From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Sat, 29 Sep 2007 15:08:36 +0200 From: Nick Piggin Subject: Re: [patch] splice mmap_sem deadlock Message-ID: <20070929130836.GB14159@wotan.suse.de> References: <20070928160035.GD12538@wotan.suse.de> <20070928173144.GA11717@kernel.dk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org Return-Path: To: Linus Torvalds Cc: Jens Axboe , Andrew Morton , Linux Memory Management List List-ID: On Fri, Sep 28, 2007 at 11:10:34AM -0700, Linus Torvalds wrote: > > > On Fri, 28 Sep 2007, Jens Axboe wrote: > > > > It does looks suspicious. It was actually Linus who originally suggested > > this approach and wrote that comment - Linus? > > Well, it used to be true, long time ago. It probably was still true in the > original splice patch back way back when. But yeah, rwsemaphores broke > that (very useful) trick in the name of fairness ;( You might be thinking about rwlocks as well, where it still is true AFAIK. The rwsem fairness I think is pretty critical for it's most prominent consumer (ie. mmap_sem), because read sides can be very long and frequent with a lot of concurrency (it would be easy to starve the write side). -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org