Commit 52f090b1 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

posix-timers: Add proper comments in do_timer_create() 



The comment about timer lifetime at the end of the function is misplaced
and uncomprehensible.

Make it understandable and put it at the right place. Add a new comment
about the visibility of the new timer ID to user space.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20230425183313.619897296@linutronix.de
parent 640fe745

kernel/time/posix-timers.c

+11 −9
Original line number Diff line number Diff line
@@ -529,12 +529,17 @@ static int do_timer_create(clockid_t which_clock, struct sigevent *event, 
	new_timer->sigq->info.si_tid   = new_timer->it_id;

	new_timer->sigq->info.si_code  = SI_TIMER;



	if (copy_to_user(created_timer_id,

			 &new_timer_id, sizeof (new_timer_id))) {

	if (copy_to_user(created_timer_id, &new_timer_id, sizeof (new_timer_id))) {

		error = -EFAULT;

		goto out;

	}



	/*

	 * After succesful copy out, the timer ID is visible to user space

	 * now but not yet valid because new_timer::signal is still NULL.

	 *

	 * Complete the initialization with the clock specific create

	 * callback.

	 */

	error = kc->timer_create(new_timer);

	if (error)

		goto out;
@@ -544,14 +549,11 @@ static int do_timer_create(clockid_t which_clock, struct sigevent *event, 
	WRITE_ONCE(new_timer->it_signal, current->signal);

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

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



	return 0;

	/*

	 * In the case of the timer belonging to another task, after

	 * the task is unlocked, the timer is owned by the other task

	 * and may cease to exist at any time.  Don't use or modify

	 * new_timer after the unlock call.

	 * After unlocking sighand::siglock @new_timer is subject to

	 * concurrent removal and cannot be touched anymore

	 */

	return 0;

out:

	posix_timer_unhash_and_free(new_timer);

	return error;