Breakpoint suspend set doesn't seem to work

[simark]

I don't know if I am not using it right, or if it's buggy, but here is how it goes. I use the following test case:

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

static pthread_barrier_t barrier;

void *t1_func(void *arg) {
    int i;

    pthread_barrier_wait (&barrier);

    for (i = 0; i < 100; i++) {
        sleep (1);
    }

    return NULL;
}

void *t2_func(void *arg) {
    int i;

    pthread_barrier_wait (&barrier);

    for (i = 0; i < 100; i++) {
        sleep (1);
    }

    return NULL;
}

void all_threads_started (void)
{
}

int main(int argc, char **argv) {
    pthread_t t1, t2;

    pthread_barrier_init (&barrier, NULL, 3);

    pthread_create(&t1, NULL, t1_func, NULL);
    pthread_create(&t2, NULL, t2_func, NULL);

    pthread_barrier_wait (&barrier);

    all_threads_started ();

    pthread_join(t1, NULL);
    pthread_join(t2, NULL);

    return 0;
}

I start gdb with:

$ ./gdb -nx threads -ex "b all_threads_started" -ex  r

Once there, I want to set a breakpoint in the thread 1's (t1.2) code that will only interrupt thread 2 (t1.3).

(gdb) itfocus tt1.2 break -suspend tt1.3 threads.c:12
Breakpoint 2 at 0x40076c: file threads.c, line 12.
(gdb) i b
Num     Type           Disp Enb Address            What
1       breakpoint     keep y   0x00000000004007cf in all_threads_started at threads.c:32
    trigger only in: at1.1
    suspend all of: at*.*
    breakpoint already hit 1 time
2       breakpoint     keep y   0x000000000040076c in t1_func at threads.c:12
    trigger only in: tt1.2
    suspend all of: tt1.3

So far this looks good, breakpoint 2 will only get triggered by thread 1.2 and will only suspend thread 1.3. I continue:

(gdb) c
Continuing.
[Switching to Thread 0x7ffff77f6700 (LWP 31988)]

Breakpoint 2, t1_func (arg=0x0) at threads.c:12
12          sleep (1);
(gdb) i th
  Id   Target Id         Frame 
  1.1  Thread 0x7ffff7fc5740 (LWP 31984) "threads" (running)
* 1.2  Thread 0x7ffff77f6700 (LWP 31988) "threads" t1_func (arg=0x0) at threads.c:12
  1.3  Thread 0x7ffff6ff5700 (LWP 31989) "threads" 0x00007ffff78b7dfd in nanosleep ()
   from /lib/x86_64-linux-gnu/libc.so.6

Thread 1.3 is interrupted somewhere in its sleep, which is expected, but thread 1.2 was stopped as well, which is unexpected.

If I try in non-stop instead:

$ ./gdb -nx threads -ex "set non-stop on" -ex "b all_threads_started" -ex  r

depending on whether I stop the threads before inserting the breakpoints, I get two different results:

(gdb) i th
  Id   Target Id         Frame 
* 1.1  Thread 0x7ffff7fc5740 (LWP 32591) "threads" all_threads_started () at threads.c:32
  1.2  Thread 0x7ffff77f6700 (LWP 32595) "threads" (running)
  1.3  Thread 0x7ffff6ff5700 (LWP 32596) "threads" (running)
(gdb) itfocus tt1.2 break -suspend tt1.3 threads.c:12
Breakpoint 2 at 0x40076c: file threads.c, line 12.
(gdb) 
Breakpoint 2, t1_func (arg=0x0) at threads.c:12
12          sleep (1);
i th
  Id   Target Id         Frame 
* 1.1  Thread 0x7ffff7fc5740 (LWP 32591) "threads" all_threads_started () at threads.c:32
  1.2  Thread 0x7ffff77f6700 (LWP 32595) "threads" t1_func (arg=0x0) at threads.c:12
  1.3  Thread 0x7ffff6ff5700 (LWP 32596) "threads" (running)

t1.2 was stopped, whereas we would have expected thread 1.3 to stop. Thread 1.1 is still stopped, which is fine because I haven't told it to resume.

And:

(gdb) interrupt -a
(gdb) 
[Thread 0x7ffff77f6700 (LWP 401)] #2 stopped.
0x00007ffff78b7dfd in nanosleep () from /lib/x86_64-linux-gnu/libc.so.6

[Thread 0x7ffff6ff5700 (LWP 402)] #3 stopped.
0x00007ffff78b7dfd in nanosleep () from /lib/x86_64-linux-gnu/libc.so.6
i th
  Id   Target Id         Frame 
* 1.1  Thread 0x7ffff7fc5740 (LWP 397) "threads" all_threads_started () at threads.c:32
  1.2  Thread 0x7ffff77f6700 (LWP 401) "threads" 0x00007ffff78b7dfd in nanosleep ()
   from /lib/x86_64-linux-gnu/libc.so.6
  1.3  Thread 0x7ffff6ff5700 (LWP 402) "threads" 0x00007ffff78b7dfd in nanosleep ()
   from /lib/x86_64-linux-gnu/libc.so.6
(gdb) itfocus tt1.2 break -suspend tt1.3 threads.c:12
Breakpoint 2 at 0x40076c: file threads.c, line 12.
(gdb) c -a &
Continuing.

We would expect a stop of thread 1.3, but nothing stops. The info breakpoint still shows the correct information:

(gdb) i b
Num     Type           Disp Enb Address            What
1       breakpoint     keep y   0x00000000004007cf in all_threads_started at threads.c:32
    trigger only in: at1.1
    suspend all of: 
    breakpoint already hit 1 time
2       breakpoint     keep y   0x000000000040076c in t1_func at threads.c:12
    trigger only in: tt1.2
    suspend all of: tt1.3