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cpu-hotplug: convert cpu_hotplug_disabled to a counter

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As a prerequisite to exporting cpu_hotplug_enable/cpu_hotplug_disable
functions to modules we need to convert cpu_hotplug_disabled to a counter
to properly support disable -> disable -> enable call sequences. E.g.
after Hyper-V vmbus module (which is supposed to be the first user of
exported cpu_hotplug_enable/cpu_hotplug_disable) did cpu_hotplug_disable()
hibernate path calls disable_nonboot_cpus() and if we hit an error in
_cpu_down() enable_nonboot_cpus() will be called on the failure path (thus
making cpu_hotplug_disabled = 0 and leaving cpu hotplug in 'enabled'
state). Same problem is possible if more than 1 module use
cpu_hotplug_disable/cpu_hotplug_enable on their load/unload paths. When
one of these modules is been unloaded it is logical to leave cpu hotplug
in 'disabled' state.

To support the change we need to increse cpu_hotplug_disabled counter
in disable_nonboot_cpus() unconditionally as all users of
disable_nonboot_cpus() are supposed to do enable_nonboot_cpus() in case
an error was returned.

Signed-off-by: Vitaly Kuznetsov <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Signed-off-by: K. Y. Srinivasan <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
This commit is contained in:
Vitaly Kuznetsov 2015-08-05 00:52:46 -07:00 • committed by Greg Kroah-Hartman
commit 89af7ba574
2 changed files with 16 additions and 11 deletions
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6
Documentation/power/suspend-and-cpuhotplug.txt
View file

@ -72,7 +72,7 @@ More details follow:
|
v
Disable regular cpu hotplug
by setting cpu_hotplug_disabled=1
by increasing cpu_hotplug_disabled
|
v
Release cpu_add_remove_lock
@ -89,7 +89,7 @@ Resuming back is likewise, with the counterparts being (in the order of
execution during resume):
* enable_nonboot_cpus() which involves:
| Acquire cpu_add_remove_lock
| Reset cpu_hotplug_disabled to 0, thereby enabling regular cpu hotplug
| Decrease cpu_hotplug_disabled, thereby enabling regular cpu hotplug
| Call _cpu_up() [for all those cpus in the frozen_cpus mask, in a loop]
| Release cpu_add_remove_lock
v
@ -120,7 +120,7 @@ after the entire cycle is complete (i.e., suspend + resume).
Acquire cpu_add_remove_lock
|
v
If cpu_hotplug_disabled is 1
If cpu_hotplug_disabled > 0
return gracefully
|
|