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Date: Thu, 21 May 2020 07:05:44 +0530 From: Pavan Kondeti <pkondeti@...eaurora.org> To: Greg Kroah-Hartman <gregkh@...uxfoundation.org> Cc: linux-kernel@...r.kernel.org, Vinayak Menon <vinmenon@...eaurora.org>, Ben Dooks <ben.dooks@...ethink.co.uk>, "Peter Zijlstra (Intel)" <peterz@...radead.org>, Thomas Gleixner <tglx@...utronix.de>, "Steven Rostedt (VMware)" <rostedt@...dmis.org>, Liang Chen <cl@...k-chips.com> Subject: Re: [PATCH] kthread: Use TASK_IDLE state for newly created kernel threads On Wed, May 20, 2020 at 08:18:58PM +0200, Greg Kroah-Hartman wrote: > On Wed, May 20, 2020 at 05:25:09PM +0530, Pavankumar Kondeti wrote: > > When kernel threads are created for later use, they will be in > > TASK_UNINTERRUPTIBLE state until they are woken up. This results > > in increased loadavg and false hung task reports. To fix this, > > use TASK_IDLE state instead of TASK_UNINTERRUPTIBLE when > > a kernel thread schedules out for the first time. > > > > Signed-off-by: Pavankumar Kondeti <pkondeti@...eaurora.org> > > --- > > kernel/kthread.c | 6 +++--- > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/kernel/kthread.c b/kernel/kthread.c > > index bfbfa48..b74ed8e 100644 > > --- a/kernel/kthread.c > > +++ b/kernel/kthread.c > > @@ -250,7 +250,7 @@ static int kthread(void *_create) > > current->vfork_done = &self->exited; > > > > /* OK, tell user we're spawned, wait for stop or wakeup */ > > - __set_current_state(TASK_UNINTERRUPTIBLE); > > + __set_current_state(TASK_IDLE); > > create->result = current; > > /* > > * Thread is going to call schedule(), do not preempt it, > > @@ -428,7 +428,7 @@ static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state) > > > > void kthread_bind_mask(struct task_struct *p, const struct cpumask *mask) > > { > > - __kthread_bind_mask(p, mask, TASK_UNINTERRUPTIBLE); > > + __kthread_bind_mask(p, mask, TASK_IDLE); > > } > > > > /** > > @@ -442,7 +442,7 @@ void kthread_bind_mask(struct task_struct *p, const struct cpumask *mask) > > */ > > void kthread_bind(struct task_struct *p, unsigned int cpu) > > { > > - __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE); > > + __kthread_bind(p, cpu, TASK_IDLE); > > } > > EXPORT_SYMBOL(kthread_bind); > > It's as if people never read mailing lists: > https://lore.kernel.org/r/DM6PR11MB3531D3B164357B2DC476102DDFC90@DM6PR11MB3531.namprd11.prod.outlook.com > > Given that this is an identical resend of the previous patch, why are > you doing so, and what has changed since that original rejection? > I did not know that it is attempted before. Thanks for pointing to the previous discussion. We have seen hung task reports from customers and it is due to a downstream change which create bunch of kernel threads for later use. From Peter's reply, I understood that one must wake up the kthread after creation and put it in INTERRUPTIBLE sleep. I will pass on the message. Thanks, Pavan -- Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.
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