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authorGuenter Roeck <linux@roeck-us.net>2014-09-26 00:03:16 +0000
committerGuenter Roeck <linux@roeck-us.net>2014-09-26 00:00:06 -0700
commitb63adb979583ef185718d774d8162387db5589c0 (patch)
treee6467352881135f82037829ecdd204489fbad415 /include/linux/reboot.h
parent52addcf9d6669fa439387610bc65c92fa0980cef (diff)
kernel: add support for kernel restart handler call chain
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 multiple 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. Introduce a system restart handler call chain to solve the described problems. This call chain is expected to be executed 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 call chain. By using the priority field in the notifier block, callers can control restart handler execution sequence and thus ensure that the restart handler with the optimal restart capabilities for a given system is called first. Signed-off-by: Guenter Roeck <linux@roeck-us.net> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Acked-by: Heiko Stuebner <heiko@sntech.de> Cc: Russell King <linux@arm.linux.org.uk> Cc: Wim Van Sebroeck <wim@iguana.be> Cc: Maxime Ripard <maxime.ripard@free-electrons.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Jonas Jensen <jonas.jensen@gmail.com> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Tomasz Figa <t.figa@samsung.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'include/linux/reboot.h')
-rw-r--r--include/linux/reboot.h3
1 files changed, 3 insertions, 0 deletions
diff --git a/include/linux/reboot.h b/include/linux/reboot.h
index 48bf152761c7..67fc8fcdc4b0 100644
--- a/include/linux/reboot.h
+++ b/include/linux/reboot.h
@@ -38,6 +38,9 @@ extern int reboot_force;
extern int register_reboot_notifier(struct notifier_block *);
extern int unregister_reboot_notifier(struct notifier_block *);
+extern int register_restart_handler(struct notifier_block *);
+extern int unregister_restart_handler(struct notifier_block *);
+extern void do_kernel_restart(char *cmd);
/*
* Architecture-specific implementations of sys_reboot commands.