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signal: Refactor send_sigqueue()

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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: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241105064213.586453412@linutronix.de
This commit is contained in:
Thomas Gleixner 2024-11-05 09:14:42 +01:00
parent ef1c5bcd6d
commit 0360ed14d9
4 changed files with 47 additions and 39 deletions
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1
include/linux/posix-timers.h
View File

@ -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);

1
include/linux/sched/signal.h
View File

@ -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)

82
kernel/signal.c
View File

@ -1947,40 +1947,54 @@ 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;
int sig = q->info.si_signo;
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.
* Where type is PIDTYPE_PID (such as for timers with SIGEV_THREAD_ID
* set), the signal must be delivered to the specific thread (queues
* into t->pending).
*
* Where type is not PIDTYPE_PID, signals must be delivered to the
* process. In this case, prefer to deliver to current if it is in
* the same thread group as the target process, which avoids
* unnecessarily waking up a potentially idle task.
*/
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;
if (WARN_ON_ONCE(!(q->flags & SIGQUEUE_PREALLOC)))
return 0;
if (WARN_ON_ONCE(q->info.si_code != SI_TIMER))
return 0;
guard(rcu)();
ret = -1;
rcu_read_lock();
/*
* This function is used by POSIX timers to deliver a timer signal.
* Where type is PIDTYPE_PID (such as for timers with SIGEV_THREAD_ID
* set), the signal must be delivered to the specific thread (queues
* into t->pending).
*
* Where type is not PIDTYPE_PID, signals must be delivered to the
* process. In this case, prefer to deliver to current if it is in
* the same thread group as the target process, which avoids
* unnecessarily waking up a potentially idle task.
*/
t = pid_task(pid, type);
t = posixtimer_get_target(tmr);
if (!t)
goto ret;
if (type != PIDTYPE_PID && same_thread_group(t, current))
t = current;
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 */
result = TRACE_SIGNAL_IGNORED;
if (!prepare_signal(sig, t, false))
if (!prepare_signal(sig, t, false)) {
result = TRACE_SIGNAL_IGNORED;
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 */

2
kernel/time/posix-timers.c
View File

@ -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;
}