linux-kernel - Re: [PATCH 4/7] ide: ide_hwgroup_t.rq doesn't need an ide

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 10 Oct 2008 12:17:06 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Elias Oltmanns <eo@...ensachen.de>
Cc:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/7] ide: ide_hwgroup_t.rq doesn't need an ide_lock held

On Fri, Oct 10 2008, Elias Oltmanns wrote:
> Jens Axboe <jens.axboe@...cle.com> wrote:
> > On Fri, Oct 10 2008, Elias Oltmanns wrote:
> >> Bartlomiej Zolnierkiewicz <bzolnier@...il.com> wrote:
> >
> >> > From: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
> >> > Subject: [PATCH] ide: ide_hwgroup_t.rq doesn't need an ide_lock held
> >> >
> >> > While at it:
> >> > - no need to check for hwgroup presence in ide_dump_opcode()
> >> >
> >> > Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
> >> > ---
> >> [...]
> >> > Index: b/drivers/ide/ide-io.c
> >> > ===================================================================
> >> > --- a/drivers/ide/ide-io.c
> >> > +++ b/drivers/ide/ide-io.c
> >> [...]
> >> > @@ -274,7 +269,11 @@ static void ide_complete_pm_request (ide
> >> >  		drive->dev_flags &= ~IDE_DFLAG_BLOCKED;
> >> >  		blk_start_queue(drive->queue);
> >> >  	}
> >> > -	HWGROUP(drive)->rq = NULL;
> >> > +	spin_unlock_irqrestore(&ide_lock, flags);
> >> > +
> >> > +	drive->hwif->hwgroup->rq = NULL;
> >> > +
> >> > +	spin_lock_irqsave(&ide_lock, flags);
> >> >  	if (__blk_end_request(rq, 0, 0))
> >> >  		BUG();
> >> >  	spin_unlock_irqrestore(&ide_lock, flags);
> >> 
> >> Is it really an improvement to release the lock here?
> >
> > And more importantly, is it even safe? What serializes ->rq assignments
> > and checks without the ide_lock? Looks fishy.
> 
> Well, I haven't quite made up my mind whether it'll work in all cases,
> but I think the hwgroup->busy flag is supposed to take care of that.

It used to be especially problematic with multi count IO, but my
knowledge and last check on that dates back to pre-2000 I think...

-- 
Jens Axboe

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/