From mboxrd@z Thu Jan 1 00:00:00 1970 From: sboyd@codeaurora.org (Stephen Boyd) Date: Tue, 25 Nov 2014 17:27:38 -0800 Subject: [PATCH 3.18-rc3 v9 1/5] irqchip: gic: Finer grain locking for gic_raise_softirq In-Reply-To: <5474F05E.90401@linaro.org> References: <1415968543-29469-1-git-send-email-daniel.thompson@linaro.org> <1416936401-5147-1-git-send-email-daniel.thompson@linaro.org> <1416936401-5147-2-git-send-email-daniel.thompson@linaro.org> <5474BF19.3040707@arm.com> <5474F05E.90401@linaro.org> Message-ID: <54752C8A.1070006@codeaurora.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 11/25/2014 01:10 PM, Daniel Thompson wrote: > On 25/11/14 20:17, Nicolas Pitre wrote: >> On Tue, 25 Nov 2014, Marc Zyngier wrote: >> >>> Hi Daniel, >>> >>> On 25/11/14 17:26, Daniel Thompson wrote: >>>> irq_controller_lock is used for multiple purposes within the gic driver. >>>> Primarily it is used to make register read-modify-write sequences atomic. >>>> It is also used by gic_raise_softirq() in order that the big.LITTLE >>>> migration logic can figure out when it is safe to migrate interrupts >>>> between physical cores. >>>> >>>> The second usage of irq_controller_lock is difficult to discern when >>>> reviewing the code because the migration itself takes place outside >>>> the lock. >>>> >>>> This patch makes the second usage more explicit by splitting it out into >>>> a separate lock and providing better comments. >>> While we're at it, how about an additional patch that would make this >>> lock disappear entirely when the big-little stuff is not compiled in, >>> which is likely to be the case on a lot of (dare I say most?) systems? >>> That will save expensive barriers that we definitely could do without. >> For the record, I reviewed and ACKed a patch doing exactly that a while >> ago: >> >> http://lkml.org/lkml/2014/8/13/486 > Well remembered! That patch had a different motivation but is very > similar to mine... so much so I might steal bit of it. > > I'll make sure I put Stephen on Cc: when I respin with the changes Marc > requested. I don't get a random Cc here? :-) Anyway, yes please let's merge that patch. -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project