From mboxrd@z Thu Jan 1 00:00:00 1970 From: mkl@pengutronix.de (Marc Kleine-Budde) Date: Thu, 20 Jun 2013 14:48:22 +0200 Subject: BUG: commit "ARM: Remove __ARCH_WANT_INTERRUPTS_ON_CTXSW on pre-ARMv6 CPUs" breaks armv5 with CONFIG_PREEMPT In-Reply-To: <51C2EBCD.4070206@pengutronix.de> References: <51C2C0B5.8020802@pengutronix.de> <20130620095705.GA18536@arm.com> <51C2D5EF.3040803@pengutronix.de> <20130620102856.GC18536@arm.com> <20130620111255.GD18536@arm.com> <51C2E917.9000708@pengutronix.de> <51C2EA04.4060701@pengutronix.de> <51C2EBCD.4070206@pengutronix.de> Message-ID: <51C2FA16.2080807@pengutronix.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 06/20/2013 01:47 PM, Marc Kleine-Budde wrote: > On 06/20/2013 01:39 PM, Marc Kleine-Budde wrote: >> On 06/20/2013 01:35 PM, Marc Kleine-Budde wrote: >>> On 06/20/2013 01:12 PM, Catalin Marinas wrote: >>>> On Thu, Jun 20, 2013 at 11:28:56AM +0100, Catalin Marinas wrote: >>>>> We may need to place the preempt disable/enable at a higher level in the >>>>> scheduler. My theory is that we have a context switch from prev to next. >>>>> We get preempted just before finish_arch_post_lock_switch(), so the MMU >>>>> hasn't been switched yet. The new switch during preemption happens to a >>>>> thread with the same next mm, so the scheduler no longer switch_mm() and >>>>> the TIF_SWITCH_MM isn't set for the new thread. >>>>> >>>>> I'll come back with another patch shortly. >>>> >>>> Here's another attempt (as before, only compile-tested): >>> >>> booting kernel from /image >>> zImage: concatenated oftree detected >>> booting Linux kernel with devicetree >>> >>> ...dead... >>> >>> Does every process have a "mm"? Even Kernel threads? > > I've added a check for "mm". Boots now and my test runs stable for 3 > minutes now. > > I'm not sure if we have to check for "mm" in > check_and_switch_context(), too. > > Thanks, > Marc > --- > > From 306d84d5f0645a86e86d539be0546c4ac758d3d4 Mon Sep 17 00:00:00 2001 > From: Catalin Marinas > Date: Thu, 20 Jun 2013 12:12:55 +0100 > Subject: [PATCH] arm: Fix deferred mm switch on VIVT processors > > As of commit b9d4d42ad9 (ARM: Remove __ARCH_WANT_INTERRUPTS_ON_CTXSW on > pre-ARMv6 CPUs), the mm switching on VIVT processors is done in the > finish_arch_post_lock_switch() function to avoid whole cache flushing > with interrupts disabled. The need for deferred mm switch is stored as a > thread flag (TIF_SWITCH_MM). However, with preemption enabled, we can > have another thread switch before finish_arch_post_lock_switch(). If the > new thread has the same mm as the previous 'next' thread, the scheduler > will not call switch_mm() and the TIF_SWITCH_MM flag won't be set for > the new thread. > > This patch moves the switch pending flag to the mm_context_t structure > since this is specific to the mm rather than thread. > > Signed-off-by: Catalin Marinas > Reported-by: Marc Kleine-Budde > [mkl: add check for mm] > Signed-off-by: Marc Kleine-Budde The test program works for 1 hour without problems. I'm going to push the patch to our customer, if it fixes the problem there, I'll add my Tested-by. regards, Marc -- Pengutronix e.K. | Marc Kleine-Budde | Industrial Linux Solutions | Phone: +49-231-2826-924 | Vertretung West/Dortmund | Fax: +49-5121-206917-5555 | Amtsgericht Hildesheim, HRA 2686 | http://www.pengutronix.de | -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 259 bytes Desc: OpenPGP digital signature URL: