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Message-ID: <ZyTb-oMrREz006d5@localhost.localdomain>
Date: Fri, 1 Nov 2024 14:47:38 +0100
From: Frederic Weisbecker <frederic@...nel.org>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: LKML <linux-kernel@...r.kernel.org>,
Anna-Maria Behnsen <anna-maria@...utronix.de>,
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: Re: [patch v6 15/20] posix-timers: Handle ignored list on delete and
exit
Le Thu, Oct 31, 2024 at 04:46:41PM +0100, Thomas Gleixner a écrit :
> From: Thomas Gleixner <tglx@...utronix.de>
>
> 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 <tglx@...utronix.de>
> Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
> V6: Warn when the ignored list is not empty after deleting all timers in
> exit_itimers()
> ---
> include/linux/posix-timers.h | 4 +++-
> kernel/time/posix-timers.c | 26 ++++++++++++++++++++++++++
> 2 files changed, 29 insertions(+), 1 deletion(-)
> ---
>
> --- a/include/linux/posix-timers.h
> +++ b/include/linux/posix-timers.h
> @@ -152,7 +152,8 @@ 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
> @@ -176,6 +177,7 @@ 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
> @@ -1027,6 +1027,18 @@ 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;
> @@ -1059,6 +1071,7 @@ SYSCALL_DEFINE1(timer_delete, timer_t, t
>
> spin_lock(¤t->sighand->siglock);
> hlist_del(&timer->list);
> + posix_timer_cleanup_ignored(timer);
> spin_unlock(¤t->sighand->siglock);
> /*
> * A concurrent lookup could check timer::it_signal lockless. It
> @@ -1110,6 +1123,8 @@ 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
> @@ -1142,6 +1157,17 @@ 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));
> +
> + /*
> + * 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, list));
s/list/ignored_list ?
Other than that:
Reviewed-by: Frederic Weisbecker <frederic@...nel.org>
> }
>
> SYSCALL_DEFINE2(clock_settime, const clockid_t, which_clock,
>
>
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