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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>
83 lines
1.9 KiB
C
83 lines
1.9 KiB
C
#ifndef _LINUX_REBOOT_H
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#define _LINUX_REBOOT_H
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#include <linux/notifier.h>
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#include <uapi/linux/reboot.h>
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#define SYS_DOWN 0x0001 /* Notify of system down */
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#define SYS_RESTART SYS_DOWN
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#define SYS_HALT 0x0002 /* Notify of system halt */
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#define SYS_POWER_OFF 0x0003 /* Notify of system power off */
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enum reboot_mode {
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REBOOT_COLD = 0,
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REBOOT_WARM,
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REBOOT_HARD,
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REBOOT_SOFT,
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REBOOT_GPIO,
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};
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extern enum reboot_mode reboot_mode;
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enum reboot_type {
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BOOT_TRIPLE = 't',
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BOOT_KBD = 'k',
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BOOT_BIOS = 'b',
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BOOT_ACPI = 'a',
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BOOT_EFI = 'e',
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BOOT_CF9_FORCE = 'p',
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BOOT_CF9_SAFE = 'q',
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};
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extern enum reboot_type reboot_type;
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extern int reboot_default;
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extern int reboot_cpu;
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extern int reboot_force;
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extern int register_reboot_notifier(struct notifier_block *);
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extern int unregister_reboot_notifier(struct notifier_block *);
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extern int register_restart_handler(struct notifier_block *);
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extern int unregister_restart_handler(struct notifier_block *);
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extern void do_kernel_restart(char *cmd);
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/*
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* Architecture-specific implementations of sys_reboot commands.
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*/
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extern void migrate_to_reboot_cpu(void);
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extern void machine_restart(char *cmd);
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extern void machine_halt(void);
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extern void machine_power_off(void);
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extern void machine_shutdown(void);
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struct pt_regs;
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extern void machine_crash_shutdown(struct pt_regs *);
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/*
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* Architecture independent implemenations of sys_reboot commands.
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*/
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extern void kernel_restart_prepare(char *cmd);
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extern void kernel_restart(char *cmd);
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extern void kernel_halt(void);
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extern void kernel_power_off(void);
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extern int C_A_D; /* for sysctl */
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void ctrl_alt_del(void);
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#define POWEROFF_CMD_PATH_LEN 256
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extern char poweroff_cmd[POWEROFF_CMD_PATH_LEN];
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extern int orderly_poweroff(bool force);
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/*
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* Emergency restart, callable from an interrupt handler.
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*/
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extern void emergency_restart(void);
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#include <asm/emergency-restart.h>
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#endif /* _LINUX_REBOOT_H */
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