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mod_shell_stream: fix file_open() blocking playback until child exits #3104

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mod_shell_stream: fix file_open() blocking playback until child exits #3104

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36 changes: 34 additions & 2 deletions src/mod/formats/mod_shell_stream/mod_shell_stream.c
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Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,7 @@
*/
#include <switch.h>
#include <sys/wait.h>
#include <signal.h>

#define MY_BUF_LEN 1024 * 32
#define MY_BLOCK_SIZE MY_BUF_LEN
Expand Down Expand Up @@ -137,7 +138,13 @@ static switch_status_t shell_stream_file_open(switch_file_handle_t *handle, cons
switch_cond_next();
}

wait(&(context->pid));
/* NOTE: we intentionally do NOT wait() for the child here.
Doing so blocks file_open() until the child process fully
exits, which means FreeSWITCH can't start calling
file_read() (i.e. can't start playing anything) until the
ENTIRE external command has finished running - defeating
the purpose of the background buffering thread above.
The child is instead reaped in shell_stream_file_close(). */

goto end;
} else { /* child */
Expand Down Expand Up @@ -184,6 +191,31 @@ static switch_status_t shell_stream_file_close(switch_file_handle_t *handle)
switch_thread_rwlock_wrlock(context->rwlock);
switch_thread_rwlock_unlock(context->rwlock);

/* Reap the child process here instead of in file_open(). Closing
fds[0] above closes the read end of the pipe, so if the child is
still writing (e.g. playback was stopped mid-stream), its next
write will fail (EPIPE/SIGPIPE) and it should exit on its own
shortly. Give it a brief grace period, then force-kill as a
safety net so we never block indefinitely or leak a process. */
if (context->pid > 0) {
int status = 0;
pid_t wp;
int tries = 0;

while ((wp = waitpid(context->pid, &status, WNOHANG)) == 0 && tries < 100) {
switch_yield(10000); /* 10ms; ~1s total grace period */
tries++;
}

if (wp == 0) {
switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_WARNING,
"shell_stream child pid %d did not exit after stream close, killing it\n",
(int) context->pid);
kill(context->pid, SIGKILL);
waitpid(context->pid, &status, 0);
}
}

return SWITCH_STATUS_SUCCESS;
}

Expand Down Expand Up @@ -234,4 +266,4 @@ SWITCH_MODULE_LOAD_FUNCTION(mod_shell_stream_load)
* End:
* For VIM:
* vim:set softtabstop=4 shiftwidth=4 tabstop=4 noet:
*/
*/