From 89af7ba5740b5937d10c8de93e79e71e5a933041 Mon Sep 17 00:00:00 2001 From: Vitaly Kuznetsov Date: Wed, 5 Aug 2015 00:52:46 -0700 Subject: 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 Reviewed-by: Thomas Gleixner Signed-off-by: K. Y. Srinivasan Signed-off-by: Greg Kroah-Hartman --- kernel/cpu.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-) (limited to 'kernel/cpu.c') 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; -- cgit v1.2.3-58-ga151