From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx2-b.sourceforge.net ([10.3.1.92] helo=mail.sourceforge.net) by sc8-sf-list1.sourceforge.net with esmtp (Exim 4.30) id 1EIB8Y-0004BC-Lo for user-mode-linux-devel@lists.sourceforge.net; Wed, 21 Sep 2005 13:24:14 -0700 Received: from smtp004.mail.ukl.yahoo.com ([217.12.11.35]) by mail.sourceforge.net with smtp (Exim 4.44) id 1EIB8U-0005zR-Rs for user-mode-linux-devel@lists.sourceforge.net; Wed, 21 Sep 2005 13:24:14 -0700 From: Blaisorblade Subject: Re: [uml-devel] Re: [PATCH 07/10] uml: avoid fixing faults while atomic References: <200509211923.21861.blaisorblade@yahoo.it> <20050921172908.10219.57644.stgit@zion.home.lan> <20050921124957.437cf069.akpm@osdl.org> In-Reply-To: <20050921124957.437cf069.akpm@osdl.org> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200509212222.50653.blaisorblade@yahoo.it> Sender: user-mode-linux-devel-admin@lists.sourceforge.net Errors-To: user-mode-linux-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: The user-mode Linux development list List-Post: List-Help: List-Subscribe: , List-Archive: Date: Wed, 21 Sep 2005 22:22:50 +0200 To: user-mode-linux-devel@lists.sourceforge.net Cc: Andrew Morton , torvalds@osdl.org, jdike@addtoit.com, linux-kernel@vger.kernel.org On Wednesday 21 September 2005 21:49, Andrew Morton wrote: > "Paolo 'Blaisorblade' Giarrusso" wrote: > > From: Paolo 'Blaisorblade' Giarrusso > The in_atomic() test in x86's do_page_fault() is in fact a message passed > into it from filemap.c's kmap_atomic(). Ok, this can be ok, but: > It has accidental side-effects, > such as making copy_to_user() fail if inside spinlocks when > CONFIG_PREEMPT=y. Sorry, but should it ever succeed inside spinlocks? I mean, should it ever call down() inside spinlocks? (We never do down_trylock, and ever if we did the x86 trick, that wouldn't make the whole thing safe at all - they still take the spinlock and potentially sleep. And it's legal only if no spinlock is held). Even if spinlocks don't always trigger in_atomic() - which means that we'd need to have a better fix for this. (Btw, I took the above reasoning from something said, as an aside, on LWN.net kernel page, about the FUTEX deadlock on mm->mmap_sem of ~ 2.6.8 - yes, it wasn't the full truth, but not totally dumb). > So I think this change is only needed if UML implements kmap_atomic, as in > arch/i386/mm/highmem.c, which it surely does not do? NACK, see above. -- Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!". Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894) http://www.user-mode-linux.org/~blaisorblade ___________________________________ Yahoo! Mail: gratis 1GB per i messaggi e allegati da 10MB http://mail.yahoo.it ------------------------------------------------------- SF.Net email is sponsored by: Tame your development challenges with Apache's Geronimo App Server. Download it for free - -and be entered to win a 42" plasma tv or your very own Sony(tm)PSP. Click here to play: http://sourceforge.net/geronimo.php _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel