ACPI: convert acpi_device_lock spinlock to mutex

Convert acpi_device_lock to a mutex to avoid
a potential race upon access to /proc/acpi/wakeup

Delete the lock entirely in wakeup.c
since it is not necessary (and can not sleep)

Found-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

4 files changed, 21 insertions, 39 deletions

diff --git a/drivers/acpi/proc.c b/drivers/acpi/proc.c
index 05dfdc96802e..d0d550d22a6d 100644
--- a/drivers/acpi/proc.c
+++ b/drivers/acpi/proc.c
@@ -343,9 +343,6 @@ acpi_system_write_alarm(struct file *file,
 }
 #endif                          /* HAVE_ACPI_LEGACY_ALARM */
 
-extern struct list_head acpi_wakeup_device_list;
-extern spinlock_t acpi_device_lock;
-
 static int
 acpi_system_wakeup_device_seq_show(struct seq_file *seq, void *offset)
 {
@@ -353,7 +350,7 @@ acpi_system_wakeup_device_seq_show(struct seq_file *seq, void *offset)
 
         seq_printf(seq, "Device\tS-state\t  Status   Sysfs node\n");
 
-        spin_lock(&acpi_device_lock);
+        mutex_lock(&acpi_device_lock);
         list_for_each_safe(node, next, &acpi_wakeup_device_list) {
                 struct acpi_device *dev =
                     container_of(node, struct acpi_device, wakeup_list);
@@ -361,7 +358,6 @@ acpi_system_wakeup_device_seq_show(struct seq_file *seq, void *offset)
 
                 if (!dev->wakeup.flags.valid)
                         continue;
-                spin_unlock(&acpi_device_lock);
 
                 ldev = acpi_get_physical_device(dev->handle);
                 seq_printf(seq, "%s\t  S%d\t%c%-8s  ",
@@ -376,9 +372,8 @@ acpi_system_wakeup_device_seq_show(struct seq_file *seq, void *offset)
                 seq_printf(seq, "\n");
                 put_device(ldev);
 
-                spin_lock(&acpi_device_lock);
         }
-        spin_unlock(&acpi_device_lock);
+        mutex_unlock(&acpi_device_lock);
         return 0;
 }
 
@@ -409,7 +404,7 @@ acpi_system_write_wakeup_device(struct file *file,
         strbuf[len] = '\0';
         sscanf(strbuf, "%s", str);
 
-        spin_lock(&acpi_device_lock);
+        mutex_lock(&acpi_device_lock);
         list_for_each_safe(node, next, &acpi_wakeup_device_list) {
                 struct acpi_device *dev =
                     container_of(node, struct acpi_device, wakeup_list);
@@ -446,7 +441,7 @@ acpi_system_write_wakeup_device(struct file *file,
                         }
                 }
         }
-        spin_unlock(&acpi_device_lock);
+        mutex_unlock(&acpi_device_lock);
         return count;
 }
 
diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 20c23c049207..e63f2febad84 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -24,7 +24,7 @@ extern struct acpi_device *acpi_root;
 
 static LIST_HEAD(acpi_device_list);
 static LIST_HEAD(acpi_bus_id_list);
-DEFINE_SPINLOCK(acpi_device_lock);
+DEFINE_MUTEX(acpi_device_lock);
 LIST_HEAD(acpi_wakeup_device_list);
 
 struct acpi_device_bus_id{
@@ -500,7 +500,7 @@ static int acpi_device_register(struct acpi_device *device,
                 return -ENOMEM;
         }
 
-        spin_lock(&acpi_device_lock);
+        mutex_lock(&acpi_device_lock);
         /*
          * Find suitable bus_id and instance number in acpi_bus_id_list
          * If failed, create one and link it into acpi_bus_id_list
@@ -528,7 +528,7 @@ static int acpi_device_register(struct acpi_device *device,
                 list_add_tail(&device->g_list, &acpi_device_list);
         if (device->wakeup.flags.valid)
                 list_add_tail(&device->wakeup_list, &acpi_wakeup_device_list);
-        spin_unlock(&acpi_device_lock);
+        mutex_unlock(&acpi_device_lock);
 
         if (device->parent)
                 device->dev.parent = &parent->dev;
@@ -549,20 +549,20 @@ static int acpi_device_register(struct acpi_device *device,
         device->removal_type = ACPI_BUS_REMOVAL_NORMAL;
         return 0;
   end:
-        spin_lock(&acpi_device_lock);
+        mutex_lock(&acpi_device_lock);
         if (device->parent) {
                 list_del(&device->node);
                 list_del(&device->g_list);
         } else
                 list_del(&device->g_list);
         list_del(&device->wakeup_list);
-        spin_unlock(&acpi_device_lock);
+        mutex_unlock(&acpi_device_lock);
         return result;
 }
 
 static void acpi_device_unregister(struct acpi_device *device, int type)
 {
-        spin_lock(&acpi_device_lock);
+        mutex_lock(&acpi_device_lock);
         if (device->parent) {
                 list_del(&device->node);
                 list_del(&device->g_list);
@@ -570,7 +570,7 @@ static void acpi_device_unregister(struct acpi_device *device, int type)
                 list_del(&device->g_list);
 
         list_del(&device->wakeup_list);
-        spin_unlock(&acpi_device_lock);
+        mutex_unlock(&acpi_device_lock);
 
         acpi_detach_data(device->handle, acpi_bus_data_handler);
 
diff --git a/drivers/acpi/sleep.h b/drivers/acpi/sleep.h
index cfaf8f5b0a14..8a8f3b3382a6 100644
--- a/drivers/acpi/sleep.h
+++ b/drivers/acpi/sleep.h
@@ -5,3 +5,6 @@ extern int acpi_suspend (u32 state);
 extern void acpi_enable_wakeup_device_prep(u8 sleep_state);
 extern void acpi_enable_wakeup_device(u8 sleep_state);
 extern void acpi_disable_wakeup_device(u8 sleep_state);
+
+extern struct list_head acpi_wakeup_device_list;
+extern struct mutex acpi_device_lock;
diff --git a/drivers/acpi/wakeup.c b/drivers/acpi/wakeup.c
index 5aee8c26cc9f..88725dcdf8bc 100644
--- a/drivers/acpi/wakeup.c
+++ b/drivers/acpi/wakeup.c
@@ -12,12 +12,14 @@
 #include "internal.h"
 #include "sleep.h"
 
+/*
+ * We didn't lock acpi_device_lock in the file, because it invokes oops in
+ * suspend/resume and isn't really required as this is called in S-state. At
+ * that time, there is no device hotplug
+ **/
 #define _COMPONENT              ACPI_SYSTEM_COMPONENT
 ACPI_MODULE_NAME("wakeup_devices")
 
-extern struct list_head acpi_wakeup_device_list;
-extern spinlock_t acpi_device_lock;
-
 /**
  * acpi_enable_wakeup_device_prep - prepare wakeup devices
  *      @sleep_state:   ACPI state
@@ -29,7 +31,6 @@ void acpi_enable_wakeup_device_prep(u8 sleep_state)
 {
         struct list_head *node, *next;
 
-        spin_lock(&acpi_device_lock);
         list_for_each_safe(node, next, &acpi_wakeup_device_list) {
                 struct acpi_device *dev = container_of(node,
                                                        struct acpi_device,
@@ -40,11 +41,8 @@ void acpi_enable_wakeup_device_prep(u8 sleep_state)
                     (sleep_state > (u32) dev->wakeup.sleep_state))
                         continue;
 
-                spin_unlock(&acpi_device_lock);
                 acpi_enable_wakeup_device_power(dev, sleep_state);
-                spin_lock(&acpi_device_lock);
         }
-        spin_unlock(&acpi_device_lock);
 }
 
 /**
@@ -60,7 +58,6 @@ void acpi_enable_wakeup_device(u8 sleep_state)
          * Caution: this routine must be invoked when interrupt is disabled 
          * Refer ACPI2.0: P212
          */
-        spin_lock(&acpi_device_lock);
         list_for_each_safe(node, next, &acpi_wakeup_device_list) {
                 struct acpi_device *dev =
                         container_of(node, struct acpi_device, wakeup_list);
@@ -74,22 +71,17 @@ void acpi_enable_wakeup_device(u8 sleep_state)
                 if ((!dev->wakeup.state.enabled && !dev->wakeup.flags.prepared)
                     || sleep_state > (u32) dev->wakeup.sleep_state) {
                         if (dev->wakeup.flags.run_wake) {
-                                spin_unlock(&acpi_device_lock);
                                 /* set_gpe_type will disable GPE, leave it like that */
                                 acpi_set_gpe_type(dev->wakeup.gpe_device,
                                                   dev->wakeup.gpe_number,
                                                   ACPI_GPE_TYPE_RUNTIME);
-                                spin_lock(&acpi_device_lock);
                         }
                         continue;
                 }
-                spin_unlock(&acpi_device_lock);
                 if (!dev->wakeup.flags.run_wake)
                         acpi_enable_gpe(dev->wakeup.gpe_device,
                                         dev->wakeup.gpe_number);
-                spin_lock(&acpi_device_lock);
         }
-        spin_unlock(&acpi_device_lock);
 }
 
 /**
@@ -101,7 +93,6 @@ void acpi_disable_wakeup_device(u8 sleep_state)
 {
         struct list_head *node, *next;
 
-        spin_lock(&acpi_device_lock);
         list_for_each_safe(node, next, &acpi_wakeup_device_list) {
                 struct acpi_device *dev =
                         container_of(node, struct acpi_device, wakeup_list);
@@ -112,19 +103,16 @@ void acpi_disable_wakeup_device(u8 sleep_state)
                 if ((!dev->wakeup.state.enabled && !dev->wakeup.flags.prepared)
                     || sleep_state > (u32) dev->wakeup.sleep_state) {
                         if (dev->wakeup.flags.run_wake) {
-                                spin_unlock(&acpi_device_lock);
                                 acpi_set_gpe_type(dev->wakeup.gpe_device,
                                                   dev->wakeup.gpe_number,
                                                   ACPI_GPE_TYPE_WAKE_RUN);
                                 /* Re-enable it, since set_gpe_type will disable it */
                                 acpi_enable_gpe(dev->wakeup.gpe_device,
                                                 dev->wakeup.gpe_number);
-                                spin_lock(&acpi_device_lock);
                         }
                         continue;
                 }
 
-                spin_unlock(&acpi_device_lock);
                 acpi_disable_wakeup_device_power(dev);
                 /* Never disable run-wake GPE */
                 if (!dev->wakeup.flags.run_wake) {
@@ -133,16 +121,14 @@ void acpi_disable_wakeup_device(u8 sleep_state)
                         acpi_clear_gpe(dev->wakeup.gpe_device,
                                        dev->wakeup.gpe_number, ACPI_NOT_ISR);
                 }
-                spin_lock(&acpi_device_lock);
         }
-        spin_unlock(&acpi_device_lock);
 }
 
 int __init acpi_wakeup_device_init(void)
 {
         struct list_head *node, *next;
 
-        spin_lock(&acpi_device_lock);
+        mutex_lock(&acpi_device_lock);
         list_for_each_safe(node, next, &acpi_wakeup_device_list) {
                 struct acpi_device *dev = container_of(node,
                                                        struct acpi_device,
@@ -150,15 +136,13 @@ int __init acpi_wakeup_device_init(void)
                 /* In case user doesn't load button driver */
                 if (!dev->wakeup.flags.run_wake || dev->wakeup.state.enabled)
                         continue;
-                spin_unlock(&acpi_device_lock);
                 acpi_set_gpe_type(dev->wakeup.gpe_device,
                                   dev->wakeup.gpe_number,
                                   ACPI_GPE_TYPE_WAKE_RUN);
                 acpi_enable_gpe(dev->wakeup.gpe_device,
                                 dev->wakeup.gpe_number);
                 dev->wakeup.state.enabled = 1;
-                spin_lock(&acpi_device_lock);
         }
-        spin_unlock(&acpi_device_lock);
+        mutex_unlock(&acpi_device_lock);
         return 0;
 }