linux-kernel - [patch V3 1/3] posix-cpu-timers: Split run_posix_cpu

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Date:   Thu, 30 Jul 2020 12:14:05 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, Oleg Nesterov <oleg@...hat.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        John Stultz <john.stultz@...aro.org>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [patch V3 1/3] posix-cpu-timers: Split run_posix_cpu_timers()

From: Thomas Gleixner <tglx@...utronix.de>

Split it up as a preparatory step to move the heavy lifting out of
interrupt context.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

---
 kernel/time/posix-cpu-timers.c |   43 ++++++++++++++++++++++-------------------
 1 file changed, 24 insertions(+), 19 deletions(-)

--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -1080,32 +1080,15 @@ static inline bool fastpath_timer_check(
 	return false;
 }
 
-/*
- * 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(void)
+static void __run_posix_cpu_timers(struct task_struct *tsk)
 {
-	struct task_struct *tsk = current;
 	struct k_itimer *timer, *next;
 	unsigned long flags;
 	LIST_HEAD(firing);
 
-	lockdep_assert_irqs_disabled();
-
-	/*
-	 * The fast path checks that there are no expired thread or thread
-	 * group timers.  If that's so, just return.
-	 */
-	if (!fastpath_timer_check(tsk))
+	if (!lock_task_sighand(tsk, &flags))
 		return;
 
-	lockdep_posixtimer_enter();
-	if (!lock_task_sighand(tsk, &flags)) {
-		lockdep_posixtimer_exit();
-		return;
-	}
 	/*
 	 * Here we take off tsk->signal->cpu_timers[N] and
 	 * tsk->cpu_timers[N] all the timers that are firing, and
@@ -1147,6 +1130,28 @@ void run_posix_cpu_timers(void)
 			cpu_timer_fire(timer);
 		spin_unlock(&timer->it_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(void)
+{
+	struct task_struct *tsk = current;
+
+	lockdep_assert_irqs_disabled();
+
+	/*
+	 * The fast path checks that there are no expired thread or thread
+	 * group timers.  If that's so, just return.
+	 */
+	if (!fastpath_timer_check(tsk))
+		return;
+
+	lockdep_posixtimer_enter();
+	__run_posix_cpu_timers(tsk);
 	lockdep_posixtimer_exit();
 }