From mboxrd@z Thu Jan  1 00:00:00 1970
From: Bart Van Assche <bart.vanassche@sandisk.com>
Subject: Re: [PATCH 6/6] multipathd: Remove a busy-waiting loop
Date: Wed, 17 Aug 2016 12:55:47 -0700
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To: Dragan Stancevic <dragan.stancevic@canonical.com>
Cc: device-mapper development <dm-devel@redhat.com>
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On 08/17/2016 12:42 PM, Dragan Stancevic wrote:
> Hi Bart-
>
> are the semantics below really safe, the don't appear to? Any caller of
> checker_thread_running is relaying on stale information. The
> c->thread_running could have changed as soon as you unlock.
>
> +static unsigned checker_thread_running(struct tur_checker_context *ct)
> +{
> +unsigned thread_running;
> +
> +pthread_spin_lock(&ct->hldr_lock);
> +thread_running = ct->thread_running;
> +pthread_spin_unlock(&ct->hldr_lock);
> +
> +return thread_running;
> +}

Hello Dragan,

If you have a look at libcheck_check() in tur.c then you will see that 
it is harmless if checker_thread_running() returns old information.

Bart.