From mboxrd@z Thu Jan 1 00:00:00 1970 From: yong.zhang0@gmail.com (Yong Zhang) Date: Tue, 7 Feb 2012 20:34:55 +0800 Subject: [BUG] genirq: Race condition in ONESHOT IRQ handler disabling IRQ forever In-Reply-To: <20272.63074.235023.783459@ipc1.ka-ro> References: <20271.35831.227679.177366@ipc1.ka-ro> <20120207090305.GB32736@zhy> <20272.63074.235023.783459@ipc1.ka-ro> Message-ID: <20120207123455.GA2452@zhy> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, Feb 07, 2012 at 11:01:06AM +0100, Lothar Wa?mann wrote: > Hi, > > > On Mon, Feb 06, 2012 at 09:14:47AM +0100, Lothar Wa?mann wrote: > > > Hi, > > > > > > I already sent this to on Feb. 1, 2012 > > > but did not get any response there. So resending to a wider audience > > > with improved subject line: > > > > > > there is a race condition in the threaded IRQ handler code for oneshot > > > interrupts that may lead to disabling an IRQ indefinitely. IRQs are > > > masked before calling the hard-irq handler and are unmasked only after > > > the soft-irq handler has been run. Thus if the hard-irq handler > > > returns IRQ_HANDLED instead of IRQ_WAKE_THREAD, meaning the soft-irq > > > will not be called, the interrupt will remain masked forever. > > > > > > This can happen due to a short pulse on the interrupt line, that > > > triggers the interrupt logic, but goes undetected by the hard-irq > > > handler. The problem can be reproduced with the TSC2007 touch > > > controller driver that uses ONESHOT interrupts. > > > > Isn't it the responsibility of the driver (say TSC2007)? > > > > In this case, TSC2007 should return IRQ_WAKE_THREAD IMHO. > > > That would mean it had to return IRQ_WAKE_THREAD unconditionally > making the return code useless. > And it would cause an extra useless loop through the softirq > handler. Yeah, it's the default behavior when we introduce 'theadirqs', and it's safe. You know in your patch unmask_irq() is called locklessly and it will introduce other race. Thanks, Yong