linux-kernel - Re: [rfc patch v4.4-rt2] sched: fix up preempt lazy forward port

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Date:	Fri, 22 Jan 2016 13:54:43 +0100
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	Grygorii Strashko <grygorii.strashko@...com>,
	Mike Galbraith <umgwanakikbuti@...il.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-rt-users <linux-rt-users@...r.kernel.org>
Subject: Re: [rfc patch v4.4-rt2] sched: fix up preempt lazy forward port

On 01/22/2016 12:58 PM, Grygorii Strashko wrote:
> On 01/18/2016 10:18 PM, Sebastian Andrzej Siewior wrote:
>> * Mike Galbraith | 2016-01-18 10:08:23 [+0100]:
>>
>>> --- a/arch/x86/entry/common.c
>>> +++ b/arch/x86/entry/common.c
>>> @@ -220,14 +220,14 @@ long syscall_trace_enter(struct pt_regs
>>>
>>> #define EXIT_TO_USERMODE_LOOP_FLAGS                \
>>>     (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE |    \
>>> -     _TIF_NEED_RESCHED | _TIF_USER_RETURN_NOTIFY)
>>> +     _TIF_NEED_RESCHED_MASK | _TIF_USER_RETURN_NOTIFY)
>>
>> If I read this right, the loop where this define is used
>> _TIF_ALLWORK_MASK in v4.1 of which _TIF_NEED_RESCHED_MASK was part of.
>> Adding this will reassmeble the old behaviour.
>> …
> 
> Just a question (sorry if dumb). ARM has _TIF_WORK_MASK defined:
> #define _TIF_WORK_MASK (_TIF_NEED_RESCHED | _TIF_SIGPENDING | \
>     _TIF_NOTIFY_RESUME | _TIF_UPROBE)
> 
> which is used to calculate loop exit condition in
>  do_work_pending() (arch/arm/kernel/signal.c).
> 
> Should _TIF_WORK_MASK also contain _TIF_NEED_RESCHED_LAZY?

Yes, and arm64 lacks the same bits.

Sebastian