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>

1 files changed, 4 insertions, 9 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;
 }