efi: Don't use spinlocks for efi vars

All efivars operations are protected by a spinlock which prevents
interruptions and preemption. This is too restricted, we just need a
lock preventing concurrency.
The idea is to use a semaphore of count 1 and to have two ways of
locking, depending on the context:
- In interrupt context, we call down_trylock(), if it fails we return
  an error
- In normal context, we call down_interruptible()

We don't use a mutex here because the mutex_trylock() function must not
be called from interrupt context, whereas the down_trylock() can.

Signed-off-by: Sylvain Chouleur <sylvain.chouleur@intel.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Sylvain Chouleur <sylvain.chouleur@gmail.com>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>

1 files changed, 3 insertions, 3 deletions

diff --git a/include/linux/efi.h b/include/linux/efi.h
index deecb2902715..4d6da7b66c19 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1297,8 +1297,8 @@ struct kobject *efivars_kobject(void);
 int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *),
 		void *data, bool duplicates, struct list_head *head);
 
-void efivar_entry_add(struct efivar_entry *entry, struct list_head *head);
-void efivar_entry_remove(struct efivar_entry *entry);
+int efivar_entry_add(struct efivar_entry *entry, struct list_head *head);
+int efivar_entry_remove(struct efivar_entry *entry);
 
 int __efivar_entry_delete(struct efivar_entry *entry);
 int efivar_entry_delete(struct efivar_entry *entry);
@@ -1315,7 +1315,7 @@ int efivar_entry_set_get_size(struct efivar_entry *entry, u32 attributes,
 int efivar_entry_set_safe(efi_char16_t *name, efi_guid_t vendor, u32 attributes,
 			  bool block, unsigned long size, void *data);
 
-void efivar_entry_iter_begin(void);
+int efivar_entry_iter_begin(void);
 void efivar_entry_iter_end(void);
 
 int __efivar_entry_iter(int (*func)(struct efivar_entry *, void *),