[PATCH v2 01/52] CPU hotplug: Add lockdep annotations to get/put_online_cpus()

[Srivatsa S. Bhat]

From: Gautham R. Shenoy <e...@linux.vnet.ibm.com>

Add lockdep annotations for get/put_online_cpus() and
cpu_hotplug_begin()/cpu_hotplug_end().

Cc: Ingo Molnar <mi...@kernel.org>
Reviewed-by: Oleg Nesterov <o...@redhat.com>
Signed-off-by: Gautham R. Shenoy <e...@linux.vnet.ibm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.b...@linux.vnet.ibm.com>
---

 kernel/cpu.c |   17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/kernel/cpu.c b/kernel/cpu.c
index deff2e6..33caf5e 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -19,6 +19,7 @@
 #include <linux/mutex.h>
 #include <linux/gfp.h>
 #include <linux/suspend.h>
+#include <linux/lockdep.h>
 
 #include "smpboot.h"
 
@@ -57,17 +58,30 @@ static struct {
         * an ongoing cpu hotplug operation.
         */
        int refcount;
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+       struct lockdep_map dep_map;
+#endif
 } cpu_hotplug = {
        .active_writer = NULL,
        .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
        .refcount = 0,
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+       .dep_map = {.name = "cpu_hotplug.lock" },
+#endif
 };
 
+/* Lockdep annotations for get/put_online_cpus() and cpu_hotplug_begin/end() */
+#define cpuhp_lock_acquire_read() lock_map_acquire_read(&cpu_hotplug.dep_map)
+#define cpuhp_lock_acquire()      lock_map_acquire(&cpu_hotplug.dep_map)
+#define cpuhp_lock_release()      lock_map_release(&cpu_hotplug.dep_map)
+
 void get_online_cpus(void)
 {
        might_sleep();
        if (cpu_hotplug.active_writer == current)
                return;
+       cpuhp_lock_acquire_read();
        mutex_lock(&cpu_hotplug.lock);
        cpu_hotplug.refcount++;
        mutex_unlock(&cpu_hotplug.lock);
@@ -87,6 +101,7 @@ void put_online_cpus(void)
        if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer))
                wake_up_process(cpu_hotplug.active_writer);
        mutex_unlock(&cpu_hotplug.lock);
+       cpuhp_lock_release();
 
 }
 EXPORT_SYMBOL_GPL(put_online_cpus);
@@ -117,6 +132,7 @@ void cpu_hotplug_begin(void)
 {
        cpu_hotplug.active_writer = current;
 
+       cpuhp_lock_acquire();
        for (;;) {
                mutex_lock(&cpu_hotplug.lock);
                if (likely(!cpu_hotplug.refcount))
@@ -131,6 +147,7 @@ void cpu_hotplug_done(void)
 {
        cpu_hotplug.active_writer = NULL;
        mutex_unlock(&cpu_hotplug.lock);
+       cpuhp_lock_release();
 }
 
 /*

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