linux-kernel - Re: [PATCH] Export current_is

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Message-ID: <Pine.LNX.4.64.0612071022210.3615@woody.osdl.org>
Date:	Thu, 7 Dec 2006 10:27:10 -0800 (PST)
From:	Linus Torvalds <torvalds@...l.org>
To:	Andrew Morton <akpm@...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, Andrew Morton wrote:
> 
> We _can_ trust it in the context of
> 
> 	void flush_work(struct work_struct *work)

Yes, but the way the bits are defined, the "pending" bit is not meaningful 
as a synchronization event, for example - because _other_ users can't 
trust it once they've dispatched the function. So even in the synchronous 
run/flush_scheduled_work() kind of situation, you end up having to work 
with the fact that nobody _else_ can rely on the data structures, and that 
they are designed to work that way..

> 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.

Well, I simply committed my work that doesn't guarantee synchronization - 
the synchronization can now be added in kernel/workqueue.c any way we 
want. It's better than what we used to have, for sure, in both compiling 
and solving the practical problem, but also as a "go forward" point.

			Linus
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