1 files changed, 177 insertions, 4 deletions

diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index 5bbad147a90c..22e4e85724af 100644
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -3,8 +3,10 @@
  * Implement CPU time clocks for the POSIX clock interface.
  */
 
+#include <uapi/linux/sched/types.h>
 #include <linux/sched/signal.h>
 #include <linux/sched/cputime.h>
+#include <linux/sched/rt.h>
 #include <linux/posix-timers.h>
 #include <linux/errno.h>
 #include <linux/math64.h>
@@ -15,6 +17,7 @@
 #include <linux/workqueue.h>
 #include <linux/compat.h>
 #include <linux/sched/deadline.h>
+#include <linux/smpboot.h>
 
 #include "posix-timers.h"
 
@@ -788,6 +791,7 @@ check_timers_list(struct list_head *timers,
 			return t->expires;
 
 		t->firing = 1;
+		t->firing_cpu = smp_processor_id();
 		list_move_tail(&t->entry, firing);
 	}
 
@@ -1131,18 +1135,31 @@ static inline int fastpath_timer_check(struct task_struct *tsk)
 	return 0;
 }
 
+static DEFINE_PER_CPU(spinlock_t, cpu_timer_expiry_lock) = __SPIN_LOCK_UNLOCKED(cpu_timer_expiry_lock);
+
+void cpu_timers_grab_expiry_lock(struct k_itimer *timer)
+{
+	int cpu = timer->it.cpu.firing_cpu;
+
+	if (cpu >= 0) {
+		spinlock_t *expiry_lock = per_cpu_ptr(&cpu_timer_expiry_lock, cpu);
+
+		spin_lock_irq(expiry_lock);
+		spin_unlock_irq(expiry_lock);
+	}
+}
+
 /*
  * This is called from the timer interrupt handler.  The irq handler has
  * already updated our counts.  We need to check if any timers fire now.
  * Interrupts are disabled.
  */
-void run_posix_cpu_timers(struct task_struct *tsk)
+static void __run_posix_cpu_timers(struct task_struct *tsk)
 {
 	LIST_HEAD(firing);
 	struct k_itimer *timer, *next;
 	unsigned long flags;
-
-	lockdep_assert_irqs_disabled();
+	spinlock_t *expiry_lock;
 
 	/*
 	 * The fast path checks that there are no expired thread or thread
@@ -1151,8 +1168,13 @@ void run_posix_cpu_timers(struct task_struct *tsk)
 	if (!fastpath_timer_check(tsk))
 		return;
 
-	if (!lock_task_sighand(tsk, &flags))
+	expiry_lock = this_cpu_ptr(&cpu_timer_expiry_lock);
+	spin_lock(expiry_lock);
+
+	if (!lock_task_sighand(tsk, &flags)) {
+		spin_unlock(expiry_lock);
 		return;
+	}
 	/*
 	 * Here we take off tsk->signal->cpu_timers[N] and
 	 * tsk->cpu_timers[N] all the timers that are firing, and
@@ -1185,6 +1207,7 @@ void run_posix_cpu_timers(struct task_struct *tsk)
 		list_del_init(&timer->it.cpu.entry);
 		cpu_firing = timer->it.cpu.firing;
 		timer->it.cpu.firing = 0;
+		timer->it.cpu.firing_cpu = -1;
 		/*
 		 * The firing flag is -1 if we collided with a reset
 		 * of the timer, which already reported this
@@ -1194,8 +1217,156 @@ void run_posix_cpu_timers(struct task_struct *tsk)
 			cpu_timer_fire(timer);
 		spin_unlock(&timer->it_lock);
 	}
+	spin_unlock(expiry_lock);
+}
+
+#ifdef CONFIG_PREEMPT_RT_BASE
+#include <linux/kthread.h>
+#include <linux/cpu.h>
+DEFINE_PER_CPU(struct task_struct *, posix_timer_task);
+DEFINE_PER_CPU(struct task_struct *, posix_timer_tasklist);
+DEFINE_PER_CPU(bool, posix_timer_th_active);
+
+static void posix_cpu_kthread_fn(unsigned int cpu)
+{
+	struct task_struct *tsk = NULL;
+	struct task_struct *next = NULL;
+
+	BUG_ON(per_cpu(posix_timer_task, cpu) != current);
+
+	/* grab task list */
+	raw_local_irq_disable();
+	tsk = per_cpu(posix_timer_tasklist, cpu);
+	per_cpu(posix_timer_tasklist, cpu) = NULL;
+	raw_local_irq_enable();
+
+	/* its possible the list is empty, just return */
+	if (!tsk)
+		return;
+
+	/* Process task list */
+	while (1) {
+		/* save next */
+		next = tsk->posix_timer_list;
+
+		/* run the task timers, clear its ptr and
+		 * unreference it
+		 */
+		__run_posix_cpu_timers(tsk);
+		tsk->posix_timer_list = NULL;
+		put_task_struct(tsk);
+
+		/* check if this is the last on the list */
+		if (next == tsk)
+			break;
+		tsk = next;
+	}
+}
+
+static inline int __fastpath_timer_check(struct task_struct *tsk)
+{
+	/* tsk == current, ensure it is safe to use ->signal/sighand */
+	if (unlikely(tsk->exit_state))
+		return 0;
+
+	if (!task_cputime_zero(&tsk->cputime_expires))
+			return 1;
+
+	if (!task_cputime_zero(&tsk->signal->cputime_expires))
+			return 1;
+
+	return 0;
 }
 
+void run_posix_cpu_timers(struct task_struct *tsk)
+{
+	unsigned int cpu = smp_processor_id();
+	struct task_struct *tasklist;
+
+	BUG_ON(!irqs_disabled());
+
+	if (per_cpu(posix_timer_th_active, cpu) != true)
+		return;
+
+	/* get per-cpu references */
+	tasklist = per_cpu(posix_timer_tasklist, cpu);
+
+	/* check to see if we're already queued */
+	if (!tsk->posix_timer_list && __fastpath_timer_check(tsk)) {
+		get_task_struct(tsk);
+		if (tasklist) {
+			tsk->posix_timer_list = tasklist;
+		} else {
+			/*
+			 * The list is terminated by a self-pointing
+			 * task_struct
+			 */
+			tsk->posix_timer_list = tsk;
+		}
+		per_cpu(posix_timer_tasklist, cpu) = tsk;
+
+		wake_up_process(per_cpu(posix_timer_task, cpu));
+	}
+}
+
+static int posix_cpu_kthread_should_run(unsigned int cpu)
+{
+	return __this_cpu_read(posix_timer_tasklist) != NULL;
+}
+
+static void posix_cpu_kthread_park(unsigned int cpu)
+{
+	this_cpu_write(posix_timer_th_active, false);
+}
+
+static void posix_cpu_kthread_unpark(unsigned int cpu)
+{
+	this_cpu_write(posix_timer_th_active, true);
+}
+
+static void posix_cpu_kthread_setup(unsigned int cpu)
+{
+	struct sched_param sp;
+
+	sp.sched_priority = MAX_RT_PRIO - 1;
+	sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
+	posix_cpu_kthread_unpark(cpu);
+}
+
+static struct smp_hotplug_thread posix_cpu_thread = {
+	.store			= &posix_timer_task,
+	.thread_should_run	= posix_cpu_kthread_should_run,
+	.thread_fn		= posix_cpu_kthread_fn,
+	.thread_comm		= "posixcputmr/%u",
+	.setup			= posix_cpu_kthread_setup,
+	.park			= posix_cpu_kthread_park,
+	.unpark			= posix_cpu_kthread_unpark,
+};
+
+static int __init posix_cpu_thread_init(void)
+{
+	/* Start one for boot CPU. */
+	unsigned long cpu;
+	int ret;
+
+	/* init the per-cpu posix_timer_tasklets */
+	for_each_possible_cpu(cpu)
+		per_cpu(posix_timer_tasklist, cpu) = NULL;
+
+	ret = smpboot_register_percpu_thread(&posix_cpu_thread);
+	WARN_ON(ret);
+
+	return 0;
+}
+early_initcall(posix_cpu_thread_init);
+#else /* CONFIG_PREEMPT_RT_BASE */
+void run_posix_cpu_timers(struct task_struct *tsk)
+{
+	lockdep_assert_irqs_disabled();
+	__run_posix_cpu_timers(tsk);
+}
+#endif /* CONFIG_PREEMPT_RT_BASE */
+
 /*
  * Set one of the process-wide special case CPU timers or RLIMIT_CPU.
  * The tsk->sighand->siglock must be held by the caller.
@@ -1314,6 +1485,8 @@ static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
 		spin_unlock_irq(&timer.it_lock);
 
 		while (error == TIMER_RETRY) {
+
+			cpu_timers_grab_expiry_lock(&timer);
 			/*
 			 * We need to handle case when timer was or is in the
 			 * middle of firing. In other cases we already freed