code.delx.au - pulseaudio/blob - src/daemon/cpulimit.c

   1 /* $Id$ */
   2
   3 /***
   4   This file is part of PulseAudio.
   5
   6   PulseAudio 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   PulseAudio 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 PulseAudio; 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 <pulse/error.h>
  27
  28 #include <pulsecore/core-util.h>
  29 #include <pulsecore/core-error.h>
  30 #include <pulsecore/log.h>
  31
  32 #include "cpulimit.h"
  33
  34 #ifdef HAVE_SIGXCPU
  35
  36 #include <errno.h>
  37 #include <stdio.h>
  38 #include <string.h>
  39 #include <assert.h>
  40 #include <sys/time.h>
  41 #include <unistd.h>
  42 #include <signal.h>
  43
  44 #ifdef HAVE_SYS_RESOURCE_H
  45 #include <sys/resource.h>
  46 #endif
  47
  48 /* This module implements a watchdog that makes sure that the current
  49  * process doesn't consume more than 70% CPU time for 10 seconds. This
  50  * is very useful when using SCHED_FIFO scheduling which effectively
  51  * disables multitasking. */
  52
  53 /* Method of operation: Using SIGXCPU a signal handler is called every
  54  * 10s process CPU time. That function checks if less than 14s system
  55  * time have passed. In that case, it tries to contact the main event
  56  * loop through a pipe. After two additional seconds it is checked
  57  * whether the main event loop contact was successful. If not, the
  58  * program is terminated forcibly. */
  59
  60 /* Utilize this much CPU time at maximum */
  61 #define CPUTIME_PERCENT 70
  62
  63 /* Check every 10s */
  64 #define CPUTIME_INTERVAL_SOFT (10)
  65
  66 /* Recheck after 5s */
  67 #define CPUTIME_INTERVAL_HARD (5)
  68
  69 /* Time of the last CPU load check */
  70 static time_t last_time = 0;
  71
  72 /* Pipe for communicating with the main loop */
  73 static int the_pipe[2] = {-1, -1};
  74
  75 /* Main event loop and IO event for the FIFO */
  76 static pa_mainloop_api *api = NULL;
  77 static pa_io_event *io_event = NULL;
  78
  79 /* Saved sigaction struct for SIGXCPU */
  80 static struct sigaction sigaction_prev;
  81
  82 /* Nonzero after pa_cpu_limit_init() */
  83 static int installed = 0;
  84
  85 /* The current state of operation */
  86 static enum  {
  87     PHASE_IDLE,   /* Normal state */
  88     PHASE_SOFT    /* After CPU overload has been detected */
  89 } phase = PHASE_IDLE;
  90
  91 /* Reset the SIGXCPU timer to the next t seconds */
  92 static void reset_cpu_time(int t) {
  93     int r;
  94     long n;
  95     struct rlimit rl;
  96     struct rusage ru;
  97
  98     /* Get the current CPU time of the current process */
  99     r = getrusage(RUSAGE_SELF, &ru);
 100     assert(r >= 0);
 101
 102     n = ru.ru_utime.tv_sec + ru.ru_stime.tv_sec + t;
 103
 104     r = getrlimit(RLIMIT_CPU, &rl);
 105     assert(r >= 0);
 106
 107     rl.rlim_cur = n;
 108     r = setrlimit(RLIMIT_CPU, &rl);
 109     assert(r >= 0);
 110 }
 111
 112 /* A simple, thread-safe puts() work-alike */
 113 static void write_err(const char *p) {
 114     pa_loop_write(2, p, strlen(p));
 115 }
 116
 117 /* The signal handler, called on every SIGXCPU */
 118 static void signal_handler(int sig) {
 119     assert(sig == SIGXCPU);
 120
 121     if (phase == PHASE_IDLE) {
 122         time_t now;
 123
 124 #ifdef PRINT_CPU_LOAD
 125         char t[256];
 126 #endif
 127
 128         time(&now);
 129
 130 #ifdef PRINT_CPU_LOAD
 131         snprintf(t, sizeof(t), "Using %0.1f%% CPU\n", (double)CPUTIME_INTERVAL_SOFT/(now-last_time)*100);
 132         write_err(t);
 133 #endif
 134
 135         if (CPUTIME_INTERVAL_SOFT >= ((now-last_time)*(double)CPUTIME_PERCENT/100)) {
 136             static const char c = 'X';
 137
 138             write_err("Soft CPU time limit exhausted, terminating.\n");
 139
 140             /* Try a soft cleanup */
 141             write(the_pipe[1], &c, sizeof(c));
 142             phase = PHASE_SOFT;
 143             reset_cpu_time(CPUTIME_INTERVAL_HARD);
 144
 145         } else {
 146
 147             /* Everything's fine */
 148             reset_cpu_time(CPUTIME_INTERVAL_SOFT);
 149             last_time = now;
 150         }
 151
 152     } else if (phase == PHASE_SOFT) {
 153         write_err("Hard CPU time limit exhausted, terminating forcibly.\n");
 154         _exit(1); /* Forced exit */
 155     }
 156 }
 157
 158 /* Callback for IO events on the FIFO */
 159 static void callback(pa_mainloop_api*m, pa_io_event*e, int fd, pa_io_event_flags_t f, void *userdata) {
 160     char c;
 161     assert(m && e && f == PA_IO_EVENT_INPUT && e == io_event && fd == the_pipe[0]);
 162     read(the_pipe[0], &c, sizeof(c));
 163     m->quit(m, 1); /* Quit the main loop */
 164 }
 165
 166 /* Initializes CPU load limiter */
 167 int pa_cpu_limit_init(pa_mainloop_api *m) {
 168     struct sigaction sa;
 169     assert(m && !api && !io_event && the_pipe[0] == -1 && the_pipe[1] == -1 && !installed);
 170
 171     time(&last_time);
 172
 173     /* Prepare the main loop pipe */
 174     if (pipe(the_pipe) < 0) {
 175         pa_log(__FILE__": pipe() failed: %s", pa_cstrerror(errno));
 176         return -1;
 177     }
 178
 179     pa_make_nonblock_fd(the_pipe[0]);
 180     pa_make_nonblock_fd(the_pipe[1]);
 181     pa_fd_set_cloexec(the_pipe[0], 1);
 182     pa_fd_set_cloexec(the_pipe[1], 1);
 183
 184     api = m;
 185     io_event = api->io_new(m, the_pipe[0], PA_IO_EVENT_INPUT, callback, NULL);
 186
 187     phase = PHASE_IDLE;
 188
 189     /* Install signal handler for SIGXCPU */
 190     memset(&sa, 0, sizeof(sa));
 191     sa.sa_handler = signal_handler;
 192     sigemptyset(&sa.sa_mask);
 193     sa.sa_flags = SA_RESTART;
 194
 195     if (sigaction(SIGXCPU, &sa, &sigaction_prev) < 0) {
 196         pa_cpu_limit_done();
 197         return -1;
 198     }
 199
 200     installed = 1;
 201
 202     reset_cpu_time(CPUTIME_INTERVAL_SOFT);
 203
 204     return 0;
 205 }
 206
 207 /* Shutdown CPU load limiter */
 208 void pa_cpu_limit_done(void) {
 209     int r;
 210
 211     if (io_event) {
 212         assert(api);
 213         api->io_free(io_event);
 214         io_event = NULL;
 215         api = NULL;
 216     }
 217
 218     if (the_pipe[0] >= 0)
 219         close(the_pipe[0]);
 220     if (the_pipe[1] >= 0)
 221         close(the_pipe[1]);
 222     the_pipe[0] = the_pipe[1] = -1;
 223
 224     if (installed) {
 225         r = sigaction(SIGXCPU, &sigaction_prev, NULL);
 226         assert(r >= 0);
 227         installed = 0;
 228     }
 229 }
 230
 231 #else /* HAVE_SIGXCPU */
 232
 233 int pa_cpu_limit_init(PA_GCC_UNUSED pa_mainloop_api *m) {
 234     return 0;
 235 }
 236
 237 void pa_cpu_limit_done(void) {
 238 }
 239
 240 #endif