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    SubjectRe: [RFC PATCH 09/18] kthread: Make it easier to correctly sleep in iterant kthreads
    On Fri, 5 Jun 2015 18:10:21 +0200
    Peter Zijlstra <peterz@infradead.org> wrote:

    > On Fri, Jun 05, 2015 at 05:01:08PM +0200, Petr Mladek wrote:
    > > Many kthreads go into an interruptible sleep when there is nothing
    > > to do. They should check if anyone did not requested the kthread
    > > to terminate, freeze, or park in the meantime. It is easy to do
    > > it a wrong way.
    >
    > INTERRUPTIBLE is the wrong state to idle in for kthreads, use
    > TASK_IDLE.
    >
    > ---
    >
    > commit 80ed87c8a9ca0cad7ca66cf3bbdfb17559a66dcf
    > Author: Peter Zijlstra <peterz@infradead.org>
    > Date: Fri May 8 14:23:45 2015 +0200
    >
    > sched/wait: Introduce TASK_NOLOAD and TASK_IDLE
    >
    > Currently people use TASK_INTERRUPTIBLE to idle kthreads and wait for
    > 'work' because TASK_UNINTERRUPTIBLE contributes to the loadavg. Having
    > all idle kthreads contribute to the loadavg is somewhat silly.

    Not to mention, tasks in TASK_UNINTERRUPTIBLE state for too long will
    trigger hung task detection.


    >
    > Now mostly this works OK, because kthreads have all their signals
    > masked. However there's a few sites where this is causing problems and
    > TASK_UNINTERRUPTIBLE should be used, except for that loadavg issue.
    >
    > This patch adds TASK_NOLOAD which, when combined with
    > TASK_UNINTERRUPTIBLE avoids the loadavg accounting.
    >
    > As most of imagined usage sites are loops where a thread wants to
    > idle, waiting for work, a helper TASK_IDLE is introduced.
    >
    > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

    Acked-by: Steven Rostedt <rostedt@goodmis.org>

    -- Steve

    > Cc: Julian Anastasov <ja@ssi.bg>
    > Cc: Linus Torvalds <torvalds@linux-foundation.org>
    > Cc: NeilBrown <neilb@suse.de>
    > Cc: Oleg Nesterov <oleg@redhat.com>
    > Cc: Peter Zijlstra <peterz@infradead.org>
    > Cc: Thomas Gleixner <tglx@linutronix.de>
    > Signed-off-by: Ingo Molnar <mingo@kernel.org>
    >
    > diff --git a/include/linux/sched.h b/include/linux/sched.h


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