Re: gdbserver signals interfere with {next,step{,i}}

[Jon Ringle <jon@ringle.org>]

[-- Attachment #1: Type: text/plain, Size: 955 bytes --]

Daniel Jacobowitz wrote:
> On Mon, Mar 05, 2007 at 03:05:34PM -0500, Jon Ringle wrote:
>   
>> Hello,
>>
>> I have an application that uses SIGUSR1 to receive timer interrupts. 
>> I've done 'handle SIGUSR1 nostop noprint' to avoid gdb from stopping on 
>> SIGUSR1.
>> I've found that when debugging this application using gdbserver, that I 
>> can't use next, nexti, step, or stepi. When I use one of these commands, 
>> the application usually just continues without stopping at the next 
>> line/instruction.
>>
>> If I use a native gdb on the target the problem does not occur.
>> If I disable my app from generating the SIGUSR1 and use gdbserver, the 
>> problem also goes away.
>>     
>
> I haven't seen this problem before.  Can you make a small test case
> which demonstrates the problem, maybe?
>
>   
Attached is a test case. <cid:part1.03040401.03010207@ringle.org>
> What target are you using?
>
>   
My target is armeb-linux.

Thanks,

Jon


[-- Attachment #2: gdbsignal-test.c --]
[-- Type: text/plain, Size: 2190 bytes --]

#include <stdio.h>
#include <pthread.h>
#include <signal.h>

static void signal_handler (int signo);
static timer_t   timer_id       = -1;
#define ERROR (-1)

int i = 0;
void signal_handler(int signo)
{
	// Perform a use-less task
	i++;
}

void init_signals (void)
{
	struct sigaction  sig_act;
	struct sigevent   evp;
    	struct itimerspec   ttime;
    
	/* initialize sig_act */
	sig_act.sa_handler = (void*)signal_handler;
	sig_act.sa_flags   = 0;
	sigemptyset(&sig_act.sa_mask);

	sigaction(SIGUSR1, &sig_act, 0);
	
	evp.sigev_value.sival_int = 0;
	evp.sigev_signo = SIGUSR1;
        timer_create (CLOCK_REALTIME, &evp, &timer_id);

	ttime.it_value.tv_sec     = 0;          /* 0  S */
	ttime.it_value.tv_nsec    = 20000000;   /* 20mS */
	ttime.it_interval.tv_sec  = 0;          /* 0  S */
	ttime.it_interval.tv_nsec = 20000000;   /* 20mS */
	
	/* fire off the periodic timer - relative mode = 0 */
	timer_settime(timer_id, 0, &ttime, NULL);
}

static int get_input(char *buffer, int size)
{
	char    c;
	int     status, counter, dummy;
	
	counter= 0;
	c      = 0;
	status = 0;
	
	while (c != '\r')
	{
		dummy = getc(stdin);
		c = (char)dummy;
		
		if ((dummy != EOF) && (dummy != 0)) {
			if ( isprint(c) && (counter < size-1) )  {
				buffer[counter++] = c;
			} else if ((c == '\r') || (c == '\n')) {
				/* return user's str length - while loop will terminate */
				status = counter;
				
				c = '\r';
			} else  {
				; /* Ignore any other characters */
			}
			
		} else {
			memset (buffer, 0, size);
			
			counter = 0;
			if (dummy == 0)
				printf ("\nreceived NULL!\n");
			
			else
				printf ("\n\nGot EOF!\n");
			sleep(10);
			c      = '\r';
			status = ERROR;
		}
	}
	buffer[counter] = 0;
	return status;
}

void* thread(void* dummy)
{
	init_signals();

	while (1)
		;
	return NULL;
}

int main(int argc, char* argv[])
{
	pthread_t tid;
	pthread_create(&tid, NULL, &thread, NULL);
	while (1)
	{
		char buffer[200];
		printf ("Prompt %d> ", i);
		get_input(buffer, sizeof(buffer));

		// Give ourselves something to next...
		printf("Got "); // <<<<<<<<<<<<< Put breakpoint here 
		printf("'%s'", buffer);
		printf("\n");
	}
	pthread_join(tid,NULL);
	return 0;
}