Commit 0360ed14 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

signal: Refactor send_sigqueue() 



To handle posix timers which have their signal ignored via SIG_IGN properly
it is required to requeue a ignored signal for delivery when SIG_IGN is
lifted so the timer gets rearmed.

Split the required code out of send_sigqueue() so it can be reused in
context of sigaction().

While at it rename send_sigqueue() to posixtimer_send_sigqueue() so its
clear what this is about.

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/20241105064213.586453412@linutronix.de
parent ef1c5bcd

include/linux/posix-timers.h

+1 −0
Original line number Diff line number Diff line
@@ -109,6 +109,7 @@ static inline void posix_cputimers_rt_watchdog(struct posix_cputimers *pct, 


void posixtimer_rearm_itimer(struct task_struct *p);

bool posixtimer_init_sigqueue(struct sigqueue *q);

int posixtimer_send_sigqueue(struct k_itimer *tmr);

bool posixtimer_deliver_signal(struct kernel_siginfo *info);

void posixtimer_free_timer(struct k_itimer *timer);

include/linux/sched/signal.h

+0 −1
Original line number Diff line number Diff line
@@ -340,7 +340,6 @@ extern int send_sig(int, struct task_struct *, int); 
extern int zap_other_threads(struct task_struct *p);

extern struct sigqueue *sigqueue_alloc(void);

extern void sigqueue_free(struct sigqueue *);

extern int send_sigqueue(struct sigqueue *, struct pid *, enum pid_type, int si_private);

extern int do_sigaction(int, struct k_sigaction *, struct k_sigaction *);



static inline void clear_notify_signal(void)

kernel/signal.c

+45 −37
Original line number Diff line number Diff line
@@ -1947,21 +1947,17 @@ void sigqueue_free(struct sigqueue *q) 
		__sigqueue_free(q);

}



int send_sigqueue(struct sigqueue *q, struct pid *pid, enum pid_type type, int si_private)

static void posixtimer_queue_sigqueue(struct sigqueue *q, struct task_struct *t, enum pid_type type)

{

	int sig = q->info.si_signo;

	struct sigpending *pending;

	struct task_struct *t;

	unsigned long flags;

	int ret, result;



	if (WARN_ON_ONCE(!(q->flags & SIGQUEUE_PREALLOC)))

		return 0;

	if (WARN_ON_ONCE(q->info.si_code != SI_TIMER))

		return 0;

	int sig = q->info.si_signo;



	ret = -1;

	rcu_read_lock();

	signalfd_notify(t, sig);

	pending = (type != PIDTYPE_PID) ? &t->signal->shared_pending : &t->pending;

	list_add_tail(&q->list, &pending->list);

	sigaddset(&pending->signal, sig);

	complete_signal(sig, t, type);

}



/*

 * This function is used by POSIX timers to deliver a timer signal.
@@ -1974,13 +1970,31 @@ int send_sigqueue(struct sigqueue *q, struct pid *pid, enum pid_type type, int s 
 * the same thread group as the target process, which avoids

 * unnecessarily waking up a potentially idle task.

 */

	t = pid_task(pid, type);

	if (!t)

		goto ret;

	if (type != PIDTYPE_PID && same_thread_group(t, current))

static inline struct task_struct *posixtimer_get_target(struct k_itimer *tmr)

{

	struct task_struct *t = pid_task(tmr->it_pid, tmr->it_pid_type);



	if (t && tmr->it_pid_type != PIDTYPE_PID && same_thread_group(t, current))

		t = current;

	return t;

}



int posixtimer_send_sigqueue(struct k_itimer *tmr)

{

	struct sigqueue *q = tmr->sigq;

	int sig = q->info.si_signo;

	struct task_struct *t;

	unsigned long flags;

	int ret, result;



	guard(rcu)();



	t = posixtimer_get_target(tmr);

	if (!t)

		return -1;



	if (!likely(lock_task_sighand(t, &flags)))

		goto ret;

		return -1;



	/*

	 * Update @q::info::si_sys_private for posix timer signals with
@@ -1988,30 +2002,24 @@ int send_sigqueue(struct sigqueue *q, struct pid *pid, enum pid_type type, int s 
	 * decides based on si_sys_private whether to invoke

	 * posixtimer_rearm() or not.

	 */

	q->info.si_sys_private = si_private;

	q->info.si_sys_private = tmr->it_signal_seq;



	ret = 1; /* the signal is ignored */

	if (!prepare_signal(sig, t, false)) {

		result = TRACE_SIGNAL_IGNORED;

	if (!prepare_signal(sig, t, false))

		goto out;

	}



	ret = 0;

	if (unlikely(!list_empty(&q->list))) {

		result = TRACE_SIGNAL_ALREADY_PENDING;

		goto out;

	}



	signalfd_notify(t, sig);

	pending = (type != PIDTYPE_PID) ? &t->signal->shared_pending : &t->pending;

	list_add_tail(&q->list, &pending->list);

	sigaddset(&pending->signal, sig);

	complete_signal(sig, t, type);

	posixtimer_queue_sigqueue(q, t, tmr->it_pid_type);

	result = TRACE_SIGNAL_DELIVERED;

out:

	trace_signal_generate(sig, &q->info, t, type != PIDTYPE_PID, result);

	trace_signal_generate(sig, &q->info, t, tmr->it_pid_type != PIDTYPE_PID, result);

	unlock_task_sighand(t, &flags);

ret:

	rcu_read_unlock();

	return ret;

}

#endif /* CONFIG_POSIX_TIMERS */

kernel/time/posix-timers.c

+1 −1
Original line number Diff line number Diff line
@@ -307,7 +307,7 @@ int posix_timer_queue_signal(struct k_itimer *timr) 


	timr->it_status = state;



	ret = send_sigqueue(timr->sigq, timr->it_pid, timr->it_pid_type, timr->it_signal_seq);

	ret = posixtimer_send_sigqueue(timr);

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

	return ret > 0;

}