From: Stefan Richter <stefanr@s5r6.in-berlin.de>
To: linux1394-devel@lists.sourceforge.net
Cc: linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 2.6.17-mm1 4/3] ieee1394: convert ieee1394_transactions from semaphores to waitqueue
Date: Sun, 25 Jun 2006 19:27:16 +0200 [thread overview]
Message-ID: <449EC774.5060908@s5r6.in-berlin.de> (raw)
In-Reply-To: <tkrat.3f9c07538e381afd@s5r6.in-berlin.de>
I wrote on 2006-06-24:
> + return wait_event_interruptible(tlabel_wq,
> + !hpsb_get_tlabel_atomic(packet));
Hmm. "Linux Device Drivers" says about wait_event_interruptible(wq,
condition): ''Note that @condition may be evaluated an arbitrary number
of times, so it should not have any side effects.''
Alas the hpsb_get_tlabel_atomic() _does_ have a side effect, but only
when !hpsb_get_tlabel_atomic(packet) is true.
The current implementation of wait_event_interruptible() seems to
evaluate @condition multiple times if it is false but only _once_ while
it is true. May I rely on this fact or do I have to rewrite the
condition to be completely free of side effects?
I don't believe there would be ever a sensible implementation of
wait_event_interruptible() which would evaluate @condition again after
it became true.
Thanks,
--
Stefan Richter
-=====-=-==- -==- ==--=
http://arcgraph.de/sr/
prev parent reply other threads:[~2006-06-25 17:28 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <449BEBFB.60302@s5r6.in-berlin.de>
[not found] ` <200606230904.k5N94Al3005245@shell0.pdx.osdl.net>
[not found] ` <30866.1151072338@warthog.cambridge.redhat.com>
[not found] ` <tkrat.df6845846c72176e@s5r6.in-berlin.de>
2006-06-24 9:32 ` [RFC PATCH 2.6.17-mm1 1/3] ieee1394: reduce size of hpsb_host by 252 bytes Stefan Richter
2006-06-24 9:33 ` [RFC PATCH 2.6.17-mm1 2/3] ieee1394: coarser locking for tlabel allocation Stefan Richter
2006-06-24 9:35 ` [RFC PATCH 2.6.17-mm1 3/3] ieee1394: nodemgr: read tlabel attributes atomically Stefan Richter
2006-06-24 17:32 ` [RFC PATCH 2.6.17-mm1 4/3] ieee1394: convert ieee1394_transactions from semaphores to waitqueue Stefan Richter
2006-06-24 17:45 ` Stefan Richter
2006-06-24 18:12 ` Arjan van de Ven
2006-06-24 20:28 ` Stefan Richter
2006-06-24 20:56 ` Stefan Richter
2006-06-25 19:37 ` [RFC PATCH 2.6.17-mm1 5/3] ieee1394: raw1394: remove redundant counting semaphore Stefan Richter
2006-06-25 19:54 ` Stefan Richter
2006-06-25 17:27 ` Stefan Richter [this message]
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