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efi: Don't use spinlocks for efi vars

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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>
This commit is contained in:
Sylvain Chouleur 2016-07-15 21:36:30 +02:00 • committed by Matt Fleming
parent 217b27d467
commit 21b3ddd39f
6 changed files with 139 additions and 76 deletions
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6
include/linux/efi.h
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@ -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 *),