linux-kernel - Re: [PATCH 4/4] vtime: No need to disable irqs on vtime

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Date:	Wed, 14 Nov 2012 20:41:19 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Tony Luck <tony.luck@...el.com>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: [PATCH 4/4] vtime: No need to disable irqs on vtime_account()

2012/11/14 Steven Rostedt <rostedt@...dmis.org>:
> On Wed, 2012-11-14 at 17:26 +0100, Frederic Weisbecker wrote:
>> vtime_account() is only called from irq entry. irqs
>> are always disabled at this point so we can safely
>> remove the irq disabling guards on that function.
>>
>> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
>> Cc: Peter Zijlstra <peterz@...radead.org>
>> Cc: Ingo Molnar <mingo@...nel.org>
>> Cc: Thomas Gleixner <tglx@...utronix.de>
>> Cc: Steven Rostedt <rostedt@...dmis.org>
>> Cc: Paul Gortmaker <paul.gortmaker@...driver.com>
>> Cc: Tony Luck <tony.luck@...el.com>
>> Cc: Fenghua Yu <fenghua.yu@...el.com>
>> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
>> Cc: Paul Mackerras <paulus@...ba.org>
>> Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
>> Cc: Heiko Carstens <heiko.carstens@...ibm.com>
>> ---
>>  kernel/sched/cputime.c |    6 ------
>>  1 files changed, 0 insertions(+), 6 deletions(-)
>>
>> diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
>> index 2e8d34a..80b2fd5 100644
>> --- a/kernel/sched/cputime.c
>> +++ b/kernel/sched/cputime.c
>> @@ -467,16 +467,10 @@ void vtime_task_switch(struct task_struct *prev)
>>  #ifndef __ARCH_HAS_VTIME_ACCOUNT
>>  void vtime_account(struct task_struct *tsk)
>>  {
>> -     unsigned long flags;
>> -
>> -     local_irq_save(flags);
>> -
>
> I'd add a WARN_ON_ONCE(!irqs_disabled()) again here, or is this also
> covered by the vtime_delta()?

Yeah it's the ending point for both vtime_account_system() and
vtime_account_idle()
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