From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751818AbaILRH2 (ORCPT ); Fri, 12 Sep 2014 13:07:28 -0400 Received: from gw-1.arm.linux.org.uk ([78.32.30.217]:53325 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750881AbaILRH1 (ORCPT ); Fri, 12 Sep 2014 13:07:27 -0400 Date: Fri, 12 Sep 2014 18:07:20 +0100 From: Russell King - ARM Linux To: Daniel Thompson Cc: linaro-kernel@lists.linaro.org, patches@linaro.org, Catalin Marinas , linux-kernel@vger.kernel.org, John Stultz , Thomas Gleixner , Sumit Semwal , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 3.17-rc4 v5 2/6] arm: fiq: Replace default FIQ handler Message-ID: <20140912170720.GM12361@n2100.arm.linux.org.uk> References: <1410272111-30516-1-git-send-email-daniel.thompson@linaro.org> <1410435078-28462-1-git-send-email-daniel.thompson@linaro.org> <1410435078-28462-3-git-send-email-daniel.thompson@linaro.org> <20140912170307.GL12361@n2100.arm.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140912170307.GL12361@n2100.arm.linux.org.uk> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 12, 2014 at 06:03:07PM +0100, Russell King - ARM Linux wrote: > On Thu, Sep 11, 2014 at 12:31:14PM +0100, Daniel Thompson wrote: > > - .macro svc_entry, stack_hole=0 > > + .macro svc_entry, stack_hole=0, call_trace=1 > > UNWIND(.fnstart ) > > UNWIND(.save {r0 - pc} ) > > sub sp, sp, #(S_FRAME_SIZE + \stack_hole - 4) > > @@ -183,7 +183,9 @@ ENDPROC(__und_invalid) > > stmia r7, {r2 - r6} > > > > #ifdef CONFIG_TRACE_IRQFLAGS > > + .if \call_trace > > bl trace_hardirqs_off > > + .endif > > #endif > > Good, you picked this up from my patch. But what about the call into > lockdep from usr_entry? > > Yes, it should be safe if we're entering from user mode, because by > definition, the kernel can't be holding any locks at that point. > However, I'd much prefer to keep to a set of simple rules here: avoid > lockdep in FIQ code altogether. > > That's much easier to understand than "we can call into lockdep provided > we've been entered from user mode". > > The other thing you miss is that /potentially/ call into the scheduler > as well from a FIQ. Do we /really/ want to do that kind of work here? > > Not happy. And you're also missing a .cantunwind for __fiq_usr, which means that the Dwarf doesn't contain an explicit point to stop unwinding. Lastly, don't thread your new patches to the old ones. I utterly hate that behaviour. It makes subject lines totally pointless because all I end up seeing is "[PAT" on the very right hand of the screen. Far from useful. -- FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up according to speedtest.net.