[PATCH 4/5] irqtime: Move irqtime entry accounting after irq offset incrementation
From: Frederic Weisbecker
Date: Wed Dec 02 2020 - 06:58:47 EST
IRQ time entry is currently accounted before HARDIRQ_OFFSET or
SOFTIRQ_OFFSET are incremented. This is convenient to decide to which
index the cputime to account is dispatched.
Unfortunately it prevents tick_irq_enter() from being called under
HARDIRQ_OFFSET because tick_irq_enter() has to be called before the IRQ
entry accounting due to the necessary clock catch up. As a result we
don't benefit from appropriate lockdep coverage on tick_irq_enter().
To prepare for fixing this, move the IRQ entry cputime accounting after
the preempt offset is incremented. This requires the cputime dispatch
code to handle the extra offset.
Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
---
include/linux/hardirq.h | 4 ++--
include/linux/vtime.h | 34 ++++++++++++++++++++++++----------
kernel/sched/cputime.c | 18 +++++++++++-------
kernel/softirq.c | 6 +++---
4 files changed, 40 insertions(+), 22 deletions(-)
diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index 754f67ac4326..7c9d6a2d7e90 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -32,9 +32,9 @@ static __always_inline void rcu_irq_enter_check_tick(void)
*/
#define __irq_enter() \
do { \
- account_irq_enter_time(current); \
preempt_count_add(HARDIRQ_OFFSET); \
lockdep_hardirq_enter(); \
+ account_hardirq_enter(current); \
} while (0)
/*
@@ -62,8 +62,8 @@ void irq_enter_rcu(void);
*/
#define __irq_exit() \
do { \
+ account_hardirq_exit(current); \
lockdep_hardirq_exit(); \
- account_irq_exit_time(current); \
preempt_count_sub(HARDIRQ_OFFSET); \
} while (0)
diff --git a/include/linux/vtime.h b/include/linux/vtime.h
index 6c9867419615..041d6524d144 100644
--- a/include/linux/vtime.h
+++ b/include/linux/vtime.h
@@ -83,32 +83,46 @@ static inline void vtime_init_idle(struct task_struct *tsk, int cpu) { }
#endif
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
-extern void vtime_account_irq(struct task_struct *tsk);
+extern void vtime_account_irq(struct task_struct *tsk, unsigned int offset);
extern void vtime_account_softirq(struct task_struct *tsk);
extern void vtime_account_hardirq(struct task_struct *tsk);
extern void vtime_flush(struct task_struct *tsk);
#else /* !CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
-static inline void vtime_account_irq(struct task_struct *tsk) { }
+static inline void vtime_account_irq(struct task_struct *tsk, unsigned int offset) { }
+static inline void vtime_account_softirq(struct task_struct *tsk) { }
+static inline void vtime_account_hardirq(struct task_struct *tsk) { }
static inline void vtime_flush(struct task_struct *tsk) { }
#endif
#ifdef CONFIG_IRQ_TIME_ACCOUNTING
-extern void irqtime_account_irq(struct task_struct *tsk);
+extern void irqtime_account_irq(struct task_struct *tsk, unsigned int offset);
#else
-static inline void irqtime_account_irq(struct task_struct *tsk) { }
+static inline void irqtime_account_irq(struct task_struct *tsk, unsigned int offset) { }
#endif
-static inline void account_irq_enter_time(struct task_struct *tsk)
+static inline void account_softirq_enter(struct task_struct *tsk)
{
- vtime_account_irq(tsk);
- irqtime_account_irq(tsk);
+ vtime_account_irq(tsk, SOFTIRQ_OFFSET);
+ irqtime_account_irq(tsk, SOFTIRQ_OFFSET);
}
-static inline void account_irq_exit_time(struct task_struct *tsk)
+static inline void account_softirq_exit(struct task_struct *tsk)
{
- vtime_account_irq(tsk);
- irqtime_account_irq(tsk);
+ vtime_account_softirq(tsk);
+ irqtime_account_irq(tsk, 0);
+}
+
+static inline void account_hardirq_enter(struct task_struct *tsk)
+{
+ vtime_account_irq(tsk, HARDIRQ_OFFSET);
+ irqtime_account_irq(tsk, HARDIRQ_OFFSET);
+}
+
+static inline void account_hardirq_exit(struct task_struct *tsk)
+{
+ vtime_account_hardirq(tsk);
+ irqtime_account_irq(tsk, 0);
}
#endif /* _LINUX_KERNEL_VTIME_H */
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 02163d4260d7..5f611658eeab 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -44,12 +44,13 @@ static void irqtime_account_delta(struct irqtime *irqtime, u64 delta,
}
/*
- * Called before incrementing preempt_count on {soft,}irq_enter
+ * Called after 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, unsigned int offset)
{
struct irqtime *irqtime = this_cpu_ptr(&cpu_irqtime);
+ unsigned int pc;
s64 delta;
int cpu;
@@ -59,6 +60,7 @@ void irqtime_account_irq(struct task_struct *curr)
cpu = smp_processor_id();
delta = sched_clock_cpu(cpu) - irqtime->irq_start_time;
irqtime->irq_start_time += delta;
+ pc = preempt_count() - offset;
/*
* We do not account for softirq time from ksoftirqd here.
@@ -66,9 +68,9 @@ void irqtime_account_irq(struct task_struct *curr)
* in that case, so as not to confuse scheduler with a special task
* that do not consume any time, but still wants to run.
*/
- if (hardirq_count())
+ if (pc & HARDIRQ_MASK)
irqtime_account_delta(irqtime, delta, CPUTIME_IRQ);
- else if (in_serving_softirq() && curr != this_cpu_ksoftirqd())
+ else if ((pc & SOFTIRQ_OFFSET) && curr != this_cpu_ksoftirqd())
irqtime_account_delta(irqtime, delta, CPUTIME_SOFTIRQ);
}
@@ -417,11 +419,13 @@ void vtime_task_switch(struct task_struct *prev)
}
# endif
-void vtime_account_irq(struct task_struct *tsk)
+void vtime_account_irq(struct task_struct *tsk, unsigned int offset)
{
- if (hardirq_count()) {
+ unsigned int pc = preempt_count() - offset;
+
+ if (pc & HARDIRQ_OFFSET) {
vtime_account_hardirq(tsk);
- } else if (in_serving_softirq()) {
+ } else if (pc & SOFTIRQ_OFFSET) {
vtime_account_softirq(tsk);
} else if (!IS_ENABLED(CONFIG_HAVE_VIRT_CPU_ACCOUNTING_IDLE) &&
is_idle_task(tsk)) {
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 617009ccd82c..b8f42b3ba8ca 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -315,10 +315,10 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)
current->flags &= ~PF_MEMALLOC;
pending = local_softirq_pending();
- account_irq_enter_time(current);
__local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
in_hardirq = lockdep_softirq_start();
+ account_softirq_enter(current);
restart:
/* Reset the pending bitmask before enabling irqs */
@@ -365,8 +365,8 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)
wakeup_softirqd();
}
+ account_softirq_exit(current);
lockdep_softirq_end(in_hardirq);
- account_irq_exit_time(current);
__local_bh_enable(SOFTIRQ_OFFSET);
WARN_ON_ONCE(in_interrupt());
current_restore_flags(old_flags, PF_MEMALLOC);
@@ -418,7 +418,7 @@ static inline void __irq_exit_rcu(void)
#else
lockdep_assert_irqs_disabled();
#endif
- account_irq_exit_time(current);
+ account_hardirq_exit(current);
preempt_count_sub(HARDIRQ_OFFSET);
if (!in_interrupt() && local_softirq_pending())
invoke_softirq();
--
2.25.1