On 02/12/2014 05:19 AM, Andrew Morton wrote:
There are three locks involved in two sequence:
a) pm suspend:
console_lock (@suspend_console())
cpu_add_remove_lock (@disable_nonboot_cpus())
cpu_hotplug.lock (@_cpu_down())
But but but. suspend_console() releases console_sem again.
Console_lock does not refer to console_sem but console_lock_dep_map. Its name
is console_lock. Suspend_console() does not release console_lock_dep_map.
So the
sequence is actually
down(&console_sem) (@suspend_console())
acquire(&console_lock_dep_map) (&suspend_console())
up(&console_sem) (@suspend_console())
cpu_add_remove_lock (@disable_nonboot_cpus())
cpu_hotplug.lock (@_cpu_down())
So console_sem *doesn't* nest outside cpu_add_remove_lock and
cpu_hotplug.lock.
Add console_lock in the sequence.
b) Plug-out CPUx:
cpu_add_remove_lock (@(cpu_down())
cpu_hotplug.lock (@_cpu_down())
console_lock (@console_cpu_notify()) => Lockdeps prints warning log.
There should be not real deadlock, as flag of console_suspended can
protect this.
console_lock() does down(&console_sem) *before* testing
console_suspended, so I don't understand this sentence - a more
detailed description would help.
After suspend_console(), console_sem is unlocked, but console_lock_dep_map has
been acquired.
Best Regards,
Jane
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