netdev - Re: question on pktgen shutdown logic.

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Message-ID: <1369264921.3301.370.camel@edumazet-glaptop>
Date:	Wed, 22 May 2013 16:22:01 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Ben Greear <greearb@...delatech.com>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: question on pktgen shutdown logic.

On Wed, 2013-05-22 at 16:15 -0700, Ben Greear wrote:
> While looking at pktgen.c in 3.9.3, I cannot explain how
> it does not race on shutdown.
> 
> The thread worker checks for pktgen_exiting, and will bail out
> of it's main loop and initiate cleanup if this is true.
> 
> The pg_net_exit sets the pktgen_exiting to true, and then
> proceedes to call
> 
> 		kthread_stop(t->tsk);
> 		kfree(t);
> 
> What I don't understand is what keeps the kfree(t) from happening
> before the thread has noticed pktgen_exiting is set and properly
> bailed out of it's loop and finished cleanup?

kthread_stop() is synchronous.



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