Re: [PATCH 3/4] xen/manage: Guard against user-space initiated poweroff and XenBus.

From: David Vrabel
Date: Tue Apr 01 2014 - 09:18:17 EST

On 08/11/13 17:38, Konrad Rzeszutek Wilk wrote:
> There is a race case where the user does 'poweroff'
> and at the same time the system admin does 'xl shutdown'.
> Depending on the race, the system_state will be SYSTEM_RUNNING or
> SYSTEM_POWER_OFF. If SYSTEM_RUNNING we just end up making
> a duplicate call to 'poweroff' (while it is running).
> That will fail or execute (And if executed then it will be
> stuck in the reboot_mutex mutex). But nobody will care b/c the
> machine is in poweroff sequence.

If this race isn't a problem...

> If the system_state is SYSTEM_POWER_OFF then we end up making
> a duplicate call to kernel_power_off. There is no locking
> there so we walk in the same steps as what 'poweroff'
> has been doing.

... and this one doesn't happen because do_power_off() calls
orderly_poweroff(false) so does not call kernel_power_off().

Then isn't the patch unnecessary?

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