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efi: Replace runtime services spinlock with semaphore

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The purpose of the efi_runtime_lock is to prevent concurrent calls into
the firmware. There is no need to use spinlocks here, as long as we ensure
that runtime service invocations from an atomic context (i.e., EFI pstore)
cannot block.

So use a semaphore instead, and use down_trylock() in the nonblocking case.
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: 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:
Ard Biesheuvel
2016-07-15 21:36:31 +02:00
committed by Matt Fleming
parent 21b3ddd39f
commit dce48e351c
3 changed files with 53 additions and 32 deletions
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include/linux/efi.h
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@@ -38,6 +38,7 @@
#define EFI_WRITE_PROTECTED ( 8 | (1UL << (BITS_PER_LONG-1)))
#define EFI_OUT_OF_RESOURCES ( 9 | (1UL << (BITS_PER_LONG-1)))
#define EFI_NOT_FOUND (14 | (1UL << (BITS_PER_LONG-1)))
#define EFI_ABORTED (21 | (1UL << (BITS_PER_LONG-1)))
#define EFI_SECURITY_VIOLATION (26 | (1UL << (BITS_PER_LONG-1)))
typedef unsigned long efi_status_t;