On Mon, Jun 30, 2014 at 12:11:33PM -0700, Guenter Roeck wrote: > Various drivers implement architecture and/or device specific means > to restart (reset) the system. Various mechanisms have been implemented > to support those schemes. The best known mechanism is arm_pm_restart, > which is a function pointer to be set either from platform specific code > or from drivers. Another mechanism is to use hardware watchdogs to issue > a reset; this mechanism is used if there is no other method available > to reset a board or system. Two examples are alim7101_wdt, which currently > uses the reboot notifier to trigger a reset, and moxart_wdt, which registers > the arm_pm_restart function. > > The existing mechanisms have a number of drawbacks. Typically only one scheme > to restart the system is supported (at least if arm_pm_restart is used). > At least in theory there can be mutliple means to restart the system, some of > which may be less desirable (for example one mechanism may only reset the CPU, > while another may reset the entire system). Using arm_pm_restart can also be > racy if the function pointer is set from a driver, as the driver may be in > the process of being unloaded when arm_pm_restart is called. > Using the reboot notifier is always racy, as it is unknown if and when > other functions using the reboot notifier have completed execution > by the time the watchdog fires. > > To solve the problem, introduce a system restart notifier. This notifier > is expected to be called from the architecture specific machine_restart() > function. Drivers providing system restart functionality (such as the watchdog > drivers mentioned above) are expected to register with this notifier. > > Patch 1 of this series implements the notifier function. Patches 2 and 3 > implement calling the notifier chain from arm and arm64 restart code. > Patch 4 and 5 convert existing restart handlers in the watchdog subsystem > to use the restart notifier. Patch 6 unexports arm_pm_restart to ensure > that no one gets the idea to implement a restart handler as module. I think you need to restructure stuff somewhat, because I think you've missed drivers/power/reset/ entirely, or at least you've missed drivers/power/reset/restart-poweroff.c which calls arm_pm_restart directly. I'm not quite sure how we ended up with that... -- FTTC broadband for 0.8mile line: now at 9.7Mbps down 460kbps up... slowly improving, and getting towards what was expected from it. -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html