code.delx.au - pulseaudio/blob - polyp/cpulimit.c

   1 /* $Id$ */
   2
   3 /***
   4   This file is part of polypaudio.
   5
   6   polypaudio is free software; you can redistribute it and/or modify
   7   it under the terms of the GNU Lesser General Public License as
   8   published by the Free Software Foundation; either version 2 of the
   9   License, or (at your option) any later version.
  10
  11   polypaudio is distributed in the hope that it will be useful, but
  12   WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14   General Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public
  17   License along with polypaudio; if not, write to the Free Software
  18   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
  19   USA.
  20 ***/
  21
  22 #ifdef HAVE_CONFIG_H
  23 #include <config.h>
  24 #endif
  25
  26 #ifdef HAVE_SIGXCPU
  27
  28 #include <errno.h>
  29 #include <stdio.h>
  30 #include <string.h>
  31 #include <assert.h>
  32 #include <sys/time.h>
  33 #include <unistd.h>
  34 #include <signal.h>
  35
  36 #ifdef HAVE_SYS_RESOURCE_H
  37 #include <sys/resource.h>
  38 #endif
  39
  40 #include "cpulimit.h"
  41 #include "util.h"
  42 #include "log.h"
  43
  44
  45 /* This module implements a watchdog that makes sure that the current
  46  * process doesn't consume more than 70% CPU time for 10 seconds. This
  47  * is very useful when using SCHED_FIFO scheduling which effectively
  48  * disables multitasking. */
  49
  50 /* Method of operation: Using SIGXCPU a signal handler is called every
  51  * 10s process CPU time. That function checks if less than 14s system
  52  * time have passed. In that case, it tries to contact the main event
  53  * loop through a pipe. After two additional seconds it is checked
  54  * whether the main event loop contact was successful. If not, the
  55  * program is terminated forcibly. */
  56
  57 /* Utilize this much CPU time at maximum */
  58 #define CPUTIME_PERCENT 70
  59
  60 /* Check every 10s */
  61 #define CPUTIME_INTERVAL_SOFT (10)
  62
  63 /* Recheck after 2s */
  64 #define CPUTIME_INTERVAL_HARD (2)
  65
  66 /* Time of the last CPU load check */
  67 static time_t last_time = 0;
  68
  69 /* Pipe for communicating with the main loop */
  70 static int the_pipe[2] = {-1, -1};
  71
  72 /* Main event loop and IO event for the FIFO */
  73 static struct pa_mainloop_api *api = NULL;
  74 static struct pa_io_event *io_event = NULL;
  75
  76 /* Saved sigaction struct for SIGXCPU */
  77 static struct sigaction sigaction_prev;
  78
  79 /* Nonzero after pa_cpu_limit_init() */
  80 static int installed = 0;
  81
  82 /* The current state of operation */
  83 static enum  {
  84     PHASE_IDLE,   /* Normal state */
  85     PHASE_SOFT    /* After CPU overload has been detected */
  86 } phase = PHASE_IDLE;
  87
  88 /* Reset the SIGXCPU timer to the next t seconds */
  89 static void reset_cpu_time(int t) {
  90     int r;
  91     long n;
  92     struct rlimit rl;
  93     struct rusage ru;
  94
  95     /* Get the current CPU time of the current process */
  96     r = getrusage(RUSAGE_SELF, &ru);
  97     assert(r >= 0);
  98
  99     n = ru.ru_utime.tv_sec + ru.ru_stime.tv_sec + t;
 100
 101     r = getrlimit(RLIMIT_CPU, &rl);
 102     assert(r >= 0);
 103
 104     rl.rlim_cur = n;
 105     r = setrlimit(RLIMIT_CPU, &rl);
 106     assert(r >= 0);
 107 }
 108
 109 /* A simple, thread-safe puts() work-alike */
 110 static void write_err(const char *p) {
 111     pa_loop_write(2, p, strlen(p));
 112 }
 113
 114 /* The signal handler, called on every SIGXCPU */
 115 static void signal_handler(int sig) {
 116     assert(sig == SIGXCPU);
 117
 118     if (phase == PHASE_IDLE) {
 119         time_t now;
 120
 121 #ifdef PRINT_CPU_LOAD
 122         char t[256];
 123 #endif
 124
 125         time(&now);
 126
 127 #ifdef PRINT_CPU_LOAD
 128         snprintf(t, sizeof(t), "Using %0.1f%% CPU\n", (double)CPUTIME_INTERVAL_SOFT/(now-last_time)*100);
 129         write_err(t);
 130 #endif
 131
 132         if (CPUTIME_INTERVAL_SOFT >= ((now-last_time)*(double)CPUTIME_PERCENT/100)) {
 133             static const char c = 'X';
 134
 135             write_err("Soft CPU time limit exhausted, terminating.\n");
 136
 137             /* Try a soft cleanup */
 138             write(the_pipe[1], &c, sizeof(c));
 139             phase = PHASE_SOFT;
 140             reset_cpu_time(CPUTIME_INTERVAL_HARD);
 141
 142         } else {
 143
 144             /* Everything's fine */
 145             reset_cpu_time(CPUTIME_INTERVAL_SOFT);
 146             last_time = now;
 147         }
 148
 149     } else if (phase == PHASE_SOFT) {
 150         write_err("Hard CPU time limit exhausted, terminating forcibly.\n");
 151         _exit(1); /* Forced exit */
 152     }
 153 }
 154
 155 /* Callback for IO events on the FIFO */
 156 static void callback(struct pa_mainloop_api*m, struct pa_io_event*e, int fd, enum pa_io_event_flags f, void *userdata) {
 157     char c;
 158     assert(m && e && f == PA_IO_EVENT_INPUT && e == io_event && fd == the_pipe[0]);
 159     read(the_pipe[0], &c, sizeof(c));
 160     m->quit(m, 1); /* Quit the main loop */
 161 }
 162
 163 /* Initializes CPU load limiter */
 164 int pa_cpu_limit_init(struct pa_mainloop_api *m) {
 165     struct sigaction sa;
 166     assert(m && !api && !io_event && the_pipe[0] == -1 && the_pipe[1] == -1 && !installed);
 167
 168     time(&last_time);
 169
 170     /* Prepare the main loop pipe */
 171     if (pipe(the_pipe) < 0) {
 172         pa_log(__FILE__": pipe() failed: %s\n", strerror(errno));
 173         return -1;
 174     }
 175
 176     pa_make_nonblock_fd(the_pipe[0]);
 177     pa_make_nonblock_fd(the_pipe[1]);
 178     pa_fd_set_cloexec(the_pipe[0], 1);
 179     pa_fd_set_cloexec(the_pipe[1], 1);
 180
 181     api = m;
 182     io_event = api->io_new(m, the_pipe[0], PA_IO_EVENT_INPUT, callback, NULL);
 183
 184     phase = PHASE_IDLE;
 185
 186     /* Install signal handler for SIGXCPU */
 187     memset(&sa, 0, sizeof(sa));
 188     sa.sa_handler = signal_handler;
 189     sigemptyset(&sa.sa_mask);
 190     sa.sa_flags = SA_RESTART;
 191
 192     if (sigaction(SIGXCPU, &sa, &sigaction_prev) < 0) {
 193         pa_cpu_limit_done();
 194         return -1;
 195     }
 196
 197     installed = 1;
 198
 199     reset_cpu_time(CPUTIME_INTERVAL_SOFT);
 200
 201     return 0;
 202 }
 203
 204 /* Shutdown CPU load limiter */
 205 void pa_cpu_limit_done(void) {
 206     int r;
 207
 208     if (io_event) {
 209         assert(api);
 210         api->io_free(io_event);
 211         io_event = NULL;
 212         api = NULL;
 213     }
 214
 215     if (the_pipe[0] >= 0)
 216         close(the_pipe[0]);
 217     if (the_pipe[1] >= 0)
 218         close(the_pipe[1]);
 219     the_pipe[0] = the_pipe[1] = -1;
 220
 221     if (installed) {
 222         r = sigaction(SIGXCPU, &sigaction_prev, NULL);
 223         assert(r >= 0);
 224         installed = 0;
 225     }
 226 }
 227
 228 #else /* HAVE_SIGXCPU */
 229
 230 struct pa_mainloop_api;
 231
 232 int pa_cpu_limit_init(struct pa_mainloop_api *m) {
 233     return 0;
 234 }
 235
 236 void pa_cpu_limit_done(void) {
 237 }
 238
 239 #endif