Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753458AbaATLel (ORCPT ); Mon, 20 Jan 2014 06:34:41 -0500 Received: from merlin.infradead.org ([205.233.59.134]:54177 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750942AbaATLej (ORCPT ); Mon, 20 Jan 2014 06:34:39 -0500 Date: Mon, 20 Jan 2014 12:34:15 +0100 From: Peter Zijlstra To: "Nicholas A. Bellinger" Cc: target-devel , linux-kernel , Linus Torvalds , Ingo Molnar , Kent Overstreet , Jens Axboe Subject: Re: [PATCH-v2 1/3] percpu_ida: Make percpu_ida_alloc + callers accept task state bitmask Message-ID: <20140120113415.GE30183@twins.programming.kicks-ass.net> References: <1390189486-13579-1-git-send-email-nab@linux-iscsi.org> <1390189486-13579-2-git-send-email-nab@linux-iscsi.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1390189486-13579-2-git-send-email-nab@linux-iscsi.org> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 20, 2014 at 03:44:44AM +0000, Nicholas A. Bellinger wrote: > From: Kent Overstreet > > This patch changes percpu_ida_alloc() + callers to accept task state > bitmask for prepare_to_wait() for code like target/iscsi that needs > it for interruptible sleep, that is provided in a subsequent patch. > > It now expects TASK_UNINTERRUPTIBLE when the caller is able to sleep > waiting for a new tag, or TASK_RUNNING when the caller cannot sleep, > and is forced to return a negative value when no tags are available. > > v2 changes: > - Include blk-mq + tcm_fc + vhost/scsi + target/iscsi changes > - Drop signal_pending_state() call Urgh, you made me look at percpu_ida... steal_tags() does a for_each_cpus() with IRQs disabled. This mean you'll disable IRQs for multiple ticks on SGI class hardware. That is a _very_ long time indeed. Then there's alloc_global_tags() vs alloc_local_tags(), one gets an actual tag, while the other only moves tags about -- semantic mismatch. I do not get the comment near prepare to wait -- why does it matter if percpu_ida_free() flips a cpus_have_tags bit? Given I don't understand this comment, its hard for me to properly review the proposed patch series. Help? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/