diff options
Diffstat (limited to '')
| -rw-r--r-- | debian/patches-rt/0099-hrtimers-Prepare-full-preemption.patch | 290 |
1 files changed, 290 insertions, 0 deletions
diff --git a/debian/patches-rt/0099-hrtimers-Prepare-full-preemption.patch b/debian/patches-rt/0099-hrtimers-Prepare-full-preemption.patch new file mode 100644 index 000000000..897f91d52 --- /dev/null +++ b/debian/patches-rt/0099-hrtimers-Prepare-full-preemption.patch @@ -0,0 +1,290 @@ +From a5aed5c2dd54bdd010ed396577c328505028990d Mon Sep 17 00:00:00 2001 +From: Ingo Molnar <mingo@elte.hu> +Date: Fri, 3 Jul 2009 08:29:34 -0500 +Subject: [PATCH 099/347] hrtimers: Prepare full preemption +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.246-rt110.tar.xz + +Make cancellation of a running callback in softirq context safe +against preemption. + +Signed-off-by: Ingo Molnar <mingo@elte.hu> +Signed-off-by: Thomas Gleixner <tglx@linutronix.de> +--- + fs/timerfd.c | 5 ++++- + include/linux/hrtimer.h | 13 +++++++++++- + include/linux/posix-timers.h | 2 +- + kernel/time/alarmtimer.c | 2 +- + kernel/time/hrtimer.c | 33 +++++++++++++++++++++++++++++- + kernel/time/itimer.c | 1 + + kernel/time/posix-timers.c | 39 ++++++++++++++++++++++++++++++++++-- + 7 files changed, 88 insertions(+), 7 deletions(-) + +diff --git a/fs/timerfd.c b/fs/timerfd.c +index d69ad801eb80..82d0f52414a6 100644 +--- a/fs/timerfd.c ++++ b/fs/timerfd.c +@@ -471,7 +471,10 @@ static int do_timerfd_settime(int ufd, int flags, + break; + } + spin_unlock_irq(&ctx->wqh.lock); +- cpu_relax(); ++ if (isalarm(ctx)) ++ hrtimer_wait_for_timer(&ctx->t.alarm.timer); ++ else ++ hrtimer_wait_for_timer(&ctx->t.tmr); + } + + /* +diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h +index cbd041b22088..8714f1a37d84 100644 +--- a/include/linux/hrtimer.h ++++ b/include/linux/hrtimer.h +@@ -22,6 +22,7 @@ + #include <linux/percpu.h> + #include <linux/timer.h> + #include <linux/timerqueue.h> ++#include <linux/wait.h> + + struct hrtimer_clock_base; + struct hrtimer_cpu_base; +@@ -216,6 +217,9 @@ struct hrtimer_cpu_base { + ktime_t expires_next; + struct hrtimer *next_timer; + ktime_t softirq_expires_next; ++#ifdef CONFIG_PREEMPT_RT_BASE ++ wait_queue_head_t wait; ++#endif + struct hrtimer *softirq_next_timer; + struct hrtimer_clock_base clock_base[HRTIMER_MAX_CLOCK_BASES]; + } ____cacheline_aligned; +@@ -433,6 +437,13 @@ static inline void hrtimer_restart(struct hrtimer *timer) + hrtimer_start_expires(timer, HRTIMER_MODE_ABS); + } + ++/* Softirq preemption could deadlock timer removal */ ++#ifdef CONFIG_PREEMPT_RT_BASE ++ extern void hrtimer_wait_for_timer(const struct hrtimer *timer); ++#else ++# define hrtimer_wait_for_timer(timer) do { cpu_relax(); } while (0) ++#endif ++ + /* Query timers: */ + extern ktime_t __hrtimer_get_remaining(const struct hrtimer *timer, bool adjust); + +@@ -464,7 +475,7 @@ static inline bool hrtimer_is_queued(struct hrtimer *timer) + * Helper function to check, whether the timer is running the callback + * function + */ +-static inline int hrtimer_callback_running(struct hrtimer *timer) ++static inline int hrtimer_callback_running(const struct hrtimer *timer) + { + return timer->base->running == timer; + } +diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h +index ee7e987ea1b4..0571b498db73 100644 +--- a/include/linux/posix-timers.h ++++ b/include/linux/posix-timers.h +@@ -114,8 +114,8 @@ struct k_itimer { + struct { + struct alarm alarmtimer; + } alarm; +- struct rcu_head rcu; + } it; ++ struct rcu_head rcu; + }; + + void run_posix_cpu_timers(struct task_struct *task); +diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c +index 6a2ba39889bd..f4c8cfde00b0 100644 +--- a/kernel/time/alarmtimer.c ++++ b/kernel/time/alarmtimer.c +@@ -438,7 +438,7 @@ int alarm_cancel(struct alarm *alarm) + int ret = alarm_try_to_cancel(alarm); + if (ret >= 0) + return ret; +- cpu_relax(); ++ hrtimer_wait_for_timer(&alarm->timer); + } + } + EXPORT_SYMBOL_GPL(alarm_cancel); +diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c +index 1e03d7fab81c..8bbde17325c7 100644 +--- a/kernel/time/hrtimer.c ++++ b/kernel/time/hrtimer.c +@@ -957,6 +957,33 @@ u64 hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval) + } + EXPORT_SYMBOL_GPL(hrtimer_forward); + ++#ifdef CONFIG_PREEMPT_RT_BASE ++# define wake_up_timer_waiters(b) wake_up(&(b)->wait) ++ ++/** ++ * hrtimer_wait_for_timer - Wait for a running timer ++ * ++ * @timer: timer to wait for ++ * ++ * The function waits in case the timers callback function is ++ * currently executed on the waitqueue of the timer base. The ++ * waitqueue is woken up after the timer callback function has ++ * finished execution. ++ */ ++void hrtimer_wait_for_timer(const struct hrtimer *timer) ++{ ++ struct hrtimer_clock_base *base = timer->base; ++ ++ if (base && base->cpu_base && ++ base->index >= HRTIMER_BASE_MONOTONIC_SOFT) ++ wait_event(base->cpu_base->wait, ++ !(hrtimer_callback_running(timer))); ++} ++ ++#else ++# define wake_up_timer_waiters(b) do { } while (0) ++#endif ++ + /* + * enqueue_hrtimer - internal function to (re)start a timer + * +@@ -1238,7 +1265,7 @@ int hrtimer_cancel(struct hrtimer *timer) + + if (ret >= 0) + return ret; +- cpu_relax(); ++ hrtimer_wait_for_timer(timer); + } + } + EXPORT_SYMBOL_GPL(hrtimer_cancel); +@@ -1544,6 +1571,7 @@ static __latent_entropy void hrtimer_run_softirq(struct softirq_action *h) + hrtimer_update_softirq_timer(cpu_base, true); + + raw_spin_unlock_irqrestore(&cpu_base->lock, flags); ++ wake_up_timer_waiters(cpu_base); + } + + #ifdef CONFIG_HIGH_RES_TIMERS +@@ -1913,6 +1941,9 @@ int hrtimers_prepare_cpu(unsigned int cpu) + cpu_base->softirq_next_timer = NULL; + cpu_base->expires_next = KTIME_MAX; + cpu_base->softirq_expires_next = KTIME_MAX; ++#ifdef CONFIG_PREEMPT_RT_BASE ++ init_waitqueue_head(&cpu_base->wait); ++#endif + return 0; + } + +diff --git a/kernel/time/itimer.c b/kernel/time/itimer.c +index 2e2b335ef101..7650ee736964 100644 +--- a/kernel/time/itimer.c ++++ b/kernel/time/itimer.c +@@ -211,6 +211,7 @@ int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue) + /* We are sharing ->siglock with it_real_fn() */ + if (hrtimer_try_to_cancel(timer) < 0) { + spin_unlock_irq(&tsk->sighand->siglock); ++ hrtimer_wait_for_timer(&tsk->signal->real_timer); + goto again; + } + expires = timeval_to_ktime(value->it_value); +diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c +index 48758108e055..2cf5aa704106 100644 +--- a/kernel/time/posix-timers.c ++++ b/kernel/time/posix-timers.c +@@ -463,7 +463,7 @@ static struct k_itimer * alloc_posix_timer(void) + + static void k_itimer_rcu_free(struct rcu_head *head) + { +- struct k_itimer *tmr = container_of(head, struct k_itimer, it.rcu); ++ struct k_itimer *tmr = container_of(head, struct k_itimer, rcu); + + kmem_cache_free(posix_timers_cache, tmr); + } +@@ -480,7 +480,7 @@ static void release_posix_timer(struct k_itimer *tmr, int it_id_set) + } + put_pid(tmr->it_pid); + sigqueue_free(tmr->sigq); +- call_rcu(&tmr->it.rcu, k_itimer_rcu_free); ++ call_rcu(&tmr->rcu, k_itimer_rcu_free); + } + + static int common_timer_create(struct k_itimer *new_timer) +@@ -821,6 +821,22 @@ static void common_hrtimer_arm(struct k_itimer *timr, ktime_t expires, + hrtimer_start_expires(timer, HRTIMER_MODE_ABS); + } + ++/* ++ * Protected by RCU! ++ */ ++static void timer_wait_for_callback(const struct k_clock *kc, struct k_itimer *timr) ++{ ++#ifdef CONFIG_PREEMPT_RT_FULL ++ if (kc->timer_arm == common_hrtimer_arm) ++ hrtimer_wait_for_timer(&timr->it.real.timer); ++ else if (kc == &alarm_clock) ++ hrtimer_wait_for_timer(&timr->it.alarm.alarmtimer.timer); ++ else ++ /* FIXME: Whacky hack for posix-cpu-timers */ ++ schedule_timeout(1); ++#endif ++} ++ + static int common_hrtimer_try_to_cancel(struct k_itimer *timr) + { + return hrtimer_try_to_cancel(&timr->it.real.timer); +@@ -885,6 +901,7 @@ static int do_timer_settime(timer_t timer_id, int flags, + if (!timr) + return -EINVAL; + ++ rcu_read_lock(); + kc = timr->kclock; + if (WARN_ON_ONCE(!kc || !kc->timer_set)) + error = -EINVAL; +@@ -893,9 +910,12 @@ static int do_timer_settime(timer_t timer_id, int flags, + + unlock_timer(timr, flag); + if (error == TIMER_RETRY) { ++ timer_wait_for_callback(kc, timr); + old_spec64 = NULL; // We already got the old time... ++ rcu_read_unlock(); + goto retry; + } ++ rcu_read_unlock(); + + return error; + } +@@ -977,10 +997,15 @@ SYSCALL_DEFINE1(timer_delete, timer_t, timer_id) + if (!timer) + return -EINVAL; + ++ rcu_read_lock(); + if (timer_delete_hook(timer) == TIMER_RETRY) { + unlock_timer(timer, flags); ++ timer_wait_for_callback(clockid_to_kclock(timer->it_clock), ++ timer); ++ rcu_read_unlock(); + goto retry_delete; + } ++ rcu_read_unlock(); + + spin_lock(¤t->sighand->siglock); + list_del(&timer->list); +@@ -1006,8 +1031,18 @@ static void itimer_delete(struct k_itimer *timer) + retry_delete: + spin_lock_irqsave(&timer->it_lock, flags); + ++ /* On RT we can race with a deletion */ ++ if (!timer->it_signal) { ++ unlock_timer(timer, flags); ++ return; ++ } ++ + if (timer_delete_hook(timer) == TIMER_RETRY) { ++ rcu_read_lock(); + unlock_timer(timer, flags); ++ timer_wait_for_callback(clockid_to_kclock(timer->it_clock), ++ timer); ++ rcu_read_unlock(); + goto retry_delete; + } + list_del(&timer->list); +-- +2.36.1 + |