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author | Vitaly Kuznetsov <vkuznets@redhat.com> | 2015-08-05 10:52:46 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-08-05 21:46:44 +0300 |
commit | 89af7ba5740b5937d10c8de93e79e71e5a933041 (patch) | |
tree | 0717f4e10938962d7fb57683d1efc8236e9956fd | |
parent | 54bf725e5d21022b25fe0d3c103fe82ed13b870b (diff) | |
download | linux-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>
-rw-r--r-- | Documentation/power/suspend-and-cpuhotplug.txt | 6 | ||||
-rw-r--r-- | kernel/cpu.c | 21 |
2 files changed, 16 insertions, 11 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 | | diff --git a/kernel/cpu.c b/kernel/cpu.c index 5644ec5582b9..0fca2ba96138 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -191,14 +191,14 @@ void cpu_hotplug_done(void) void cpu_hotplug_disable(void) { cpu_maps_update_begin(); - cpu_hotplug_disabled = 1; + cpu_hotplug_disabled++; cpu_maps_update_done(); } void cpu_hotplug_enable(void) { cpu_maps_update_begin(); - cpu_hotplug_disabled = 0; + WARN_ON(--cpu_hotplug_disabled < 0); cpu_maps_update_done(); } @@ -608,13 +608,18 @@ int disable_nonboot_cpus(void) } } - if (!error) { + if (!error) BUG_ON(num_online_cpus() > 1); - /* Make sure the CPUs won't be enabled by someone else */ - cpu_hotplug_disabled = 1; - } else { + else pr_err("Non-boot CPUs are not disabled\n"); - } + + /* + * Make sure the CPUs won't be enabled by someone else. We need to do + * this even in case of failure as all disable_nonboot_cpus() users are + * supposed to do enable_nonboot_cpus() on the failure path. + */ + cpu_hotplug_disabled++; + cpu_maps_update_done(); return error; } @@ -633,7 +638,7 @@ void __ref enable_nonboot_cpus(void) /* Allow everyone to use the CPU hotplug again */ cpu_maps_update_begin(); - cpu_hotplug_disabled = 0; + WARN_ON(--cpu_hotplug_disabled < 0); if (cpumask_empty(frozen_cpus)) goto out; |