BUG: commit "ARM: Remove __ARCH_WANT_INTERRUPTS_ON_CTXSW on pre-ARMv6 CPUs" breaks armv5 with CONFIG_PREEMPT
From: mkl@pengutronix.de (Marc Kleine-Budde)
Date: 2013-06-21 10:28:48
On 06/20/2013 01:47 PM, Marc Kleine-Budde wrote:
On 06/20/2013 01:39 PM, Marc Kleine-Budde wrote:quoted
On 06/20/2013 01:35 PM, Marc Kleine-Budde wrote:quoted
On 06/20/2013 01:12 PM, Catalin Marinas wrote:quoted
On Thu, Jun 20, 2013 at 11:28:56AM +0100, Catalin Marinas wrote:quoted
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 <catalin.marinas@arm.com> 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 <catalin.marinas@arm.com> Reported-by: Marc Kleine-Budde <mkl@pengutronix.de> [mkl: add check for mm] Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Works on $CUSTOMERS's hardware. Tested-by: Marc Kleine-Budde <mkl@pengutronix.de> Catalin, do you take care of the patch? Please add stable on Cc. The fix is needed on kernels >= v3.5. 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: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20130621/1f4e3652/attachment.sig>