linux-kernel - Re: [PATCH] Export current_is

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Message-ID: <adaejrdc34i.fsf@cisco.com>
Date:	Tue, 05 Dec 2006 15:52:13 -0800
From:	Roland Dreier <rdreier@...co.com>
To:	Andrew Morton <akpm@...l.org>
Cc:	Andy Fleming <afleming@...escale.com>,
	"Maciej W. Rozycki" <macro@...ux-mips.org>,
	Ben Collins <ben.collins@...ntu.com>,
	linux-kernel@...r.kernel.org, Linus Torvalds <torvalds@...l.org>,
	Jeff Garzik <jeff@...zik.org>
Subject: Re: [PATCH] Export current_is_keventd() for libphy

 > Ah.  The point is that the phy code doesn't want to flush _all_ pending
 > callbacks.  It only wants to flush its own one.  And its own one doesn't
 > take rtnl_lock().

OK, got it.  You're absolutely correct.

 > Maybe the lesson here is that flush_scheduled_work() is a bad function.
 > It should really be flush_this_work(struct work_struct *w).  That is in
 > fact what approximately 100% of the flush_scheduled_work() callers actually
 > want to do.

I think flush_this_work() runs into trouble if it means "make sure
everything up to <this work> has completed" because it still syncs
with everything before <this work>, which has the same risk of
deadlock.  And I'm not totally sure everyone who does
flush_scheduled_work() really means "cancel my work" -- they might mean
"finish up my work".

For example I would have to do some archeology to remember exactly
what I needed flush_scheduled_work() when I wrote drivers/infiniband/ulp/ipoib

 - R.
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