From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: David Woodhouse <dwmw2@infradead.org>
Cc: Greg Ungerer <gerg@snapgear.com>,
linux-kernel@vger.kernel.org,
David McCullough <davidm@snapgear.com>
Subject: Re: [PATCH]: uClinux (MMU-less) patches against 2.5.28
Date: 26 Jul 2002 18:27:58 +0100 [thread overview]
Message-ID: <1027704478.14660.66.camel@irongate.swansea.linux.org.uk> (raw)
In-Reply-To: <6881.1027699265@redhat.com>
On Fri, 2002-07-26 at 17:01, David Woodhouse wrote:
> What locks the page? Surely our write() implementation is just using
> copy_from_user(), to get the data from the user, and each erase and write
> to the flash chip can be considered atomic -- what's holding a lock, and
> what's causing the deadlock?
That is going to depend on the exact ordering that is done. You would
need to copy the user data into a temporary memory buffer (possibly
paging) then lock the flash write and restore.
Also a page can be locked because another I/O read is pending on it (ie
its already in someone elses read/page in handling and currently has
invalid data). You would need to be sure we never ended up with
deadlocks for any case where we have
process 1 copying page X from flash 2 to flash 1 page Y
process 2 copying page Y from flash 1 to flash 2 page X
With jffs2 and temporary buffering I guess it works out.
next prev parent reply other threads:[~2002-07-26 16:10 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-07-25 6:56 Greg Ungerer
2002-07-25 14:52 ` David Woodhouse
2002-07-26 0:08 ` Greg Ungerer
2002-07-26 1:20 ` Greg Ungerer
2002-07-26 8:19 ` David Woodhouse
2002-07-26 9:39 ` David Woodhouse
2002-07-26 9:58 ` David Woodhouse
2002-07-26 14:03 ` David Woodhouse
2002-07-26 16:01 ` David Woodhouse
2002-07-26 16:27 ` David Woodhouse
2002-07-26 17:27 ` Alan Cox [this message]
2002-07-26 17:11 ` Alan Cox
2002-07-26 14:50 ` Alan Cox
2002-07-26 10:56 ` Alan Cox
2002-07-26 10:39 ` Alan Cox
2002-07-26 15:08 ` gerg
2002-07-26 15:45 ` David Woodhouse
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