linux-kernel - Re: [PATCH] Export current_is

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Message-Id: <20061207101605.ba446f79.akpm@osdl.org>
Date:	Thu, 7 Dec 2006 10:16:05 -0800
From:	Andrew Morton <akpm@...l.org>
To:	Linus Torvalds <torvalds@...l.org>
Cc:	David Howells <dhowells@...hat.com>,
	"Maciej W. Rozycki" <macro@...ux-mips.org>,
	Roland Dreier <rdreier@...co.com>,
	Andy Fleming <afleming@...escale.com>,
	Ben Collins <ben.collins@...ntu.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jeff Garzik <jeff@...zik.org>
Subject: Re: [PATCH] Export current_is_keventd() for libphy

On Thu, 7 Dec 2006 10:01:56 -0800 (PST)
Linus Torvalds <torvalds@...l.org> wrote:

> 
> 
> On Thu, 7 Dec 2006, Andrew Morton wrote:
> > 
> > umm..  Putting a work_struct* into struct cpu_workqueue_struct and then
> > doing appropriate things with cpu_workqueue_struct.lock might work.
> 
> Yeah, that looks sane. We can't hide anything in "struct work", because we 
> can't trust it any more once it's been dispatched,

We _can_ trust it in the context of

	void flush_work(struct work_struct *work)

because the caller "owns" the work_struct.  It'd be pretty nutty for the
caller to pass in a pointer to something which could be freed at any time. 
Most flush_work_queue() callers do something like:


	flush_scheduled_work();
	kfree(my_object_which_contains_a_work_struct);

hopefully libphy follows that model...

> but adding a pointer to 
> the cpu_workqueue_struct that is only used to compare against another 
> pointer sounds fine.

ho-hum.  I'll take a look at turning that into something which compiles,
then I'll convert a few oft-used flush_scheduled_work() callers over to use
it.  To do this on a sensible timescale perhaps means that we should export
current_is_keventd(), get the howling hordes off our backs.

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