The HyperNews Linux KHG Discussion Pages

Feedback: SCHED_FIFO scheduling

Forum: The Linux Kernel Hackers' Guide
Re: Question Realtime Problem (Uwe Gaethke)
Date: Thu, 15 Jan 1998 00:41:30 GMT
From: Balaji Srinivasan <>

I have a question regarding your initial query.

In your mail you said that the expected sequence of events is: 1: The task calls 'read' 2: RTC generates an interrupt 3: The task returns from read.

I dont understand why the task should wait till the rtc generates an interrupt. Am i missing something here?

As far as your query goes: What might be happening is that ps/free might be waking up some other SCHED_FIFO (which i guess is what you are using) scheduled process (some kernel threads are scheduled using SCHED_FIFO). This might schedule that process in instead of yours.

If you need predictable performance then you might try using KURT: KU Real-Time Linux (

I hope this helps balaji