c7c2716139
[ Upstream commit 50d6b3cf9403879911e06d69c7ef41e43f8f7b4b ] If we have a kernel configured for periodic timer interrupts, and we have cpuidle enabled, then we end up with CPU1 losing timer interupts after a hotplug. This can manifest itself in RCU stall warnings, or userspace becoming unresponsive. The problem is that the kernel initially wants to use the TWD timer for interrupts, but the TWD loses context when we enter the C3 cpuidle state. Nothing reprograms the TWD after idle. We have solved this in the past by switching to broadcast timer ticks, and cpuidle44xx switches to that mode at boot time. However, there is nothing to switch from periodic mode local timers after a hotplug operation. We call tick_broadcast_enter() in omap_enter_idle_coupled(), which one would expect would take care of the issue, but internally this only deals with one-shot local timers - tick_broadcast_enable() on the other hand only deals with periodic local timers. So, we need to call both. Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk> [tony@atomide.com: just standardized the subject line] Signed-off-by: Tony Lindgren <tony@atomide.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.