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kernel/reboot: explicitly notify if halt occurred instead of power off

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When kernel_can_power_off() returns false, and reboot has called with
LINUX_REBOOT_CMD_POWER_OFF, kernel_halt() will be initiated instead of
actual power off function.

However, in this situation, Kernel never explicitly notifies user that
system halted instead of requested power off.

Since halt and power off perform different behavior, and user initiated
reboot call with power off command, not halt, This could be unintended
behavior to user, like this:

~ # poweroff -f
[    3.581482] reboot: System halted

Therefore, this explicitly notifies user that poweroff is not available,
and halting has been occured as an alternative behavior instead:

~ # poweroff -f
[    4.123668] reboot: Power off not available: System halted instead

[akpm@linux-foundation.org: tweak comment text]
Link: https://lkml.kernel.org/r/20231104113320.72440-1-ldmldm05@gmail.com
Signed-off-by: Dongmin Lee <ldmldm05@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Dongmin Lee 2023-11-04 20:33:20 +09:00 committed by Andrew Morton
parent 0c92218f4e
commit a9a1d6ad66
1 changed files with 15 additions and 2 deletions
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17
kernel/reboot.c
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@ -58,6 +58,14 @@ struct sys_off_handler {
struct device *dev;
};
/*
* This variable is used to indicate if a halt was initiated instead of a
* reboot when the reboot call was invoked with LINUX_REBOOT_CMD_POWER_OFF, but
* the system cannot be powered off. This allowes kernel_halt() to notify users
* of that.
*/
static bool poweroff_fallback_to_halt;
/*
* Temporary stub that prevents linkage failure while we're in process
* of removing all uses of legacy pm_power_off() around the kernel.
@ -297,7 +305,10 @@ void kernel_halt(void)
kernel_shutdown_prepare(SYSTEM_HALT);
migrate_to_reboot_cpu();
syscore_shutdown();
pr_emerg("System halted\n");
if (poweroff_fallback_to_halt)
pr_emerg("Power off not available: System halted instead\n");
else
pr_emerg("System halted\n");
kmsg_dump(KMSG_DUMP_SHUTDOWN);
machine_halt();
}
@ -732,8 +743,10 @@ SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
/* Instead of trying to make the power_off code look like
* halt when pm_power_off is not set do it the easy way.
*/
if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !kernel_can_power_off())
if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !kernel_can_power_off()) {
poweroff_fallback_to_halt = true;
cmd = LINUX_REBOOT_CMD_HALT;
}
mutex_lock(&system_transition_mutex);
switch (cmd) {