Commit 6e30a7c9 authored by Uros Bizjak's avatar Uros Bizjak Committed by Ingo Molnar
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locking/atomic/x86: Introduce the read64_nonatomic macro to x86_32 with cx8 



As described in commit:

  e73c4e34 ("locking/atomic/x86: Introduce arch_atomic64_read_nonatomic() to x86_32")

the value preload before the CMPXCHG loop does not need to be atomic.

Introduce the read64_nonatomic assembly macro to load the value from a
atomic_t location in a faster non-atomic way and use it in
atomic64_cx8_32.S.

Signed-off-by: default avatarUros Bizjak <ubizjak@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20240605181424.3228-1-ubizjak@gmail.com
parent 51835949

arch/x86/lib/atomic64_cx8_32.S

+7 −2
Original line number Diff line number Diff line
@@ -16,6 +16,11 @@ 
	cmpxchg8b (\reg)

.endm



.macro read64_nonatomic reg

	movl (\reg), %eax

	movl 4(\reg), %edx

.endm



SYM_FUNC_START(atomic64_read_cx8)

	read64 %ecx

	RET
@@ -51,7 +56,7 @@ SYM_FUNC_START(atomic64_\func\()_return_cx8) 
	movl %edx, %edi

	movl %ecx, %ebp



	read64 %ecx

	read64_nonatomic %ecx

1:

	movl %eax, %ebx

	movl %edx, %ecx
@@ -79,7 +84,7 @@ addsub_return sub sub sbb 
SYM_FUNC_START(atomic64_\func\()_return_cx8)

	pushl %ebx



	read64 %esi

	read64_nonatomic %esi

1:

	movl %eax, %ebx

	movl %edx, %ecx