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Message-ID: <20240410165553.452316924@linutronix.de>
Date: Thu, 11 Apr 2024 00:47:22 +0200 (CEST)
From: Thomas Gleixner <tglx@...utronix.de>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Anna-Maria Behnsen <anna-maria@...utronix.de>,
Frederic Weisbecker <frederic@...nel.org>,
John Stultz <jstultz@...gle.com>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...nel.org>,
Stephen Boyd <sboyd@...nel.org>,
Eric Biederman <ebiederm@...ssion.com>,
Oleg Nesterov <oleg@...hat.com>
Subject: [patch V2 40/50] signal: Refactor send_sigqueue()
To handle posix timers which have their signal ignored via SIG_IGN properly
its 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@...utronix.de>
---
include/linux/posix-timers.h | 1
include/linux/sched/signal.h | 1
kernel/signal.c | 73 ++++++++++++++++++++++++-------------------
kernel/time/posix-timers.c | 2 -
4 files changed, 44 insertions(+), 33 deletions(-)
--- a/include/linux/posix-timers.h
+++ b/include/linux/posix-timers.h
@@ -109,6 +109,7 @@ static inline void posix_cputimers_rt_wa
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);
--- a/include/linux/sched/signal.h
+++ b/include/linux/sched/signal.h
@@ -339,7 +339,6 @@ extern int send_sig(int, struct task_str
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)
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1951,38 +1951,53 @@ 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;
-
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;
+
if (!likely(lock_task_sighand(t, &flags)))
goto ret;
@@ -1992,7 +2007,7 @@ int send_sigqueue(struct sigqueue *q, st
* 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;
/*
* Set the overrun count to zero unconditionally. The posix timer
@@ -2023,24 +2038,20 @@ int send_sigqueue(struct sigqueue *q, st
q->info.si_overrun = 0;
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();
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -308,7 +308,7 @@ int posix_timer_queue_signal(struct k_it
}
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;
}
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