From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Lord Subject: Re: [PATCH 1/11] Add generic helpers for arch IPI function calls Date: Wed, 23 Apr 2008 10:46:49 -0400 Message-ID: <480F4BD9.8090003@rtr.ca> References: <1208851058-8500-1-git-send-email-jens.axboe@oracle.com> <1208851058-8500-2-git-send-email-jens.axboe@oracle.com> <480E70ED.3030701@rtr.ca> <20080423072432.GX12774@kernel.dk> <480F3CBC.60305@rtr.ca> <20080423135110.GO12774@kernel.dk> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20080423135110.GO12774@kernel.dk> Sender: linux-kernel-owner@vger.kernel.org To: Jens Axboe Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, npiggin@suse.de, torvalds@linux-foundation.org List-Id: linux-arch.vger.kernel.org Jens Axboe wrote: > On Wed, Apr 23 2008, Mark Lord wrote: >.. >> The second bug, is that for the halt case at least, >> nobody waits for the other CPU to actually halt >> before continuing.. so we sometimes enter the shutdown >> code while other CPUs are still active. >> >> This causes some machines to hang at shutdown, >> unless CPU_HOTPLUG is configured and takes them offline >> before we get here. > > I'm guessing there's a reason it doesn't pass '1' as the last argument, > because that would fix that issue? .. Undoubtedly -- perhaps the called CPU halts, and therefore cannot reply. :) But some kind of pre-halt ack, perhaps plus a short delay by the caller after receipt of the ack, would probably suffice to kill that bug. But I really haven't studied this code enough to know, other than that it historically has been a sticky area to poke around in. Cheers