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Commit 27af4245 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Ingo Molnar
Browse files

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: default avatarOleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 6c34bc29

include/linux/posix-timers.h

+5 −1
Original line number Diff line number Diff line
@@ -45,7 +45,11 @@ struct k_itimer { 
	int it_requeue_pending;		/* waiting to requeue this timer */

#define REQUEUE_PENDING 1

	int it_sigev_notify;		/* notify word of sigevent struct */

	struct task_struct *it_process;	/* process to send signal to */

	struct signal_struct *it_signal;

	union {

		struct pid *it_pid;	/* pid of process to send signal to */

		struct task_struct *it_process;	/* for clock_nanosleep */

	};

	struct sigqueue *sigq;		/* signal queue entry. */

	union {

		struct {

kernel/posix-timers.c

+23 −20
Original line number Diff line number Diff line
@@ -116,7 +116,7 @@ static DEFINE_SPINLOCK(idr_lock); 
 *	    must supply functions here, even if the function just returns

 *	    ENOSYS.  The standard POSIX timer management code assumes the

 *	    following: 1.) The k_itimer struct (sched.h) is used for the

 *	    timer.  2.) The list, it_lock, it_clock, it_id and it_process

 *	    timer.  2.) The list, it_lock, it_clock, it_id and it_pid

 *	    fields are not modified by timer code.

 *

 *          At this time all functions EXCEPT clock_nanosleep can be
@@ -313,7 +313,8 @@ void do_schedule_next_timer(struct siginfo *info) 


int posix_timer_event(struct k_itimer *timr, int si_private)

{

	int shared, ret;

	struct task_struct *task;

	int shared, ret = -1;

	/*

	 * FIXME: if ->sigq is queued we can race with

	 * dequeue_signal()->do_schedule_next_timer().
@@ -327,8 +328,13 @@ int posix_timer_event(struct k_itimer *timr, int si_private) 
	 */

	timr->sigq->info.si_sys_private = si_private;



	rcu_read_lock();

	task = pid_task(timr->it_pid, PIDTYPE_PID);

	if (task) {

		shared = !(timr->it_sigev_notify & SIGEV_THREAD_ID);

	ret = send_sigqueue(timr->sigq, timr->it_process, shared);

		ret = send_sigqueue(timr->sigq, task, shared);

	}

	rcu_read_unlock();

	/* If we failed to send the signal the timer stops. */

	return ret > 0;

}
@@ -405,7 +411,7 @@ static enum hrtimer_restart posix_timer_fn(struct hrtimer *timer) 
	return ret;

}



static struct task_struct * good_sigevent(sigevent_t * event)

static struct pid *good_sigevent(sigevent_t * event)

{

	struct task_struct *rtn = current->group_leader;
@@ -419,7 +425,7 @@ static struct task_struct * good_sigevent(sigevent_t * event) 
	    ((event->sigev_signo <= 0) || (event->sigev_signo > SIGRTMAX)))

		return NULL;



	return rtn;

	return task_pid(rtn);

}



void register_posix_clock(const clockid_t clock_id, struct k_clock *new_clock)
@@ -471,7 +477,7 @@ sys_timer_create(const clockid_t which_clock, 
{

	struct k_itimer *new_timer;

	int error, new_timer_id;

	struct task_struct *process;

	struct pid *it_pid;

	sigevent_t event;

	int it_id_set = IT_ID_NOT_SET;
@@ -525,11 +531,9 @@ sys_timer_create(const clockid_t which_clock, 
			goto out;

		}

		rcu_read_lock();

		process = good_sigevent(&event);

		if (process)

			get_task_struct(process);

		it_pid = get_pid(good_sigevent(&event));

		rcu_read_unlock();

		if (!process) {

		if (!it_pid) {

			error = -EINVAL;

			goto out;

		}
@@ -537,8 +541,7 @@ sys_timer_create(const clockid_t which_clock, 
		event.sigev_notify = SIGEV_SIGNAL;

		event.sigev_signo = SIGALRM;

		event.sigev_value.sival_int = new_timer->it_id;

		process = current->group_leader;

		get_task_struct(process);

		it_pid = get_pid(task_tgid(current));

	}



	new_timer->it_sigev_notify     = event.sigev_notify;
@@ -548,7 +551,8 @@ sys_timer_create(const clockid_t which_clock, 
	new_timer->sigq->info.si_code  = SI_TIMER;



	spin_lock_irq(&current->sighand->siglock);

	new_timer->it_process = process;

	new_timer->it_pid = it_pid;

	new_timer->it_signal = current->signal;

	list_add(&new_timer->list, &current->signal->posix_timers);

	spin_unlock_irq(&current->sighand->siglock);
@@ -583,8 +587,7 @@ static struct k_itimer *lock_timer(timer_t timer_id, unsigned long *flags) 
	timr = idr_find(&posix_timers_id, (int)timer_id);

	if (timr) {

		spin_lock(&timr->it_lock);

		if (timr->it_process &&

		    same_thread_group(timr->it_process, current)) {

		if (timr->it_pid && timr->it_signal == current->signal) {

			spin_unlock(&idr_lock);

			return timr;

		}
@@ -831,8 +834,8 @@ sys_timer_delete(timer_t timer_id) 
	 * This keeps any tasks waiting on the spin lock from thinking

	 * they got something (see the lock code above).

	 */

	put_task_struct(timer->it_process);

	timer->it_process = NULL;

	put_pid(timer->it_pid);

	timer->it_pid = NULL;



	unlock_timer(timer, flags);

	release_posix_timer(timer, IT_ID_SET);
@@ -858,8 +861,8 @@ static void itimer_delete(struct k_itimer *timer) 
	 * This keeps any tasks waiting on the spin lock from thinking

	 * they got something (see the lock code above).

	 */

	put_task_struct(timer->it_process);

	timer->it_process = NULL;

	put_pid(timer->it_pid);

	timer->it_pid = NULL;



	unlock_timer(timer, flags);

	release_posix_timer(timer, IT_ID_SET);