summaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
authorToshi Kani <toshi.kani@hp.com>2013-08-12 09:45:53 -0600
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2013-08-13 12:20:16 +0200
commitb9d10be7a8e88fdcb12540387c219cdde87b0795 (patch)
treeac6c78fb28efccbba5995eb55b3b151096dfff19
parent22e7551eb6fd58352930306039a98313c011e615 (diff)
downloadlinux-b9d10be7a8e88fdcb12540387c219cdde87b0795.tar.bz2
ACPI / processor: Acquire writer lock to update CPU maps
CPU system maps are protected with reader/writer locks. The reader lock, get_online_cpus(), assures that the maps are not updated while holding the lock. The writer lock, cpu_hotplug_begin(), is used to udpate the cpu maps along with cpu_maps_update_begin(). However, the ACPI processor handler updates the cpu maps without holding the the writer lock. acpi_map_lsapic() is called from acpi_processor_hotadd_init() to update cpu_possible_mask and cpu_present_mask. acpi_unmap_lsapic() is called from acpi_processor_remove() to update cpu_possible_mask. Currently, they are either unprotected or protected with the reader lock, which is not correct. For example, the get_online_cpus() below is supposed to assure that cpu_possible_mask is not changed while the code is iterating with for_each_possible_cpu(). get_online_cpus(); for_each_possible_cpu(cpu) { : } put_online_cpus(); However, this lock has no protection with CPU hotplug since the ACPI processor handler does not use the writer lock when it updates cpu_possible_mask. The reader lock does not serialize within the readers. This patch protects them with the writer lock with cpu_hotplug_begin() along with cpu_maps_update_begin(), which must be held before calling cpu_hotplug_begin(). It also protects arch_register_cpu() / arch_unregister_cpu(), which creates / deletes a sysfs cpu device interface. For this purpose it changes cpu_hotplug_begin() and cpu_hotplug_done() to global and exports them in cpu.h. Signed-off-by: Toshi Kani <toshi.kani@hp.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
-rw-r--r--drivers/acpi/acpi_processor.c21
-rw-r--r--include/linux/cpu.h4
-rw-r--r--kernel/cpu.c9
3 files changed, 23 insertions, 11 deletions
diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
index 5a74a9c1e42c..f29e06efa479 100644
--- a/drivers/acpi/acpi_processor.c
+++ b/drivers/acpi/acpi_processor.c
@@ -178,14 +178,17 @@ static int acpi_processor_hotadd_init(struct acpi_processor *pr)
if (ACPI_FAILURE(status) || !(sta & ACPI_STA_DEVICE_PRESENT))
return -ENODEV;
+ cpu_maps_update_begin();
+ cpu_hotplug_begin();
+
ret = acpi_map_lsapic(pr->handle, &pr->id);
if (ret)
- return ret;
+ goto out;
ret = arch_register_cpu(pr->id);
if (ret) {
acpi_unmap_lsapic(pr->id);
- return ret;
+ goto out;
}
/*
@@ -195,7 +198,11 @@ static int acpi_processor_hotadd_init(struct acpi_processor *pr)
*/
pr_info("CPU%d has been hot-added\n", pr->id);
pr->flags.need_hotplug_init = 1;
- return 0;
+
+out:
+ cpu_hotplug_done();
+ cpu_maps_update_done();
+ return ret;
}
#else
static inline int acpi_processor_hotadd_init(struct acpi_processor *pr)
@@ -452,11 +459,15 @@ static void acpi_processor_remove(struct acpi_device *device)
per_cpu(processor_device_array, pr->id) = NULL;
per_cpu(processors, pr->id) = NULL;
+ cpu_maps_update_begin();
+ cpu_hotplug_begin();
+
/* Remove the CPU. */
- get_online_cpus();
arch_unregister_cpu(pr->id);
acpi_unmap_lsapic(pr->id);
- put_online_cpus();
+
+ cpu_hotplug_done();
+ cpu_maps_update_done();
try_offline_node(cpu_to_node(pr->id));
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index ab0eade73039..956c0a16566f 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -172,6 +172,8 @@ extern struct bus_type cpu_subsys;
#ifdef CONFIG_HOTPLUG_CPU
/* Stop CPUs going up and down. */
+extern void cpu_hotplug_begin(void);
+extern void cpu_hotplug_done(void);
extern void get_online_cpus(void);
extern void put_online_cpus(void);
extern void cpu_hotplug_disable(void);
@@ -197,6 +199,8 @@ static inline void cpu_hotplug_driver_unlock(void)
#else /* CONFIG_HOTPLUG_CPU */
+static inline void cpu_hotplug_begin(void) {}
+static inline void cpu_hotplug_done(void) {}
#define get_online_cpus() do { } while (0)
#define put_online_cpus() do { } while (0)
#define cpu_hotplug_disable() do { } while (0)
diff --git a/kernel/cpu.c b/kernel/cpu.c
index b2b227b82123..d7f07a2da5a6 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -113,7 +113,7 @@ EXPORT_SYMBOL_GPL(put_online_cpus);
* get_online_cpus() not an api which is called all that often.
*
*/
-static void cpu_hotplug_begin(void)
+void cpu_hotplug_begin(void)
{
cpu_hotplug.active_writer = current;
@@ -127,7 +127,7 @@ static void cpu_hotplug_begin(void)
}
}
-static void cpu_hotplug_done(void)
+void cpu_hotplug_done(void)
{
cpu_hotplug.active_writer = NULL;
mutex_unlock(&cpu_hotplug.lock);
@@ -154,10 +154,7 @@ void cpu_hotplug_enable(void)
cpu_maps_update_done();
}
-#else /* #if CONFIG_HOTPLUG_CPU */
-static void cpu_hotplug_begin(void) {}
-static void cpu_hotplug_done(void) {}
-#endif /* #else #if CONFIG_HOTPLUG_CPU */
+#endif /* CONFIG_HOTPLUG_CPU */
/* Need to know about CPUs going up/down? */
int __ref register_cpu_notifier(struct notifier_block *nb)