Re: [RFC PATCH 09/18] kthread: Make it easier to correctly sleep in iterant kthreads
From: Steven Rostedt <hidden>
Date: 2015-06-08 17:48:22
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On Fri, 5 Jun 2015 18:10:21 +0200 Peter Zijlstra [off-list ref] wrote:
On Fri, Jun 05, 2015 at 05:01:08PM +0200, Petr Mladek wrote:quoted
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 [off-list ref] 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) [off-list ref]Acked-by: Steven Rostedt <redacted> -- Steve
quoted hunk ↗ jump to hunk
Cc: Julian Anastasov [off-list ref] Cc: Linus Torvalds [off-list ref] Cc: NeilBrown [off-list ref] Cc: Oleg Nesterov [off-list ref] Cc: Peter Zijlstra [off-list ref] Cc: Thomas Gleixner [off-list ref] Signed-off-by: Ingo Molnar [off-list ref]diff --git a/include/linux/sched.h b/include/linux/sched.h