linux-kernel - Re: [Priority Inheritance] SCHED_FIFO or SCHED

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Message-ID: <CAOVSwNEQzhzoKwnW5dZn8YsL5G+80_yvodmeJKBs2dSAxn7MsQ@mail.gmail.com>
Date:	Sat, 1 Oct 2011 22:29:04 +0200
From:	"Tadeus (Eus) Prastowo" <0x657573@...glemail.com>
To:	Mike Galbraith <efault@....de>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [Priority Inheritance] SCHED_FIFO or SCHED_RR?

On Sat, Oct 1, 2011 at 7:41 AM, Mike Galbraith <efault@....de> wrote:
> On Fri, 2011-09-30 at 21:12 +0200, Tadeus (Eus) Prastowo wrote:
>> > Why should a SCHED_NORMAL task inheriting the priority of a SCHED_RR
>> > task get the privilege of SCHED_FIFO task for running as long as it
>> > wishes even when the task giving the inheritance does not have such
>> > privilege?
>
> Existence of a critical section > slice would be the real problem, no?

No, it's not a problem because if a real-time system designer puts a
real-time task under SCHED_RR, he will calculate the length of the
critical section by taking into account the slice.

For the case of one SCHED_RR task sharing a critical section with one
SCHED_NORMAL task, the worst-case blocking time of the SCHED_RR task
is found by multiplying the critical section execution time taking
into account the slice by two.

>        -Mike

-- 
Eus
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