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authorVitaly Kuznetsov <vkuznets@redhat.com>2015-08-05 10:52:46 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-08-05 21:46:44 +0300
commit89af7ba5740b5937d10c8de93e79e71e5a933041 (patch)
tree0717f4e10938962d7fb57683d1efc8236e9956fd /Documentation/power
parent54bf725e5d21022b25fe0d3c103fe82ed13b870b (diff)
downloadlinux-89af7ba5740b5937d10c8de93e79e71e5a933041.tar.xz
cpu-hotplug: convert cpu_hotplug_disabled to a counter
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 <vkuznets@redhat.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation/power')
-rw-r--r--Documentation/power/suspend-and-cpuhotplug.txt6
1 files changed, 3 insertions, 3 deletions
diff --git a/Documentation/power/suspend-and-cpuhotplug.txt b/Documentation/power/suspend-and-cpuhotplug.txt
index 2850df3bf957..2fc909502db5 100644
--- a/Documentation/power/suspend-and-cpuhotplug.txt
+++ b/Documentation/power/suspend-and-cpuhotplug.txt
@@ -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
|
|