Date: Tue, 24 Nov 2015 15:28:55 -0500
From: Tejun Heo <tj@kernel.org>
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>
Subject: Re: [PATCH v3 09/22] kthread: Allow to cancel kthread work
Message-ID: <20151124202855.GV17033@mtj.duckdns.org>
References: <1447853127-3461-1-git-send-email-pmladek@suse.com>
 <1447853127-3461-10-git-send-email-pmladek@suse.com>
 <20151123225823.GI19072@mtj.duckdns.org>
 <CA+55aFyW=hp-myZGcL+5r2x+fUbpBJLmxDY66QB5VQj-nNsCxQ@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CA+55aFyW=hp-myZGcL+5r2x+fUbpBJLmxDY66QB5VQj-nNsCxQ@mail.gmail.com>
User-Agent: Mutt/1.5.24 (2015-08-30)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 846
Lines: 26

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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/