posix-timers: use "struct pid*" instead of "struct task_struct*"
Impact: restructure, clean up code k_itimer holds the ref to the ->it_process until sys_timer_delete(). This allows to pin up to RLIMIT_SIGPENDING dead task_struct's. Change the code to use "struct pid *" instead. The patch doesn't kill ->it_process, it places ->it_pid into the union. ->it_process is still used by do_cpu_nanosleep() as before. It would be trivial to change the nanosleep code as well, but since it uses it_process in a special way I think it is better to keep this field for grep. The patch bloats the kernel by 104 bytes and it also adds the new pointer, ->it_signal, to k_itimer. It is used by lock_timer() to verify that the found timer was not created by another process. It is not clear why do we use the global database (and thus the global idr_lock) for posix timers. We still need the signal_struct->posix_timers which contains all useable timers, perhaps it is better to use some form of per-process array instead. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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@ -45,7 +45,11 @@ struct k_itimer {
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int it_requeue_pending; /* waiting to requeue this timer */
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#define REQUEUE_PENDING 1
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int it_sigev_notify; /* notify word of sigevent struct */
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struct task_struct *it_process; /* process to send signal to */
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struct signal_struct *it_signal;
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union {
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struct pid *it_pid; /* pid of process to send signal to */
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struct task_struct *it_process; /* for clock_nanosleep */
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};
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struct sigqueue *sigq; /* signal queue entry. */
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union {
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struct {
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@ -116,7 +116,7 @@ static DEFINE_SPINLOCK(idr_lock);
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* must supply functions here, even if the function just returns
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* ENOSYS. The standard POSIX timer management code assumes the
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* following: 1.) The k_itimer struct (sched.h) is used for the
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* timer. 2.) The list, it_lock, it_clock, it_id and it_process
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* timer. 2.) The list, it_lock, it_clock, it_id and it_pid
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* fields are not modified by timer code.
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*
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* At this time all functions EXCEPT clock_nanosleep can be
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@ -313,7 +313,8 @@ void do_schedule_next_timer(struct siginfo *info)
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int posix_timer_event(struct k_itimer *timr, int si_private)
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{
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int shared, ret;
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struct task_struct *task;
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int shared, ret = -1;
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/*
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* FIXME: if ->sigq is queued we can race with
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* dequeue_signal()->do_schedule_next_timer().
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@ -327,8 +328,13 @@ int posix_timer_event(struct k_itimer *timr, int si_private)
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*/
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timr->sigq->info.si_sys_private = si_private;
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shared = !(timr->it_sigev_notify & SIGEV_THREAD_ID);
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ret = send_sigqueue(timr->sigq, timr->it_process, shared);
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rcu_read_lock();
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task = pid_task(timr->it_pid, PIDTYPE_PID);
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if (task) {
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shared = !(timr->it_sigev_notify & SIGEV_THREAD_ID);
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ret = send_sigqueue(timr->sigq, task, shared);
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}
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rcu_read_unlock();
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/* If we failed to send the signal the timer stops. */
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return ret > 0;
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}
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@ -405,7 +411,7 @@ static enum hrtimer_restart posix_timer_fn(struct hrtimer *timer)
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return ret;
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}
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static struct task_struct * good_sigevent(sigevent_t * event)
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static struct pid *good_sigevent(sigevent_t * event)
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{
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struct task_struct *rtn = current->group_leader;
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@ -419,7 +425,7 @@ static struct task_struct * good_sigevent(sigevent_t * event)
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((event->sigev_signo <= 0) || (event->sigev_signo > SIGRTMAX)))
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return NULL;
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return rtn;
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return task_pid(rtn);
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}
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void register_posix_clock(const clockid_t clock_id, struct k_clock *new_clock)
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@ -471,7 +477,7 @@ sys_timer_create(const clockid_t which_clock,
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{
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struct k_itimer *new_timer;
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int error, new_timer_id;
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struct task_struct *process;
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struct pid *it_pid;
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sigevent_t event;
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int it_id_set = IT_ID_NOT_SET;
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@ -525,11 +531,9 @@ sys_timer_create(const clockid_t which_clock,
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goto out;
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}
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rcu_read_lock();
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process = good_sigevent(&event);
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if (process)
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get_task_struct(process);
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it_pid = get_pid(good_sigevent(&event));
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rcu_read_unlock();
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if (!process) {
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if (!it_pid) {
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error = -EINVAL;
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goto out;
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}
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@ -537,8 +541,7 @@ sys_timer_create(const clockid_t which_clock,
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event.sigev_notify = SIGEV_SIGNAL;
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event.sigev_signo = SIGALRM;
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event.sigev_value.sival_int = new_timer->it_id;
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process = current->group_leader;
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get_task_struct(process);
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it_pid = get_pid(task_tgid(current));
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}
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new_timer->it_sigev_notify = event.sigev_notify;
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@ -548,7 +551,8 @@ sys_timer_create(const clockid_t which_clock,
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new_timer->sigq->info.si_code = SI_TIMER;
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spin_lock_irq(¤t->sighand->siglock);
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new_timer->it_process = process;
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new_timer->it_pid = it_pid;
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new_timer->it_signal = current->signal;
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list_add(&new_timer->list, ¤t->signal->posix_timers);
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spin_unlock_irq(¤t->sighand->siglock);
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@ -583,8 +587,7 @@ static struct k_itimer *lock_timer(timer_t timer_id, unsigned long *flags)
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timr = idr_find(&posix_timers_id, (int)timer_id);
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if (timr) {
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spin_lock(&timr->it_lock);
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if (timr->it_process &&
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same_thread_group(timr->it_process, current)) {
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if (timr->it_pid && timr->it_signal == current->signal) {
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spin_unlock(&idr_lock);
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return timr;
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}
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@ -831,8 +834,8 @@ sys_timer_delete(timer_t timer_id)
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* This keeps any tasks waiting on the spin lock from thinking
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* they got something (see the lock code above).
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*/
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put_task_struct(timer->it_process);
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timer->it_process = NULL;
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put_pid(timer->it_pid);
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timer->it_pid = NULL;
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unlock_timer(timer, flags);
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release_posix_timer(timer, IT_ID_SET);
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@ -858,8 +861,8 @@ static void itimer_delete(struct k_itimer *timer)
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* This keeps any tasks waiting on the spin lock from thinking
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* they got something (see the lock code above).
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*/
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put_task_struct(timer->it_process);
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timer->it_process = NULL;
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put_pid(timer->it_pid);
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timer->it_pid = NULL;
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unlock_timer(timer, flags);
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release_posix_timer(timer, IT_ID_SET);
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