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

   1 /***
   2   This file is part of PulseAudio.
   3
   4   Copyright 2004-2006 Lennart Poettering
   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 2.1 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/rtclock.h>
  27 #include <pulse/timeval.h>
  28
  29 #include <pulsecore/core-util.h>
  30 #include <pulsecore/core-error.h>
  31 #include <pulsecore/log.h>
  32 #include <pulsecore/macro.h>
  33
  34 #include "cpulimit.h"
  35
  36 #ifdef HAVE_SIGXCPU
  37
  38 #include <errno.h>
  39 #include <stdio.h>
  40 #include <string.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 pa_usec_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 bool installed = false;
  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     long n;
  94     struct rlimit rl;
  95     struct rusage ru;
  96
  97     /* Get the current CPU time of the current process */
  98     pa_assert_se(getrusage(RUSAGE_SELF, &ru) >= 0);
  99
 100     n = ru.ru_utime.tv_sec + ru.ru_stime.tv_sec + t;
 101     pa_assert_se(getrlimit(RLIMIT_CPU, &rl) >= 0);
 102
 103     rl.rlim_cur = (rlim_t) n;
 104     pa_assert_se(setrlimit(RLIMIT_CPU, &rl) >= 0);
 105 }
 106
 107 /* A simple, thread-safe puts() work-alike */
 108 static void write_err(const char *p) {
 109     pa_loop_write(2, p, strlen(p), NULL);
 110 }
 111
 112 /* The signal handler, called on every SIGXCPU */
 113 static void signal_handler(int sig) {
 114     int saved_errno;
 115
 116     saved_errno = errno;
 117     pa_assert(sig == SIGXCPU);
 118
 119     if (phase == PHASE_IDLE) {
 120         pa_usec_t now, elapsed;
 121
 122 #ifdef PRINT_CPU_LOAD
 123         char t[256];
 124 #endif
 125
 126         now = pa_rtclock_now();
 127         elapsed = now - last_time;
 128
 129 #ifdef PRINT_CPU_LOAD
 130         pa_snprintf(t, sizeof(t), "Using %0.1f%% CPU\n", ((double) CPUTIME_INTERVAL_SOFT * (double) PA_USEC_PER_SEC) / (double) elapsed * 100.0);
 131         write_err(t);
 132 #endif
 133
 134         if (((double) CPUTIME_INTERVAL_SOFT * (double) PA_USEC_PER_SEC) >= ((double) elapsed * (double) CPUTIME_PERCENT / 100.0)) {
 135             static const char c = 'X';
 136
 137             write_err("Soft CPU time limit exhausted, terminating.\n");
 138
 139             /* Try a soft cleanup */
 140             (void) pa_write(the_pipe[1], &c, sizeof(c), NULL);
 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         abort(); /* Forced exit */
 154     }
 155
 156     errno = saved_errno;
 157 }
 158
 159 /* Callback for IO events on the FIFO */
 160 static void callback(pa_mainloop_api*m, pa_io_event*e, int fd, pa_io_event_flags_t f, void *userdata) {
 161     char c;
 162     pa_assert(m);
 163     pa_assert(e);
 164     pa_assert(f == PA_IO_EVENT_INPUT);
 165     pa_assert(e == io_event);
 166     pa_assert(fd == the_pipe[0]);
 167
 168     pa_log("Received request to terminate due to CPU overload.");
 169
 170     (void) pa_read(the_pipe[0], &c, sizeof(c), NULL);
 171     m->quit(m, 1); /* Quit the main loop */
 172 }
 173
 174 /* Initializes CPU load limiter */
 175 int pa_cpu_limit_init(pa_mainloop_api *m) {
 176     struct sigaction sa;
 177
 178     pa_assert(m);
 179     pa_assert(!api);
 180     pa_assert(!io_event);
 181     pa_assert(the_pipe[0] == -1);
 182     pa_assert(the_pipe[1] == -1);
 183     pa_assert(!installed);
 184
 185     last_time = pa_rtclock_now();
 186
 187     /* Prepare the main loop pipe */
 188     if (pa_pipe_cloexec(the_pipe) < 0) {
 189         pa_log("pipe() failed: %s", pa_cstrerror(errno));
 190         return -1;
 191     }
 192
 193     pa_make_fd_nonblock(the_pipe[0]);
 194     pa_make_fd_nonblock(the_pipe[1]);
 195
 196     api = m;
 197     io_event = api->io_new(m, the_pipe[0], PA_IO_EVENT_INPUT, callback, NULL);
 198
 199     phase = PHASE_IDLE;
 200
 201     /* Install signal handler for SIGXCPU */
 202     memset(&sa, 0, sizeof(sa));
 203     sa.sa_handler = signal_handler;
 204     sigemptyset(&sa.sa_mask);
 205     sa.sa_flags = SA_RESTART;
 206
 207     if (sigaction(SIGXCPU, &sa, &sigaction_prev) < 0) {
 208         pa_cpu_limit_done();
 209         return -1;
 210     }
 211
 212     installed = true;
 213
 214     reset_cpu_time(CPUTIME_INTERVAL_SOFT);
 215
 216     return 0;
 217 }
 218
 219 /* Shutdown CPU load limiter */
 220 void pa_cpu_limit_done(void) {
 221
 222     if (io_event) {
 223         pa_assert(api);
 224         api->io_free(io_event);
 225         io_event = NULL;
 226         api = NULL;
 227     }
 228
 229     pa_close_pipe(the_pipe);
 230
 231     if (installed) {
 232         pa_assert_se(sigaction(SIGXCPU, &sigaction_prev, NULL) >= 0);
 233         installed = false;
 234     }
 235 }
 236
 237 #else /* HAVE_SIGXCPU */
 238
 239 int pa_cpu_limit_init(pa_mainloop_api *m) {
 240     return 0;
 241 }
 242
 243 void pa_cpu_limit_done(void) {
 244 }
 245
 246 #endif