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cputime: Safely read cputime of full dynticks CPUs

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While remotely reading the cputime of a task running in a
full dynticks CPU, the values stored in utime/stime fields
of struct task_struct may be stale. Its values may be those
of the last kernel <-> user transition time snapshot and
we need to add the tickless time spent since this snapshot.

To fix this, flush the cputime of the dynticks CPUs on
kernel <-> user transition and record the time / context
where we did this. Then on top of this snapshot and the current
time, perform the fixup on the reader side from task_times()
accessors.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
[fixed kvm module related build errors]
Signed-off-by: Sedat Dilek <sedat.dilek@gmail.com>
This commit is contained in:
Frederic Weisbecker
2012-12-16 20:00:34 +01:00
parent c11f11fcbd
commit 6a61671bb2
11 changed files with 292 additions and 54 deletions
Download Patch File Download Diff File Expand all files Collapse all files

47
include/linux/vtime.h
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@@ -8,35 +8,44 @@ extern void vtime_task_switch(struct task_struct *prev);
extern void vtime_account_system(struct task_struct *tsk);
extern void vtime_account_idle(struct task_struct *tsk);
extern void vtime_account_user(struct task_struct *tsk);
extern void vtime_account(struct task_struct *tsk);
extern void vtime_account_irq_enter(struct task_struct *tsk);
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
extern bool vtime_accounting_enabled(void);
#else
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
static inline bool vtime_accounting_enabled(void) { return true; }
#endif
#else /* !CONFIG_VIRT_CPU_ACCOUNTING */
static inline void vtime_task_switch(struct task_struct *prev) { }
static inline void vtime_account_system(struct task_struct *tsk) { }
static inline void vtime_account_user(struct task_struct *tsk) { }
static inline void vtime_account(struct task_struct *tsk) { }
static inline void vtime_account_irq_enter(struct task_struct *tsk) { }
static inline bool vtime_accounting_enabled(void) { return false; }
#endif
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
static inline void arch_vtime_task_switch(struct task_struct *tsk) { }
static inline void vtime_user_enter(struct task_struct *tsk)
{
vtime_account_system(tsk);
}
extern void arch_vtime_task_switch(struct task_struct *tsk);
extern void vtime_account_irq_exit(struct task_struct *tsk);
extern bool vtime_accounting_enabled(void);
extern void vtime_user_enter(struct task_struct *tsk);
static inline void vtime_user_exit(struct task_struct *tsk)
{
vtime_account_user(tsk);
}
extern void vtime_guest_enter(struct task_struct *tsk);
extern void vtime_guest_exit(struct task_struct *tsk);
extern void vtime_init_idle(struct task_struct *tsk);
#else
static inline void vtime_account_irq_exit(struct task_struct *tsk)
{
/* On hard|softirq exit we always account to hard|softirq cputime */
vtime_account_system(tsk);
}
static inline void vtime_user_enter(struct task_struct *tsk) { }
static inline void vtime_user_exit(struct task_struct *tsk) { }
static inline void vtime_guest_enter(struct task_struct *tsk) { }
static inline void vtime_guest_exit(struct task_struct *tsk) { }
static inline void vtime_init_idle(struct task_struct *tsk) { }
#endif
#ifdef CONFIG_IRQ_TIME_ACCOUNTING
@@ -45,25 +54,15 @@ extern void irqtime_account_irq(struct task_struct *tsk);
static inline void irqtime_account_irq(struct task_struct *tsk) { }
#endif
static inline void vtime_account_irq_enter(struct task_struct *tsk)
static inline void account_irq_enter_time(struct task_struct *tsk)
{
/*
* Hardirq can interrupt idle task anytime. So we need vtime_account()
* that performs the idle check in CONFIG_VIRT_CPU_ACCOUNTING.
* Softirq can also interrupt idle task directly if it calls
* local_bh_enable(). Such case probably don't exist but we never know.
* Ksoftirqd is not concerned because idle time is flushed on context
* switch. Softirqs in the end of hardirqs are also not a problem because
* the idle time is flushed on hardirq time already.
*/
vtime_account(tsk);
vtime_account_irq_enter(tsk);
irqtime_account_irq(tsk);
}
static inline void vtime_account_irq_exit(struct task_struct *tsk)
static inline void account_irq_exit_time(struct task_struct *tsk)
{
/* On hard|softirq exit we always account to hard|softirq cputime */
vtime_account_system(tsk);
vtime_account_irq_exit(tsk);
irqtime_account_irq(tsk);
}