From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Snitzer Subject: Re: [patch 2/4] swait: export the symbols __prepare_to_swait and __finish_swait Date: Tue, 22 May 2018 14:52:54 -0400 Message-ID: <20180522185037.GB25826@redhat.com> References: <20180519052503.325953342@debian.vm> <20180519052633.037700597@debian.vm> <20180522063425.GA7854@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20180522063425.GA7854@infradead.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: Christoph Hellwig Cc: peterz@infradead.org, wagi@monom.org, dm-devel@redhat.com, Mikulas Patocka , Dan Williams , tglx@linutronix.de List-Id: dm-devel.ids On Tue, May 22 2018 at 2:34am -0400, Christoph Hellwig wrote: > On Sat, May 19, 2018 at 07:25:05AM +0200, Mikulas Patocka wrote: > > In order to reduce locking overhead, I use the spinlock in > > swait_queue_head to protect not only the wait queue, but also the list of > > events. Consequently, I need to use unlocked functions __prepare_to_swait > > and __finish_swait. These functions are declared in the file > > include/linux/swait.h, but they are not exported, and so they are not > > useable from kernel modules. > > Please CC the author and maintainers of the swait code. > > My impression is that this is the wrong thing to do. The swait code > is supposed to be simple and self contained, and if you want to do > anything else use normal waitqueues. You said the same thing last time around. I've since cc'd Peter and Thomas and haven't heard back, see: https://www.redhat.com/archives/dm-devel/2018-May/msg00048.html The entire point of exporting these symbols is to allow use of the "simple waitqueue" code to optimize -- without resorting to using normal waitqueues. Mike