Hi Darren,
On 02/09, Darren Hart wrote:
>
> I will prepare the test that Peter suggested so we have something to
> test with now as well as run for regressions over time.
Just in case, I already wrote the stupid test-case:
#include <stdio.h>
#include <unistd.h>
#include <signal.h>
#include <sys/syscall.h>
#include <sys/wait.h>
#include <sys/mman.h>
#include <assert.h>
#define FUTEX_LOCK_PI 6
struct robust_list {
struct robust_list *next;
};
struct robust_list_head {
struct robust_list list;
long futex_offset;
struct robust_list *list_op_pending;
};
int main(void)
{
int *mutex = mmap(NULL, 4, PROT_READ|PROT_WRITE,
MAP_ANONYMOUS|MAP_SHARED, -1,0);
assert((void *)mutex != MAP_FAILED);
for (;;) {
int err, pid = fork();
if (!pid) {
struct robust_list_head head;
head.list.next = &head.list;
head.futex_offset = 0;
head.list_op_pending = (void *)mutex + 1;
assert(syscall(__NR_set_robust_list, &head,
sizeof(head)) == 0);
kill(getpid(), SIGSTOP);
_exit(0);
}
assert(waitpid(-1, NULL, WSTOPPED) == pid);
*mutex = pid;
kill(pid, SIGKILL);
err = syscall(__NR_futex, mutex, FUTEX_LOCK_PI, 0,0,0);
assert(wait(NULL) == pid);
if (err) {
printf("err=%d %m\n", err);
kill(0, SIGKILL);
}
}
return 0;
}
it needs ~20 secs to fail on my machine. Probably it can be improved.
> Hrm, if we cleared the TID mask, and the pi chain is empty, can we not
> clear the waiters?
In this case the waiter should take care, I guess.
OK. I'll try to make at least the 1st fix today (EXITING -> EXITPIDONE
livelock).
Oleg.
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