Commit 0e20cd33 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

posix-timers: Handle ignored list on delete and exit 



To handle posix timer signals on sigaction(SIG_IGN) properly, the timers
will be queued on a separate ignored list.

Add the necessary cleanup code for timer_delete() and exit_itimers().

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241105064213.987530588@linutronix.de
parent 69f032c9

include/linux/posix-timers.h

+3 −1
Original line number Diff line number Diff line
@@ -152,7 +152,8 @@ static inline void posix_cputimers_init_work(void) { } 


/**

 * struct k_itimer - POSIX.1b interval timer structure.

 * @list:		List head for binding the timer to signals->posix_timers

 * @list:		List node for binding the timer to tsk::signal::posix_timers

 * @ignored_list:	List node for tracking ignored timers in tsk::signal::ignored_posix_timers

 * @t_hash:		Entry in the posix timer hash table

 * @it_lock:		Lock protecting the timer

 * @kclock:		Pointer to the k_clock struct handling this timer
@@ -176,6 +177,7 @@ static inline void posix_cputimers_init_work(void) { } 
 */

struct k_itimer {

	struct hlist_node	list;

	struct hlist_node	ignored_list;

	struct hlist_node	t_hash;

	spinlock_t		it_lock;

	const struct k_clock	*kclock;

kernel/time/posix-timers.c

+28 −0
Original line number Diff line number Diff line
@@ -1027,6 +1027,18 @@ int common_timer_del(struct k_itimer *timer) 
	return 0;

}



/*

 * If the deleted timer is on the ignored list, remove it and

 * drop the associated reference.

 */

static inline void posix_timer_cleanup_ignored(struct k_itimer *tmr)

{

	if (!hlist_unhashed(&tmr->ignored_list)) {

		hlist_del_init(&tmr->ignored_list);

		posixtimer_putref(tmr);

	}

}



static inline int timer_delete_hook(struct k_itimer *timer)

{

	const struct k_clock *kc = timer->kclock;
@@ -1059,6 +1071,7 @@ SYSCALL_DEFINE1(timer_delete, timer_t, timer_id) 


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

	hlist_del(&timer->list);

	posix_timer_cleanup_ignored(timer);

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

	/*

	 * A concurrent lookup could check timer::it_signal lockless. It
@@ -1110,6 +1123,8 @@ static void itimer_delete(struct k_itimer *timer) 
	}

	hlist_del(&timer->list);



	posix_timer_cleanup_ignored(timer);



	/*

	 * Setting timer::it_signal to NULL is technically not required

	 * here as nothing can access the timer anymore legitimately via
@@ -1142,6 +1157,19 @@ void exit_itimers(struct task_struct *tsk) 
	/* The timers are not longer accessible via tsk::signal */

	while (!hlist_empty(&timers))

		itimer_delete(hlist_entry(timers.first, struct k_itimer, list));



	/*

	 * There should be no timers on the ignored list. itimer_delete() has

	 * mopped them up.

	 */

	if (!WARN_ON_ONCE(!hlist_empty(&tsk->signal->ignored_posix_timers)))

		return;



	hlist_move_list(&tsk->signal->ignored_posix_timers, &timers);

	while (!hlist_empty(&timers)) {

		posix_timer_cleanup_ignored(hlist_entry(timers.first, struct k_itimer,

							ignored_list));

	}

}



SYSCALL_DEFINE2(clock_settime, const clockid_t, which_clock,