Update Linux to v5.4.2
Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index e1a549c..6560553 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1,34 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0
/*
- * linux/kernel/hrtimer.c
- *
* Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
* Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
* Copyright(C) 2006-2007 Timesys Corp., Thomas Gleixner
*
* High-resolution kernel timers
*
- * In contrast to the low-resolution timeout API implemented in
- * kernel/timer.c, hrtimers provide finer resolution and accuracy
- * depending on system configuration and capabilities.
- *
- * These timers are currently used for:
- * - itimers
- * - POSIX timers
- * - nanosleep
- * - precise in-kernel timing
+ * In contrast to the low-resolution timeout API, aka timer wheel,
+ * hrtimers provide finer resolution and accuracy depending on system
+ * configuration and capabilities.
*
* Started by: Thomas Gleixner and Ingo Molnar
*
* Credits:
- * based on kernel/timer.c
+ * Based on the original timer wheel code
*
* Help, testing, suggestions, bugfixes, improvements were
* provided by:
*
* George Anzinger, Andrew Morton, Steven Rostedt, Roman Zippel
* et. al.
- *
- * For licencing details see kernel-base/COPYING
*/
#include <linux/cpu.h>
@@ -39,7 +30,6 @@
#include <linux/syscalls.h>
#include <linux/interrupt.h>
#include <linux/tick.h>
-#include <linux/seq_file.h>
#include <linux/err.h>
#include <linux/debugobjects.h>
#include <linux/sched/signal.h>
@@ -150,6 +140,11 @@
#define migration_base migration_cpu_base.clock_base[0]
+static inline bool is_migration_base(struct hrtimer_clock_base *base)
+{
+ return base == &migration_base;
+}
+
/*
* We are using hashed locking: holding per_cpu(hrtimer_bases)[n].lock
* means that all timers which are tied to this base via timer->base are
@@ -169,7 +164,7 @@
struct hrtimer_clock_base *base;
for (;;) {
- base = timer->base;
+ base = READ_ONCE(timer->base);
if (likely(base != &migration_base)) {
raw_spin_lock_irqsave(&base->cpu_base->lock, *flags);
if (likely(base == timer->base))
@@ -249,7 +244,7 @@
return base;
/* See the comment in lock_hrtimer_base() */
- timer->base = &migration_base;
+ WRITE_ONCE(timer->base, &migration_base);
raw_spin_unlock(&base->cpu_base->lock);
raw_spin_lock(&new_base->cpu_base->lock);
@@ -258,10 +253,10 @@
raw_spin_unlock(&new_base->cpu_base->lock);
raw_spin_lock(&base->cpu_base->lock);
new_cpu_base = this_cpu_base;
- timer->base = base;
+ WRITE_ONCE(timer->base, base);
goto again;
}
- timer->base = new_base;
+ WRITE_ONCE(timer->base, new_base);
} else {
if (new_cpu_base != this_cpu_base &&
hrtimer_check_target(timer, new_base)) {
@@ -274,6 +269,11 @@
#else /* CONFIG_SMP */
+static inline bool is_migration_base(struct hrtimer_clock_base *base)
+{
+ return false;
+}
+
static inline struct hrtimer_clock_base *
lock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
{
@@ -373,7 +373,7 @@
switch (state) {
case ODEBUG_STATE_ACTIVE:
WARN_ON(1);
-
+ /* fall through */
default:
return false;
}
@@ -437,6 +437,17 @@
}
EXPORT_SYMBOL_GPL(hrtimer_init_on_stack);
+static void __hrtimer_init_sleeper(struct hrtimer_sleeper *sl,
+ clockid_t clock_id, enum hrtimer_mode mode);
+
+void hrtimer_init_sleeper_on_stack(struct hrtimer_sleeper *sl,
+ clockid_t clock_id, enum hrtimer_mode mode)
+{
+ debug_object_init_on_stack(&sl->timer, &hrtimer_debug_descr);
+ __hrtimer_init_sleeper(sl, clock_id, mode);
+}
+EXPORT_SYMBOL_GPL(hrtimer_init_sleeper_on_stack);
+
void destroy_hrtimer_on_stack(struct hrtimer *timer)
{
debug_object_free(timer, &hrtimer_debug_descr);
@@ -1106,9 +1117,13 @@
/*
* Check whether the HRTIMER_MODE_SOFT bit and hrtimer.is_soft
- * match.
+ * match on CONFIG_PREEMPT_RT = n. With PREEMPT_RT check the hard
+ * expiry mode because unmarked timers are moved to softirq expiry.
*/
- WARN_ON_ONCE(!(mode & HRTIMER_MODE_SOFT) ^ !timer->is_soft);
+ if (!IS_ENABLED(CONFIG_PREEMPT_RT))
+ WARN_ON_ONCE(!(mode & HRTIMER_MODE_SOFT) ^ !timer->is_soft);
+ else
+ WARN_ON_ONCE(!(mode & HRTIMER_MODE_HARD) ^ !timer->is_hard);
base = lock_hrtimer_base(timer, &flags);
@@ -1124,9 +1139,10 @@
* @timer: hrtimer to stop
*
* Returns:
- * 0 when the timer was not active
- * 1 when the timer was active
- * -1 when the timer is currently executing the callback function and
+ *
+ * * 0 when the timer was not active
+ * * 1 when the timer was active
+ * * -1 when the timer is currently executing the callback function and
* cannot be stopped
*/
int hrtimer_try_to_cancel(struct hrtimer *timer)
@@ -1156,6 +1172,93 @@
}
EXPORT_SYMBOL_GPL(hrtimer_try_to_cancel);
+#ifdef CONFIG_PREEMPT_RT
+static void hrtimer_cpu_base_init_expiry_lock(struct hrtimer_cpu_base *base)
+{
+ spin_lock_init(&base->softirq_expiry_lock);
+}
+
+static void hrtimer_cpu_base_lock_expiry(struct hrtimer_cpu_base *base)
+{
+ spin_lock(&base->softirq_expiry_lock);
+}
+
+static void hrtimer_cpu_base_unlock_expiry(struct hrtimer_cpu_base *base)
+{
+ spin_unlock(&base->softirq_expiry_lock);
+}
+
+/*
+ * The counterpart to hrtimer_cancel_wait_running().
+ *
+ * If there is a waiter for cpu_base->expiry_lock, then it was waiting for
+ * the timer callback to finish. Drop expiry_lock and reaquire it. That
+ * allows the waiter to acquire the lock and make progress.
+ */
+static void hrtimer_sync_wait_running(struct hrtimer_cpu_base *cpu_base,
+ unsigned long flags)
+{
+ if (atomic_read(&cpu_base->timer_waiters)) {
+ raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
+ spin_unlock(&cpu_base->softirq_expiry_lock);
+ spin_lock(&cpu_base->softirq_expiry_lock);
+ raw_spin_lock_irq(&cpu_base->lock);
+ }
+}
+
+/*
+ * This function is called on PREEMPT_RT kernels when the fast path
+ * deletion of a timer failed because the timer callback function was
+ * running.
+ *
+ * This prevents priority inversion: if the soft irq thread is preempted
+ * in the middle of a timer callback, then calling del_timer_sync() can
+ * lead to two issues:
+ *
+ * - If the caller is on a remote CPU then it has to spin wait for the timer
+ * handler to complete. This can result in unbound priority inversion.
+ *
+ * - If the caller originates from the task which preempted the timer
+ * handler on the same CPU, then spin waiting for the timer handler to
+ * complete is never going to end.
+ */
+void hrtimer_cancel_wait_running(const struct hrtimer *timer)
+{
+ /* Lockless read. Prevent the compiler from reloading it below */
+ struct hrtimer_clock_base *base = READ_ONCE(timer->base);
+
+ /*
+ * Just relax if the timer expires in hard interrupt context or if
+ * it is currently on the migration base.
+ */
+ if (!timer->is_soft || is_migration_base(base)) {
+ cpu_relax();
+ return;
+ }
+
+ /*
+ * Mark the base as contended and grab the expiry lock, which is
+ * held by the softirq across the timer callback. Drop the lock
+ * immediately so the softirq can expire the next timer. In theory
+ * the timer could already be running again, but that's more than
+ * unlikely and just causes another wait loop.
+ */
+ atomic_inc(&base->cpu_base->timer_waiters);
+ spin_lock_bh(&base->cpu_base->softirq_expiry_lock);
+ atomic_dec(&base->cpu_base->timer_waiters);
+ spin_unlock_bh(&base->cpu_base->softirq_expiry_lock);
+}
+#else
+static inline void
+hrtimer_cpu_base_init_expiry_lock(struct hrtimer_cpu_base *base) { }
+static inline void
+hrtimer_cpu_base_lock_expiry(struct hrtimer_cpu_base *base) { }
+static inline void
+hrtimer_cpu_base_unlock_expiry(struct hrtimer_cpu_base *base) { }
+static inline void hrtimer_sync_wait_running(struct hrtimer_cpu_base *base,
+ unsigned long flags) { }
+#endif
+
/**
* hrtimer_cancel - cancel a timer and wait for the handler to finish.
* @timer: the timer to be cancelled
@@ -1166,13 +1269,15 @@
*/
int hrtimer_cancel(struct hrtimer *timer)
{
- for (;;) {
- int ret = hrtimer_try_to_cancel(timer);
+ int ret;
- if (ret >= 0)
- return ret;
- cpu_relax();
- }
+ do {
+ ret = hrtimer_try_to_cancel(timer);
+
+ if (ret < 0)
+ hrtimer_cancel_wait_running(timer);
+ } while (ret < 0);
+ return ret;
}
EXPORT_SYMBOL_GPL(hrtimer_cancel);
@@ -1269,8 +1374,17 @@
enum hrtimer_mode mode)
{
bool softtimer = !!(mode & HRTIMER_MODE_SOFT);
- int base = softtimer ? HRTIMER_MAX_CLOCK_BASES / 2 : 0;
struct hrtimer_cpu_base *cpu_base;
+ int base;
+
+ /*
+ * On PREEMPT_RT enabled kernels hrtimers which are not explicitely
+ * marked for hard interrupt expiry mode are moved into soft
+ * interrupt context for latency reasons and because the callbacks
+ * can invoke functions which might sleep on RT, e.g. spin_lock().
+ */
+ if (IS_ENABLED(CONFIG_PREEMPT_RT) && !(mode & HRTIMER_MODE_HARD))
+ softtimer = true;
memset(timer, 0, sizeof(struct hrtimer));
@@ -1284,8 +1398,10 @@
if (clock_id == CLOCK_REALTIME && mode & HRTIMER_MODE_REL)
clock_id = CLOCK_MONOTONIC;
+ base = softtimer ? HRTIMER_MAX_CLOCK_BASES / 2 : 0;
base += hrtimer_clockid_to_base(clock_id);
timer->is_soft = softtimer;
+ timer->is_hard = !softtimer;
timer->base = &cpu_base->clock_base[base];
timerqueue_init(&timer->node);
}
@@ -1458,6 +1574,8 @@
break;
__run_hrtimer(cpu_base, base, timer, &basenow, flags);
+ if (active_mask == HRTIMER_ACTIVE_SOFT)
+ hrtimer_sync_wait_running(cpu_base, flags);
}
}
}
@@ -1468,6 +1586,7 @@
unsigned long flags;
ktime_t now;
+ hrtimer_cpu_base_lock_expiry(cpu_base);
raw_spin_lock_irqsave(&cpu_base->lock, flags);
now = hrtimer_update_base(cpu_base);
@@ -1477,6 +1596,7 @@
hrtimer_update_softirq_timer(cpu_base, true);
raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
+ hrtimer_cpu_base_unlock_expiry(cpu_base);
}
#ifdef CONFIG_HIGH_RES_TIMERS
@@ -1648,10 +1768,75 @@
return HRTIMER_NORESTART;
}
-void hrtimer_init_sleeper(struct hrtimer_sleeper *sl, struct task_struct *task)
+/**
+ * hrtimer_sleeper_start_expires - Start a hrtimer sleeper timer
+ * @sl: sleeper to be started
+ * @mode: timer mode abs/rel
+ *
+ * Wrapper around hrtimer_start_expires() for hrtimer_sleeper based timers
+ * to allow PREEMPT_RT to tweak the delivery mode (soft/hardirq context)
+ */
+void hrtimer_sleeper_start_expires(struct hrtimer_sleeper *sl,
+ enum hrtimer_mode mode)
{
+ /*
+ * Make the enqueue delivery mode check work on RT. If the sleeper
+ * was initialized for hard interrupt delivery, force the mode bit.
+ * This is a special case for hrtimer_sleepers because
+ * hrtimer_init_sleeper() determines the delivery mode on RT so the
+ * fiddling with this decision is avoided at the call sites.
+ */
+ if (IS_ENABLED(CONFIG_PREEMPT_RT) && sl->timer.is_hard)
+ mode |= HRTIMER_MODE_HARD;
+
+ hrtimer_start_expires(&sl->timer, mode);
+}
+EXPORT_SYMBOL_GPL(hrtimer_sleeper_start_expires);
+
+static void __hrtimer_init_sleeper(struct hrtimer_sleeper *sl,
+ clockid_t clock_id, enum hrtimer_mode mode)
+{
+ /*
+ * On PREEMPT_RT enabled kernels hrtimers which are not explicitely
+ * marked for hard interrupt expiry mode are moved into soft
+ * interrupt context either for latency reasons or because the
+ * hrtimer callback takes regular spinlocks or invokes other
+ * functions which are not suitable for hard interrupt context on
+ * PREEMPT_RT.
+ *
+ * The hrtimer_sleeper callback is RT compatible in hard interrupt
+ * context, but there is a latency concern: Untrusted userspace can
+ * spawn many threads which arm timers for the same expiry time on
+ * the same CPU. That causes a latency spike due to the wakeup of
+ * a gazillion threads.
+ *
+ * OTOH, priviledged real-time user space applications rely on the
+ * low latency of hard interrupt wakeups. If the current task is in
+ * a real-time scheduling class, mark the mode for hard interrupt
+ * expiry.
+ */
+ if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
+ if (task_is_realtime(current) && !(mode & HRTIMER_MODE_SOFT))
+ mode |= HRTIMER_MODE_HARD;
+ }
+
+ __hrtimer_init(&sl->timer, clock_id, mode);
sl->timer.function = hrtimer_wakeup;
- sl->task = task;
+ sl->task = current;
+}
+
+/**
+ * hrtimer_init_sleeper - initialize sleeper to the given clock
+ * @sl: sleeper to be initialized
+ * @clock_id: the clock to be used
+ * @mode: timer mode abs/rel
+ */
+void hrtimer_init_sleeper(struct hrtimer_sleeper *sl, clockid_t clock_id,
+ enum hrtimer_mode mode)
+{
+ debug_init(&sl->timer, clock_id, mode);
+ __hrtimer_init_sleeper(sl, clock_id, mode);
+
}
EXPORT_SYMBOL_GPL(hrtimer_init_sleeper);
@@ -1660,7 +1845,7 @@
switch(restart->nanosleep.type) {
#ifdef CONFIG_COMPAT_32BIT_TIME
case TT_COMPAT:
- if (compat_put_timespec64(ts, restart->nanosleep.compat_rmtp))
+ if (put_old_timespec32(ts, restart->nanosleep.compat_rmtp))
return -EFAULT;
break;
#endif
@@ -1678,11 +1863,9 @@
{
struct restart_block *restart;
- hrtimer_init_sleeper(t, current);
-
do {
set_current_state(TASK_INTERRUPTIBLE);
- hrtimer_start_expires(&t->timer, mode);
+ hrtimer_sleeper_start_expires(t, mode);
if (likely(t->task))
freezable_schedule();
@@ -1716,10 +1899,9 @@
struct hrtimer_sleeper t;
int ret;
- hrtimer_init_on_stack(&t.timer, restart->nanosleep.clockid,
- HRTIMER_MODE_ABS);
+ hrtimer_init_sleeper_on_stack(&t, restart->nanosleep.clockid,
+ HRTIMER_MODE_ABS);
hrtimer_set_expires_tv64(&t.timer, restart->nanosleep.expires);
-
ret = do_nanosleep(&t, HRTIMER_MODE_ABS);
destroy_hrtimer_on_stack(&t.timer);
return ret;
@@ -1737,7 +1919,7 @@
if (dl_task(current) || rt_task(current))
slack = 0;
- hrtimer_init_on_stack(&t.timer, clockid, mode);
+ hrtimer_init_sleeper_on_stack(&t, clockid, mode);
hrtimer_set_expires_range_ns(&t.timer, timespec64_to_ktime(*rqtp), slack);
ret = do_nanosleep(&t, mode);
if (ret != -ERESTART_RESTARTBLOCK)
@@ -1780,12 +1962,12 @@
#ifdef CONFIG_COMPAT_32BIT_TIME
-COMPAT_SYSCALL_DEFINE2(nanosleep, struct compat_timespec __user *, rqtp,
- struct compat_timespec __user *, rmtp)
+SYSCALL_DEFINE2(nanosleep_time32, struct old_timespec32 __user *, rqtp,
+ struct old_timespec32 __user *, rmtp)
{
struct timespec64 tu;
- if (compat_get_timespec64(&tu, rqtp))
+ if (get_old_timespec32(&tu, rqtp))
return -EFAULT;
if (!timespec64_valid(&tu))
@@ -1818,6 +2000,7 @@
cpu_base->softirq_next_timer = NULL;
cpu_base->expires_next = KTIME_MAX;
cpu_base->softirq_expires_next = KTIME_MAX;
+ hrtimer_cpu_base_init_expiry_lock(cpu_base);
return 0;
}
@@ -1936,12 +2119,9 @@
return -EINTR;
}
- hrtimer_init_on_stack(&t.timer, clock_id, mode);
+ hrtimer_init_sleeper_on_stack(&t, clock_id, mode);
hrtimer_set_expires_range_ns(&t.timer, *expires, delta);
-
- hrtimer_init_sleeper(&t, current);
-
- hrtimer_start_expires(&t.timer, mode);
+ hrtimer_sleeper_start_expires(&t, mode);
if (likely(t.task))
schedule();