From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linus Torvalds Subject: Re: [PATCH 2/4] swait: add the missing killable swaits Date: Fri, 7 Jul 2017 12:58:26 -0700 Message-ID: References: <20170614222017.14653-1-mcgrof@kernel.org> <20170614222017.14653-3-mcgrof@kernel.org> <20170629125402.GH26046@kroah.com> <20170629133530.GA14747@kroah.com> <20170629174046.GC3954@linux-80c1.suse> <20170629183339.GD3954@linux-80c1.suse> <20170705020635.GD11168@linux-80c1.suse> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: <20170705020635.GD11168-3dK4OQgjB4rH06JGZaSw0A@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Davidlohr Bueso Cc: Thomas Gleixner , Greg KH , "Luis R. Rodriguez" , Martin Fuzzey , "Eric W. Biederman" , Dmitry Torokhov , Daniel Wagner , David Woodhouse , jewalt-d4N2ExZK1jaSe5ORCPIMD9BPR1lH4CV8@public.gmane.org, =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= , Arend Van Spriel , "Rafael J. Wysocki" , "Li, Yi" , atull-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, Moritz Fischer , Petr Mladek , Johannes Berg , Emmanuel Grumbach , "Coelho, Luciano" , Kal List-Id: linux-api@vger.kernel.org On Tue, Jul 4, 2017 at 7:06 PM, Davidlohr Bueso wrote: > > So here's something that boots and builds a kernel. Any thoughts? This patch ios just nasty crap. Sorry. It has random whitespace changfes that look entirely unrelated to trhe actual real meat of the patch, and that actually make whitespace *worse*. WHY? That alone should just mean that this patch needs to be thrown away and never ever looked at again. But also, this is fundamentally garbage. Exactly for the same reasons that the swait interfaces were fundamentally broken. It *looks* like it works on regular wait queues, and people can start using it that way, but it actually doesn't have the right semantics at all. The new "lockless" function ONLY works if you don't have a private wakeup function. So it completely changes the semantics of "wake_up_all()". It used to be that "wake_up_all()" did what the name suggested. With this patch, "wake_up_all()" will not cause random kernel oopses or memory corruption if you use any of the more specialized wakeup functions Guys, STOP DOING SHIT LIKE THIS! The swake interface was incredible crap, with bad semantics that confused people, and bad performance too. Don't make the normal wait-queues have similar idiotic problems. So no, this is not only NAK'ed, the whole approach is pure and utter shit and this needs to be buried deep and forgotten about so that it never ever comes back to life. Linus