Hi All,
I'm trying to get my head around handling signals in a threaded app.
However, I keep just getting a stack backtrace written to stderr. As far
as I can tell my signal handler never gets a look in.
In main(), before any other threads are created, I have this code to
block all signals and then create the signal-catching thread.
/* Block all signals */
sigfillset(&signal_set);
pthread_sigmask(SIG_BLOCK, &signal_set, NULL);
/* Signal handler thread */
if (pthread_create(&app.control_threads.tid2, NULL,
&BT_Signal_Catcher, "Signal Thread"))
{
BT_Log(log_CRITICAL, "Unable to create Signal Thread - nasty!");
abort();
}
The signal-catching thread, which claims the signals, is:
#define NO_SIGNAL -1
int signal_handled = NO_SIGNAL;
pthread_mutex_t signal_mutex = PTHREAD_MUTEX_INITIALIZER;
void *BT_Signal_Catcher(void *vptr_args)
{
sigset_t signal_set;
int sig;
UNUSED(vptr_args);
BugF("Function:BT_Signal_Catcher");
/* "go" gets set to false at end of BT_Routine_Exit */
while(app.control_threads.go)
{
/* Wait for any signal */
sigfillset(&signal_set);
Bug("SigThrd: going to sleep...");
sigwait(&signal_set, &sig);
Bug("SigThrd: woken up!");
/* Set value, which is tested in null handler */
pthread_mutex_lock(&signal_mutex);
signal_handled = sig;
pthread_mutex_unlock(&signal_mutex);
}
BugF("Function(exit):BT_Signal_Catcher");
pthread_exit(NULL);
}
Finally, at the beginning of the wimp polling loop I've got:
BOOL BT_Null_Handler(event_pollblock *event, void *reference)
{
UNUSED(event);
UNUSED(reference);
pthread_yield();
if (signal_handled != NO_SIGNAL)
{
Debug_Printf("arglglgey bargle %s", strsignal(signal_handled));
pthread_mutex_lock(&signal_mutex);
signal_handled = NO_SIGNAL;
pthread_mutex_unlock(&signal_mutex);
abort();
}
...
Everything seems to go OK, and the signal thread goes to sleep as
expected, but it doesn't appear to wake up when I generate a synchronous
signal. What am I doing wrong?
Thanks a lot,
Adam
--
Adam Richardson Carpe Diem
http://www.snowstone.org.uk/riscos/
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