Re: How to sleep a kernel thread?

From: Matthew Dharm (mdharm-kernel@one-eyed-alien.net)
Date: Sat Jun 03 2000 - 03:28:58 EDT

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    Is is safe to just set the task state myself?

    Spinlocks can give me mutual exclusion, but what I need to do is sleep
    until there is something in the queue to process. This is a textbook
    application of semaphores -- or is the kernel implementation of semaphores
    not so textbook?

    Matt Dharm

    On Sat, Jun 03, 2000 at 08:49:02AM +0200, Francis GALIEGUE wrote:
    > On Fri, 2 Jun 2000, Matthew Dharm wrote:
    >
    > > Hi! I'm working on the usb mass storage support for linux. For this, we
    > > have a kernel thread which blocks on a semaphore (used to indicate the
    > > number of commands in the queue).
    > >
    > > The problem is, when I block on the semaphore, the process is still marked
    > > as runnable, and thus drives the load average up to 1.00. How do I sleep
    > > so that I don't drive up the load? Or how do I mark the process as
    > > sleeping on a semaphore for the purposes of load average calculation?
    > >
    >
    > [ actually, I don't really know anything about kernel threads but ] my first
    > guess is that blocking on a semaphore from a kernel thread doesn't set the task
    > state to TASK_{UN,}INTERRUPTIBLE, this is why it keeps running.
    >
    > Can you use spinlocks in kernel threads? If yes, /methinks this is what you
    > should use. My $0.02. Indeed, I'd appreciate being corrected.
    >
    > --
    > fg
    >
    > "You can tune a filesystem but you can't tuna fish" (HP/UX' fsck manpage)
    >
    >
    >
    > -
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    -- 
Matthew Dharm                              Home: mdharm@one-eyed-alien.net 
Senior Engineer, QCP Inc.                            Work: mdharm@qcpi.com

    M:  No, Windows doesn't have any nag screens.
C:  Then what are those blue and white screens I get every day?
					-- Mike and Cobb
User Friendly, 1/4/1999

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