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Commit 917692f5 authored by Dave Martin's avatar Dave Martin Committed by Russell King
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ARM: 6655/1: Correct WFE() in asm/spinlock.h for Thumb-2 



The content for ALT_SMP() in the definition of WFE() expands to 6
bytes (IT cc ; WFEcc.W), which breaks the assumptions of the fixup
code, leading to lockups when the affected code gets run.

This patch works around the problem by explicitly using an
IT + WFEcc.N pair.

Signed-off-by: default avatarDave Martin <dave.martin@linaro.org>
Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 774c096b

arch/arm/include/asm/spinlock.h

+17 −1
Original line number Diff line number Diff line
@@ -18,7 +18,23 @@ 


#ifdef CONFIG_THUMB2_KERNEL

#define SEV		ALT_SMP("sev.w", "nop.w")

#define WFE(cond)	ALT_SMP("wfe" cond ".w", "nop.w")

/*

 * For Thumb-2, special care is needed to ensure that the conditional WFE

 * instruction really does assemble to exactly 4 bytes (as required by

 * the SMP_ON_UP fixup code).   By itself "wfene" might cause the

 * assembler to insert a extra (16-bit) IT instruction, depending on the

 * presence or absence of neighbouring conditional instructions.

 *

 * To avoid this unpredictableness, an approprite IT is inserted explicitly:

 * the assembler won't change IT instructions which are explicitly present

 * in the input.

 */

#define WFE(cond)	ALT_SMP(		\

	"it " cond "\n\t"			\

	"wfe" cond ".n",			\

						\

	"nop.w"					\

)

#else

#define SEV		ALT_SMP("sev", "nop")

#define WFE(cond)	ALT_SMP("wfe" cond, "nop")