From mboxrd@z Thu Jan 1 00:00:00 1970 From: Elias Oltmanns Subject: Re: [PATCH 2/4 v2] libata: Implement disk shock protection support Date: Fri, 19 Sep 2008 17:00:16 +0200 Message-ID: <87fxnwkwov.fsf@denkblock.local> References: <87d4j2n3dn.fsf@denkblock.local> <20080917163144.9870.97008.stgit@denkblock.local> <48D147E2.3020601@gmail.com> <87skrwmpng.fsf@denkblock.local> <48D3979F.10305@gmail.com> <87ljxokz67.fsf@denkblock.local> <48D3B3EE.70702@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from nebensachen.de ([195.34.83.29]:56559 "EHLO mail.nebensachen.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752897AbYISPB0 (ORCPT ); Fri, 19 Sep 2008 11:01:26 -0400 In-Reply-To: <48D3B3EE.70702@gmail.com> (Tejun Heo's message of "Fri, 19 Sep 2008 07:15:10 -0700") Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Tejun Heo Cc: Bartlomiej Zolnierkiewicz , Jeff Garzik , Randy Dunlap , linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org Tejun Heo wrote: > Elias Oltmanns wrote: >>> This should basically work but completion isn't really designed for > >>> this type of continuous events where single consumption should clear >>> all pending events. INIT_COMPLETION comes close but it doesn't lock, >>> so can't guarantee anything. What's necessary is the counterpart for >>> complete_all() for the wait. >> >> You are right that it isn't designed for this use case and my approach >> is somewhat hackish. Still, it really does exactly what we want. Please >> note that ap->park_req_pending is protected by the host lock; the call >> to complete() is atomic wrt the setting of ATA_EH_PARK for one of the >> devices on the port and so is the call to INIT_COMPLETION() wrt clearing >> ATA_EH_PARK requests for *all* devices on the port. >> >>> Well, anyways, I think the issue is slightly out of scope for this >>> patch and the only side effect is possibly looping over the do {} >>> while () block several times unnecessarily on certain cases, so I >>> think just noting about it should be enough for now. >>> >>> Can you please add explanation above wait_for_complete_timeout() that >>> all done counts should be cleared here but aren't and as a result the >>> loop might repeat determinate number of times unnecessarily and resend >>> as proper patch? >> >> Well, we don't really care about the done count after >> wait_for_completion_timeout() has returned. All that matters is that the >> done counter is cleared when all ATA_EH_PARK actions have been pulled in >> which happens at the start of each cycle over the loop. >> >> Perhaps I should add comments to this effect before >> wait_for_completion_timeout() as well as INIT_COMPLETION()? > > Ah... I missed the pull_park_action part. Yes, in that case, it's > correct now but I would really appreciate you explain amply what's > going on inside the pull function and why it's needed. Will do. By the way, it's just occurred to me that we really need to call complete_all() in ata_scsi_park_store(). So, thanks for making me think it all through once more. Regards, Elias