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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: rmk@arm.linux.org.uk (Russell King)
Cc: dalecki@evision-ventures.com (Martin Dalecki),
	nconway.list@ukaea.org.uk (Neil Conway),
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] 2.5.15 IDE 61
Date: Tue, 14 May 2002 13:10:58 +0100 (BST)	[thread overview]
Message-ID: <E177b8s-0007lm-00@the-village.bc.nu> (raw)
In-Reply-To: <20020514123830.A18118@flint.arm.linux.org.uk> from "Russell King" at May 14, 2002 12:38:30 PM

> Something here smells fishy here - you shouldn't hold a spinlock for a long
> time (a long time === spinlocking, setting up the drive, possibly scheduling,

You can't hold it while scheduling or you may deadlock

> transferring data, getting status, then unlocking).  Also, remember,
> spinlocks are no-ops on uniprocessor systems.

Its possible it can be done with a semaphore but the whole business is
pretty tricky. IDE command processing occurs a fair bit at interrupt level
and you definitely don't want to block interrupts for long periods.

If the queue abstraction is right then the block layer should do all the
synchronization work that is required. It may cost a few cycles on the odd
case you can do overlapped command setup but that versus a nasty locking
mess its got to be better to lose those few cycles.

I don't even Martin here, the ide locking is currently utterly vile

  parent reply	other threads:[~2002-05-14 11:52 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-05-14  9:49 [PATCH] 2.5.15 IDE 61 Neil Conway
2002-05-14  8:52 ` Martin Dalecki
2002-05-14 10:12   ` Neil Conway
2002-05-14  9:30     ` Martin Dalecki
2002-05-14 11:10       ` Neil Conway
2002-05-14 10:21         ` Martin Dalecki
2002-05-14 11:38           ` Russell King
2002-05-14 10:49             ` Martin Dalecki
2002-05-14 12:10             ` Alan Cox [this message]
2002-05-14 11:11               ` Martin Dalecki
2002-05-14 12:47                 ` Alan Cox
2002-05-14 12:30                   ` Martin Dalecki
2002-05-15 14:43                 ` Pavel Machek
2002-05-14 12:00               ` Russell King
2002-05-14 11:03                 ` Martin Dalecki
2002-05-14 13:03               ` Neil Conway
2002-05-14 13:27                 ` Andre Hedrick
2002-05-14 14:45                 ` Alan Cox
2002-05-14 14:30                   ` Martin Dalecki
2002-05-14 16:20                     ` Neil Conway
2002-05-14 16:32                       ` Jens Axboe
2002-05-14 16:47                         ` Neil Conway
2002-05-14 16:51                           ` Jens Axboe
2002-05-15 11:37                             ` Neil Conway
2002-05-14 22:51                           ` Mike Fedyk
2002-05-14 16:26                     ` Jens Axboe
2002-05-14 19:34                     ` Anton Altaparmakov
2002-05-15  6:16                       ` Jens Axboe
2002-05-15  8:32                         ` Anton Altaparmakov
2002-05-15  9:42                           ` Martin Dalecki
2002-05-15  9:32                       ` Martin Dalecki
2002-05-15 11:44                         ` Neil Conway
2002-05-15 11:02                           ` Martin Dalecki
2002-05-15 13:10                             ` Alan Cox
2002-05-15 13:34                               ` Neil Conway
2002-05-15 13:04                                 ` Martin Dalecki
2002-05-15 14:08                               ` benh
2002-05-15 16:40                         ` Denis Vlasenko
2002-05-15 11:55                           ` Neil Conway
2002-05-17  7:07                             ` Mike Fedyk
2002-05-17 11:06                               ` Neil Conway
2002-05-17 10:12                                 ` Martin Dalecki
2002-05-14 16:03                   ` Neil Conway
2002-05-14 16:46                     ` Alan Cox
2002-05-14 12:52       ` Daniela Engert
  -- strict thread matches above, loose matches on Subject: below --
2002-05-06  3:53 Linux-2.5.14 Linus Torvalds
2002-05-13  9:48 ` [PATCH] 2.5.15 IDE 61 Martin Dalecki

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