Eric,
I am sick today and can't read the code, but I feel this patch is not
right ... please correct me.
So, iiuc when posix_cpu_timer_create() is called and CPUCLOCK_PERTHREAD
is false we roughly have
task = pid_task(pid, PIDTYPE_TGID); // lookup_task()
/* WINDOW */
timer->it.cpu.pid = = get_task_pid(task, PIDTYPE_TGID) // posix_cpu_timer_create()
Now suppose that we race with mt-exec and this "task" is the old leader;
it can be release_task()'ed in the WINDOW above and then get_task_pid()
will return NULL.
That is why I suggested to change lookup_task() to return "struct pid*"
to eliminate the pid -> task -> pid transition.
Apart from the same_thread_group() check for the "thread" case we do not
need task_struct at all, lookup_task() can do
if (thread) {
p = pid_task(pid, PIDTYPE_PID);
if (p && !same_thread_group(p, current))
pid = NULL;
} else {
... gettime check ...
if (!pid_has_task(pid, PIDTYPE_TGID))
pid = NULL;
}
return pid;
No?
Oleg.
