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 #include "cpulimit.h"
  27 #include "util.h"
  28 #include "log.h"
  29
  30 #ifdef HAVE_SIGXCPU
  31
  32 #include <errno.h>
  33 #include <stdio.h>
  34 #include <string.h>
  35 #include <assert.h>
  36 #include <sys/time.h>
  37 #include <unistd.h>
  38 #include <signal.h>
  39
  40 #ifdef HAVE_SYS_RESOURCE_H
  41 #include <sys/resource.h>
  42 #endif
  43
  44 /* This module implements a watchdog that makes sure that the current
  45  * process doesn't consume more than 70% CPU time for 10 seconds. This
  46  * is very useful when using SCHED_FIFO scheduling which effectively
  47  * disables multitasking. */
  48
  49 /* Method of operation: Using SIGXCPU a signal handler is called every
  50  * 10s process CPU time. That function checks if less than 14s system
  51  * time have passed. In that case, it tries to contact the main event
  52  * loop through a pipe. After two additional seconds it is checked
  53  * whether the main event loop contact was successful. If not, the
  54  * program is terminated forcibly. */
  55
  56 /* Utilize this much CPU time at maximum */
  57 #define CPUTIME_PERCENT 70
  58
  59 /* Check every 10s */
  60 #define CPUTIME_INTERVAL_SOFT (10)
  61
  62 /* Recheck after 2s */
  63 #define CPUTIME_INTERVAL_HARD (2)
  64
  65 /* Time of the last CPU load check */
  66 static time_t last_time = 0;
  67
  68 /* Pipe for communicating with the main loop */
  69 static int the_pipe[2] = {-1, -1};
  70
  71 /* Main event loop and IO event for the FIFO */
  72 static pa_mainloop_api *api = NULL;
  73 static pa_io_event *io_event = NULL;
  74
  75 /* Saved sigaction struct for SIGXCPU */
  76 static struct sigaction sigaction_prev;
  77
  78 /* Nonzero after pa_cpu_limit_init() */
  79 static int installed = 0;
  80
  81 /* The current state of operation */
  82 static enum  {
  83     PHASE_IDLE,   /* Normal state */
  84     PHASE_SOFT    /* After CPU overload has been detected */
  85 } phase = PHASE_IDLE;
  86
  87 /* Reset the SIGXCPU timer to the next t seconds */
  88 static void reset_cpu_time(int t) {
  89     int r;
  90     long n;
  91     struct rlimit rl;
  92     struct rusage ru;
  93
  94     /* Get the current CPU time of the current process */
  95     r = getrusage(RUSAGE_SELF, &ru);
  96     assert(r >= 0);
  97
  98     n = ru.ru_utime.tv_sec + ru.ru_stime.tv_sec + t;
  99
 100     r = getrlimit(RLIMIT_CPU, &rl);
 101     assert(r >= 0);
 102
 103     rl.rlim_cur = n;
 104     r = setrlimit(RLIMIT_CPU, &rl);
 105     assert(r >= 0);
 106 }
 107
 108 /* A simple, thread-safe puts() work-alike */
 109 static void write_err(const char *p) {
 110     pa_loop_write(2, p, strlen(p));
 111 }
 112
 113 /* The signal handler, called on every SIGXCPU */
 114 static void signal_handler(int sig) {
 115     assert(sig == SIGXCPU);
 116
 117     if (phase == PHASE_IDLE) {
 118         time_t now;
 119
 120 #ifdef PRINT_CPU_LOAD
 121         char t[256];
 122 #endif
 123
 124         time(&now);
 125
 126 #ifdef PRINT_CPU_LOAD
 127         snprintf(t, sizeof(t), "Using %0.1f%% CPU\n", (double)CPUTIME_INTERVAL_SOFT/(now-last_time)*100);
 128         write_err(t);
 129 #endif
 130
 131         if (CPUTIME_INTERVAL_SOFT >= ((now-last_time)*(double)CPUTIME_PERCENT/100)) {
 132             static const char c = 'X';
 133
 134             write_err("Soft CPU time limit exhausted, terminating.\n");
 135
 136             /* Try a soft cleanup */
 137             write(the_pipe[1], &c, sizeof(c));
 138             phase = PHASE_SOFT;
 139             reset_cpu_time(CPUTIME_INTERVAL_HARD);
 140
 141         } else {
 142
 143             /* Everything's fine */
 144             reset_cpu_time(CPUTIME_INTERVAL_SOFT);
 145             last_time = now;
 146         }
 147
 148     } else if (phase == PHASE_SOFT) {
 149         write_err("Hard CPU time limit exhausted, terminating forcibly.\n");
 150         _exit(1); /* Forced exit */
 151     }
 152 }
 153
 154 /* Callback for IO events on the FIFO */
 155 static void callback(pa_mainloop_api*m, pa_io_event*e, int fd, pa_io_event_flags f, void *userdata) {
 156     char c;
 157     assert(m && e && f == PA_IO_EVENT_INPUT && e == io_event && fd == the_pipe[0]);
 158     read(the_pipe[0], &c, sizeof(c));
 159     m->quit(m, 1); /* Quit the main loop */
 160 }
 161
 162 /* Initializes CPU load limiter */
 163 int pa_cpu_limit_init(pa_mainloop_api *m) {
 164     struct sigaction sa;
 165     assert(m && !api && !io_event && the_pipe[0] == -1 && the_pipe[1] == -1 && !installed);
 166
 167     time(&last_time);
 168
 169     /* Prepare the main loop pipe */
 170     if (pipe(the_pipe) < 0) {
 171         pa_log(__FILE__": pipe() failed: %s\n", strerror(errno));
 172         return -1;
 173     }
 174
 175     pa_make_nonblock_fd(the_pipe[0]);
 176     pa_make_nonblock_fd(the_pipe[1]);
 177     pa_fd_set_cloexec(the_pipe[0], 1);
 178     pa_fd_set_cloexec(the_pipe[1], 1);
 179
 180     api = m;
 181     io_event = api->io_new(m, the_pipe[0], PA_IO_EVENT_INPUT, callback, NULL);
 182
 183     phase = PHASE_IDLE;
 184
 185     /* Install signal handler for SIGXCPU */
 186     memset(&sa, 0, sizeof(sa));
 187     sa.sa_handler = signal_handler;
 188     sigemptyset(&sa.sa_mask);
 189     sa.sa_flags = SA_RESTART;
 190
 191     if (sigaction(SIGXCPU, &sa, &sigaction_prev) < 0) {
 192         pa_cpu_limit_done();
 193         return -1;
 194     }
 195
 196     installed = 1;
 197
 198     reset_cpu_time(CPUTIME_INTERVAL_SOFT);
 199
 200     return 0;
 201 }
 202
 203 /* Shutdown CPU load limiter */
 204 void pa_cpu_limit_done(void) {
 205     int r;
 206
 207     if (io_event) {
 208         assert(api);
 209         api->io_free(io_event);
 210         io_event = NULL;
 211         api = NULL;
 212     }
 213
 214     if (the_pipe[0] >= 0)
 215         close(the_pipe[0]);
 216     if (the_pipe[1] >= 0)
 217         close(the_pipe[1]);
 218     the_pipe[0] = the_pipe[1] = -1;
 219
 220     if (installed) {
 221         r = sigaction(SIGXCPU, &sigaction_prev, NULL);
 222         assert(r >= 0);
 223         installed = 0;
 224     }
 225 }
 226
 227 #else /* HAVE_SIGXCPU */
 228
 229 int pa_cpu_limit_init(PA_GCC_UNUSED pa_mainloop_api *m) {
 230     return 0;
 231 }
 232
 233 void pa_cpu_limit_done(void) {
 234 }
 235
 236 #endif