code.delx.au - pulseaudio/blob - src/daemon/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 <polyp/error.h>
  27
  28 #include <polypcore/core-util.h>
  29 #include <polypcore/log.h>
  30
  31 #include "cpulimit.h"
  32
  33 #ifdef HAVE_SIGXCPU
  34
  35 #include <errno.h>
  36 #include <stdio.h>
  37 #include <string.h>
  38 #include <assert.h>
  39 #include <sys/time.h>
  40 #include <unistd.h>
  41 #include <signal.h>
  42
  43 #ifdef HAVE_SYS_RESOURCE_H
  44 #include <sys/resource.h>
  45 #endif
  46
  47 /* This module implements a watchdog that makes sure that the current
  48  * process doesn't consume more than 70% CPU time for 10 seconds. This
  49  * is very useful when using SCHED_FIFO scheduling which effectively
  50  * disables multitasking. */
  51
  52 /* Method of operation: Using SIGXCPU a signal handler is called every
  53  * 10s process CPU time. That function checks if less than 14s system
  54  * time have passed. In that case, it tries to contact the main event
  55  * loop through a pipe. After two additional seconds it is checked
  56  * whether the main event loop contact was successful. If not, the
  57  * program is terminated forcibly. */
  58
  59 /* Utilize this much CPU time at maximum */
  60 #define CPUTIME_PERCENT 70
  61
  62 /* Check every 10s */
  63 #define CPUTIME_INTERVAL_SOFT (10)
  64
  65 /* Recheck after 2s */
  66 #define CPUTIME_INTERVAL_HARD (2)
  67
  68 /* Time of the last CPU load check */
  69 static time_t last_time = 0;
  70
  71 /* Pipe for communicating with the main loop */
  72 static int the_pipe[2] = {-1, -1};
  73
  74 /* Main event loop and IO event for the FIFO */
  75 static pa_mainloop_api *api = NULL;
  76 static pa_io_event *io_event = NULL;
  77
  78 /* Saved sigaction struct for SIGXCPU */
  79 static struct sigaction sigaction_prev;
  80
  81 /* Nonzero after pa_cpu_limit_init() */
  82 static int installed = 0;
  83
  84 /* The current state of operation */
  85 static enum  {
  86     PHASE_IDLE,   /* Normal state */
  87     PHASE_SOFT    /* After CPU overload has been detected */
  88 } phase = PHASE_IDLE;
  89
  90 /* Reset the SIGXCPU timer to the next t seconds */
  91 static void reset_cpu_time(int t) {
  92     int r;
  93     long n;
  94     struct rlimit rl;
  95     struct rusage ru;
  96
  97     /* Get the current CPU time of the current process */
  98     r = getrusage(RUSAGE_SELF, &ru);
  99     assert(r >= 0);
 100
 101     n = ru.ru_utime.tv_sec + ru.ru_stime.tv_sec + t;
 102
 103     r = getrlimit(RLIMIT_CPU, &rl);
 104     assert(r >= 0);
 105
 106     rl.rlim_cur = n;
 107     r = setrlimit(RLIMIT_CPU, &rl);
 108     assert(r >= 0);
 109 }
 110
 111 /* A simple, thread-safe puts() work-alike */
 112 static void write_err(const char *p) {
 113     pa_loop_write(2, p, strlen(p));
 114 }
 115
 116 /* The signal handler, called on every SIGXCPU */
 117 static void signal_handler(int sig) {
 118     assert(sig == SIGXCPU);
 119
 120     if (phase == PHASE_IDLE) {
 121         time_t now;
 122
 123 #ifdef PRINT_CPU_LOAD
 124         char t[256];
 125 #endif
 126
 127         time(&now);
 128
 129 #ifdef PRINT_CPU_LOAD
 130         snprintf(t, sizeof(t), "Using %0.1f%% CPU\n", (double)CPUTIME_INTERVAL_SOFT/(now-last_time)*100);
 131         write_err(t);
 132 #endif
 133
 134         if (CPUTIME_INTERVAL_SOFT >= ((now-last_time)*(double)CPUTIME_PERCENT/100)) {
 135             static const char c = 'X';
 136
 137             write_err("Soft CPU time limit exhausted, terminating.\n");
 138
 139             /* Try a soft cleanup */
 140             write(the_pipe[1], &c, sizeof(c));
 141             phase = PHASE_SOFT;
 142             reset_cpu_time(CPUTIME_INTERVAL_HARD);
 143
 144         } else {
 145
 146             /* Everything's fine */
 147             reset_cpu_time(CPUTIME_INTERVAL_SOFT);
 148             last_time = now;
 149         }
 150
 151     } else if (phase == PHASE_SOFT) {
 152         write_err("Hard CPU time limit exhausted, terminating forcibly.\n");
 153         _exit(1); /* Forced exit */
 154     }
 155 }
 156
 157 /* Callback for IO events on the FIFO */
 158 static void callback(pa_mainloop_api*m, pa_io_event*e, int fd, pa_io_event_flags f, void *userdata) {
 159     char c;
 160     assert(m && e && f == PA_IO_EVENT_INPUT && e == io_event && fd == the_pipe[0]);
 161     read(the_pipe[0], &c, sizeof(c));
 162     m->quit(m, 1); /* Quit the main loop */
 163 }
 164
 165 /* Initializes CPU load limiter */
 166 int pa_cpu_limit_init(pa_mainloop_api *m) {
 167     struct sigaction sa;
 168     assert(m && !api && !io_event && the_pipe[0] == -1 && the_pipe[1] == -1 && !installed);
 169
 170     time(&last_time);
 171
 172     /* Prepare the main loop pipe */
 173     if (pipe(the_pipe) < 0) {
 174         pa_log(__FILE__": pipe() failed: %s", pa_cstrerror(errno));
 175         return -1;
 176     }
 177
 178     pa_make_nonblock_fd(the_pipe[0]);
 179     pa_make_nonblock_fd(the_pipe[1]);
 180     pa_fd_set_cloexec(the_pipe[0], 1);
 181     pa_fd_set_cloexec(the_pipe[1], 1);
 182
 183     api = m;
 184     io_event = api->io_new(m, the_pipe[0], PA_IO_EVENT_INPUT, callback, NULL);
 185
 186     phase = PHASE_IDLE;
 187
 188     /* Install signal handler for SIGXCPU */
 189     memset(&sa, 0, sizeof(sa));
 190     sa.sa_handler = signal_handler;
 191     sigemptyset(&sa.sa_mask);
 192     sa.sa_flags = SA_RESTART;
 193
 194     if (sigaction(SIGXCPU, &sa, &sigaction_prev) < 0) {
 195         pa_cpu_limit_done();
 196         return -1;
 197     }
 198
 199     installed = 1;
 200
 201     reset_cpu_time(CPUTIME_INTERVAL_SOFT);
 202
 203     return 0;
 204 }
 205
 206 /* Shutdown CPU load limiter */
 207 void pa_cpu_limit_done(void) {
 208     int r;
 209
 210     if (io_event) {
 211         assert(api);
 212         api->io_free(io_event);
 213         io_event = NULL;
 214         api = NULL;
 215     }
 216
 217     if (the_pipe[0] >= 0)
 218         close(the_pipe[0]);
 219     if (the_pipe[1] >= 0)
 220         close(the_pipe[1]);
 221     the_pipe[0] = the_pipe[1] = -1;
 222
 223     if (installed) {
 224         r = sigaction(SIGXCPU, &sigaction_prev, NULL);
 225         assert(r >= 0);
 226         installed = 0;
 227     }
 228 }
 229
 230 #else /* HAVE_SIGXCPU */
 231
 232 int pa_cpu_limit_init(PA_GCC_UNUSED pa_mainloop_api *m) {
 233     return 0;
 234 }
 235
 236 void pa_cpu_limit_done(void) {
 237 }
 238
 239 #endif