 @@ int pa_cpu_limit_init(struct pa_mainloop_api *m) {
     return 0;
 }
 
+/* Shutdown CPU load limiter */
 void pa_cpu_limit_done(void) {
     int r;
 
-- 
cgit