[PATCH] sched/cputime: correct account of irqtime

* [PATCH] sched/cputime: correct account of irqtime
@ 2020-10-12 13:50 Pingfan Liu
  2020-10-13  3:10 ` jun qian
  2020-10-14 13:02 ` Peter Zijlstra
  0 siblings, 2 replies; 5+ messages in thread
From: Pingfan Liu @ 2020-10-12 13:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Pingfan Liu, Ingo Molnar, Peter Zijlstra, Juri Lelli,
	Vincent Guittot, Dietmar Eggemann, Steven Rostedt, Ben Segall,
	Mel Gorman, Thomas Gleixner, Andy Lutomirski, Will Deacon,
	Paul E. McKenney, Frederic Weisbecker, Allen Pais, Romain Perier

__do_softirq() may be interrupted by hardware interrupts. In this case,
irqtime_account_irq() will account the time slice as CPUTIME_SOFTIRQ by
mistake.

By passing irqtime_account_irq() an extra param about either hardirq or
softirq, irqtime_account_irq() can handle the above case.

Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Will Deacon <will@kernel.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Allen Pais <allen.lkml@gmail.com>
Cc: Romain Perier <romain.perier@gmail.com>
To: linux-kernel@vger.kernel.org
---
 include/linux/hardirq.h |  4 ++--
 include/linux/vtime.h   | 12 ++++++------
 kernel/sched/cputime.c  |  4 ++--
 kernel/softirq.c        |  6 +++---
 4 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index 754f67a..56e7bb5 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -32,7 +32,7 @@ static __always_inline void rcu_irq_enter_check_tick(void)
  */
 #define __irq_enter()					\
 	do {						\
-		account_irq_enter_time(current);	\
+		account_irq_enter_time(current, true);	\
 		preempt_count_add(HARDIRQ_OFFSET);	\
 		lockdep_hardirq_enter();		\
 	} while (0)
@@ -63,7 +63,7 @@ void irq_enter_rcu(void);
 #define __irq_exit()					\
 	do {						\
 		lockdep_hardirq_exit();			\
-		account_irq_exit_time(current);		\
+		account_irq_exit_time(current, true);	\
 		preempt_count_sub(HARDIRQ_OFFSET);	\
 	} while (0)
 
diff --git a/include/linux/vtime.h b/include/linux/vtime.h
index 2cdeca0..294188ae1 100644
--- a/include/linux/vtime.h
+++ b/include/linux/vtime.h
@@ -98,21 +98,21 @@ static inline void vtime_flush(struct task_struct *tsk) { }
 
 
 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
-extern void irqtime_account_irq(struct task_struct *tsk);
+extern void irqtime_account_irq(struct task_struct *tsk, bool hardirq);
 #else
-static inline void irqtime_account_irq(struct task_struct *tsk) { }
+static inline void irqtime_account_irq(struct task_struct *tsk, bool hardirq) { }
 #endif
 
-static inline void account_irq_enter_time(struct task_struct *tsk)
+static inline void account_irq_enter_time(struct task_struct *tsk, bool hardirq)
 {
 	vtime_account_irq_enter(tsk);
-	irqtime_account_irq(tsk);
+	irqtime_account_irq(tsk, hardirq);
 }
 
-static inline void account_irq_exit_time(struct task_struct *tsk)
+static inline void account_irq_exit_time(struct task_struct *tsk, bool hardirq)
 {
 	vtime_account_irq_exit(tsk);
-	irqtime_account_irq(tsk);
+	irqtime_account_irq(tsk, hardirq);
 }
 
 #endif /* _LINUX_KERNEL_VTIME_H */
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 5a55d23..166f1d7 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -47,7 +47,7 @@ static void irqtime_account_delta(struct irqtime *irqtime, u64 delta,
  * Called before incrementing preempt_count on {soft,}irq_enter
  * and before decrementing preempt_count on {soft,}irq_exit.
  */
-void irqtime_account_irq(struct task_struct *curr)
+void irqtime_account_irq(struct task_struct *curr, bool hardirq)
 {
 	struct irqtime *irqtime = this_cpu_ptr(&cpu_irqtime);
 	s64 delta;
@@ -68,7 +68,7 @@ void irqtime_account_irq(struct task_struct *curr)
 	 */
 	if (hardirq_count())
 		irqtime_account_delta(irqtime, delta, CPUTIME_IRQ);
-	else if (in_serving_softirq() && curr != this_cpu_ksoftirqd())
+	else if (in_serving_softirq() && curr != this_cpu_ksoftirqd() && !hardirq)
 		irqtime_account_delta(irqtime, delta, CPUTIME_SOFTIRQ);
 }
 EXPORT_SYMBOL_GPL(irqtime_account_irq);
diff --git a/kernel/softirq.c b/kernel/softirq.c
index bf88d7f6..da59ea39 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -270,7 +270,7 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)
 	current->flags &= ~PF_MEMALLOC;
 
 	pending = local_softirq_pending();
-	account_irq_enter_time(current);
+	account_irq_enter_time(current, false);
 
 	__local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
 	in_hardirq = lockdep_softirq_start();
@@ -321,7 +321,7 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)
 	}
 
 	lockdep_softirq_end(in_hardirq);
-	account_irq_exit_time(current);
+	account_irq_exit_time(current, false);
 	__local_bh_enable(SOFTIRQ_OFFSET);
 	WARN_ON_ONCE(in_interrupt());
 	current_restore_flags(old_flags, PF_MEMALLOC);
@@ -417,7 +417,7 @@ static inline void __irq_exit_rcu(void)
 #else
 	lockdep_assert_irqs_disabled();
 #endif
-	account_irq_exit_time(current);
+	account_irq_exit_time(current, true);
 	preempt_count_sub(HARDIRQ_OFFSET);
 	if (!in_interrupt() && local_softirq_pending())
 		invoke_softirq();
-- 
2.7.5


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