linux-kernel - Re: [PATCH v5 05/20] kthread: Add destroy_kthread

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Message-ID: <20160226151508.GG3305@pathway.suse.cz>
Date:	Fri, 26 Feb 2016 16:15:08 +0100
From:	Petr Mladek <pmladek@...e.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>, Tejun Heo <tj@...nel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Josh Triplett <josh@...htriplett.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jiri Kosina <jkosina@...e.cz>, Borislav Petkov <bp@...e.de>,
	Michal Hocko <mhocko@...e.cz>, linux-mm@...ck.org,
	Vlastimil Babka <vbabka@...e.cz>, linux-api@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 05/20] kthread: Add destroy_kthread_worker()

On Thu 2016-02-25 13:36:41, Peter Zijlstra wrote:
> On Mon, Feb 22, 2016 at 03:56:55PM +0100, Petr Mladek wrote:
> > Also note that drain() correctly handles self-queuing works in compare
> > with flush().
> 
> Nothing seems to prevent adding more work after drain() observes
> list_empty().

You might want to drain() more times during the kthread worker life
time to make sure that the work is done.

The user is responsible for stopping any queuing when this function
is called. The user usually needs to handle this anyway because
producing a work that could not be queued would cause problems.

To be honest, I wanted to keep the main principles of the API
compatible with workqueues. It should reduce some potential confusion.
Also it will make it easier to convert between the two APIs.
IMHO, there are work loads when you are not sure if you will
need a dedicated kthread when designing a new functionality.

Best Regards,
Petr