POSIX signal handling

[Sérgio Santos]

Hello all, 

I'm using rtems 4.8.1, target is i386 (single core, with FC9), using bsp's between pc386 and pc686 and the RTEMS makefile templates.

I have been trying to port a Linux based application to RTEMS and found at some point I couldn't get POSIX signal handlers (set with sigaction) to ever execute. From what I've read in rtems-users and user docs, no problems should arise from using POSIX asynchronous signal handling in RTEMS, so my guess is I'm making some naïve mistake on code or configuration... 

Also, searching on the list, came across a similar problem, but this was a unique case and a long while ago: 
http://www.rtems.com/ml/rtems-users/2002/september/msg00015.html
Unfortunately that thread was not conclusive.

After a few other tests I've got down to a simple test application (see below), similar to the code in the post I mentioned above: a thread sets sigaction and just does alarm(1), sleep(3) in a cycle. Alike the other tests, in RTEMS the handler never gets to run (although the signal (SIGALRM) is seen pending); in Linux all tests will work.

POSIX was enabled in the build configuration: 
../../../rtems-4.8.1/c/configure --prefix=/opt/rtems-4.8 --host=i386-rtems4.8 --build=i686-pc-linux-gnu --target=i386-rtems4.8 --enable-posix --disable-itron --enable-networking --enable-cxx --enable-rtems-debug --enable-rdbg --enable-rtemsbsp=pc386 --with-target-subdir=i386-rtems4.8 --exec-prefix=/opt/rtems-4.8/i386-rtems4.8 --includedir=/opt/rtems-4.8/i386-rtems4.8/include --cache-file=/dev/null --srcdir=../../../rtems-4.8.1/c

I post below the src for the simple test, having the RTEMS definitions in the end.


Thanks in advance for your help!

Sérgio Santos


--------------


#include <signal.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>

#include <bsp.h>

void sig_handler(int sig){
	switch(sig){
	case SIGALRM:
		printf("HANDLER: caught SIGALRM\n");
		break;
	default:
		printf("Received unexpected signal (%d)\nBye!", sig);
		exit(1);
	}
}

void sig_init(){

	int rc;
	sigset_t 			sigset;
	struct sigaction 	sigact;

	rc = sigemptyset(&sigset);
	if (rc != 0) {
		printf("Can't empty set\n");exit(1);
	}

	sigact.sa_mask 		= sigset;
	sigact.sa_flags 	= 0;
	sigact.sa_handler 	= &sig_handler;

	rc = sigaction(SIGALRM, &sigact, NULL);
	if (rc != 0) {
		printf("Can't install handler\n"); exit(1);
	}
}

void *POSIX_Init(void *arg){

	int rc = 0;
	sigset_t pendingset;

	sig_init();

	rc = sigemptyset(&pendingset);
	if (rc != 0) {
		printf("Can't empty set\n");exit(1);
	}

	while(1){
		alarm(1);
		sleep(3);
		sigpending(&pendingset);
		printf("%s\n\n", ( sigismember(&pendingset, SIGALRM) ?
				"SIGALRM is pending" : "SIGALRM not pending" ));
	}
	return 0;
}

#define CONFIGURE_MAXIMUM_POSIX_THREADS 10
#define CONFIGURE_MAXIMUM_POSIX_MUTEXES 10
#define CONFIGURE_MAXIMUM_POSIX_TIMERS  10
#define CONFIGURE_MAXIMUM_POSIX_QUEUED_SIGNALS 40

#define CONFIGURE_APPLICATION_NEEDS_CLOCK_DRIVER
#define CONFIGURE_APPLICATION_NEEDS_TIMER_DRIVER
#define CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER
#define CONFIGURE_POSIX_INIT_THREAD_TABLE
#define CONFIGURE_INIT

// EOF
----