linux-kernel - Re: [PATCH] Module : call synchronize_sched() between module exit() and free.

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Date:	Thu, 31 Jul 2008 10:54:33 +1000
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc:	"Frank Ch. Eigler" <fche@...hat.com>, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org
Subject: Re: [PATCH] Module : call synchronize_sched() between module exit() and free.

On Thursday 31 July 2008 00:09:38 Mathieu Desnoyers wrote:
> * Frank Ch. Eigler (fche@...hat.com) wrote:
> >(Would it not be desirable for an active marker to cause
> > module-foo's refcount to increase, so as to prevent unloading at this
> > time?)
>
> No, because I want to be able to unload the marked module and I don't
> want the fact that a probe is connected to it to change that.

Also you might want to put a marker in the module's exit code.

> Actually there is a detail missing here. Your teardown should be :
>  teardown() { ... marker_probe_unregister ("foo" , ..., &foo_handler );
>                   synchronize_sched(); /* Before returning from exit */ }
>
> This makes sure that every live marker call are finished and that it is
> safe to unload module-bar (the probe).

Perhaps create a synchronize_marker_unregister() wrapper for such uses; it's 
better documentation and the caller doesn't have to know exactly how it 
works...

Cheers,
Rusty.
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