From 917692f5f7ec63de3b093c825913d68e910db282 Mon Sep 17 00:00:00 2001 From: Dave Martin Date: Wed, 9 Feb 2011 12:06:59 +0100 Subject: 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: Dave Martin Acked-by: Will Deacon Signed-off-by: Russell King diff --git a/arch/arm/include/asm/spinlock.h b/arch/arm/include/asm/spinlock.h index da1af52..fdd3820 100644 --- a/arch/arm/include/asm/spinlock.h +++ b/arch/arm/include/asm/spinlock.h @@ -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") -- cgit v0.10.2