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Date: Tue, 24 Nov 2015 15:28:55 -0500
From: Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH v3 09/22] kthread: Allow to cancel kthread work
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To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Petr Mladek <pmladek@suse.com>, Andrew Morton <akpm@linux-foundation.org>, Oleg Nesterov <oleg@redhat.com>, Ingo Molnar <mingo@redhat.com>, Peter Zijlstra <peterz@infradead.org>, Steven Rostedt <rostedt@goodmis.org>, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>, Josh Triplett <josh@joshtriplett.org>, Thomas Gleixner <tglx@linutronix.de>, Jiri Kosina <jkosina@suse.cz>, Borislav Petkov <bp@suse.de>, Michal Hocko <mhocko@suse.cz>, linux-mm <linux-mm@kvack.org>, Vlastimil Babka <vbabka@suse.cz>, Linux API <linux-api@vger.kernel.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>

Hello,

On Tue, Nov 24, 2015 at 12:23:53PM -0800, Linus Torvalds wrote:
> instead (possibly just "spin_unlock_wait()" - but the explicit loop

I see.  Wasn't thinking about cache traffic.  Yeah, spin_unlock_wait()
seems a lot better.

> might be worth it if you then want to check the "canceling" flag
> independently of the lock state too).
> 
> In general, it's very dangerous to try to cook up your own locking
> rules. People *always* get it wrong.

It's either trylock on timer side or timer active spinning trick on
canceling side, so this seems the lesser of the two evils.

Thanks.

-- 
tejun

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