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[220.235.108.194]) by smtp.gmail.com with ESMTPSA id j2sm5103971pjy.1.2020.06.25.03.01.29 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Thu, 25 Jun 2020 03:01:31 -0700 (PDT) Date: Thu, 25 Jun 2020 18:01:26 +0800 From: Kent Gibson To: Bartosz Golaszewski Cc: LKML , linux-gpio , Linus Walleij Subject: Re: [PATCH 08/22] gpiolib: cdev: complete the irq/thread timestamp handshake Message-ID: <20200625100126.GA18788@sol> References: <20200623040107.22270-1-warthog618@gmail.com> <20200623040107.22270-9-warthog618@gmail.com> <20200624140806.GA7569@sol> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-gpio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org On Thu, Jun 25, 2020 at 11:44:30AM +0200, Bartosz Golaszewski wrote: > On Wed, Jun 24, 2020 at 4:08 PM Kent Gibson wrote: > > > > On Wed, Jun 24, 2020 at 04:00:42PM +0200, Bartosz Golaszewski wrote: > > > wt., 23 cze 2020 o 06:02 Kent Gibson napisał(a): [ snip ] > > > > I'm not totally sure myself, as my understanding of how interrupts are > > shared in the kernel is pretty sketchy, but my concern is that if we > > are sharing the irq then whoever we are sharing with may release the irq > > and we go from nested to unnested. Or vice versa. Not sure if that is > > valid, but that was my concern, and it seemed like a minor change to > > cover it just in case. > > > > It's my understanding that a shared interrupt must be explicitly > requested as shared by all previous users or request_irq() will fail. > In this case: we call request_threaded_irq() without the IRQF_SHARED > flag so it's never a shared interrupt. Even if someone previously > requested it as shared - our call will simply fail. > OK. Is there a reason not to share the interrupt? > I still think that resetting the timestamp is fine because it's not > being set to 0 in hardirq context. We just need a different > explanation. > Or just drop it? Cheers, Kent.