linux-kernel - Re: SCHED

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Message-ID: <47904A27.4070405@sundmangroup.com>
Date:	Fri, 18 Jan 2008 07:41:43 +0100
From:	Matias Sundman <linux@...dmangroup.com>
To:	linux-kernel@...r.kernel.org
Subject: Re: SCHED_FIFO & system()

Hi,
I forgot to add one important detail - the Kernel is configured as - 
Preemptible Kernel (Low-Latency Desktop).

Cheers // Matias

linux@...dmangroup.com skrev:
> Hello,
> I have some strange behavior in one of my systems.
>
> I have a real-time kernel thread under SCHED_FIFO which is running every
> 10ms.
> It is blocking on a semaphore and released by a timer interrupt every 10ms.
> Generally this works really well.
>
> However, there is a module in the system that makes a / system() / call
> from c-code in user-space;
>
>   system("run_my_script");
>
> By calling and running a bash script. Independent of how the actual
> script looks like the real time kernel thread does not get scheduled under
> the time of 80ms -- the time it takes for the system() call to finish.
>
> I can see when running a LTT session that the wake_up event occurs for
> the real time thread 10ms into the system call but nevertheless the real
> time kernel thread does not get scheduled.
>
> The thread that calls system("run_my_script") is configured as SCHED_OTHER.
>
> The Kernel is 2.6.21.
>
>
> Anybody who recognize this or similar situations?
>
>
>
> Cheers // Matias
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