2024-06-10 17:34:14

by Thomas Gleixner

Subject: [patch V3 46/51] 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: Thomas Gleixner <[email protected]>
---
include/linux/posix-timers.h | 4 +++-
kernel/time/posix-timers.c | 20 ++++++++++++++++++++
2 files changed, 23 insertions(+), 1 deletion(-)

--- a/include/linux/posix-timers.h
+++ b/include/linux/posix-timers.h
@@ -151,7 +151,8 @@ static inline void posix_cputimers_init_

/**
* 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
@@ -174,6 +175,7 @@ static inline void posix_cputimers_init_
*/
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;
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -1036,6 +1036,18 @@ int common_timer_del(struct k_itimer *ti
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;
@@ -1068,6 +1080,7 @@ SYSCALL_DEFINE1(timer_delete, timer_t, t

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
@@ -1119,6 +1132,8 @@ static void itimer_delete(struct k_itime
}
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
@@ -1151,6 +1166,11 @@ void exit_itimers(struct task_struct *ts
/* The timers are not longer accessible via tsk::signal */
while (!hlist_empty(&timers))
itimer_delete(hlist_entry(timers.first, struct k_itimer, list));
+
+ /* Mop up timers which are on the ignored list */
+ hlist_move_list(&tsk->signal->ignored_posix_timers, &timers);
+ while (!hlist_empty(&timers))
+ posix_timer_cleanup_ignored(hlist_entry(timers.first, struct k_itimer, list));
}

SYSCALL_DEFINE2(clock_settime, const clockid_t, which_clock,