diff options
| author | Dave Martin <dave.martin@linaro.org> | 2011-02-09 12:06:59 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2011-02-10 15:30:51 +0000 |
| commit | 917692f5f7ec63de3b093c825913d68e910db282 (patch) | |
| tree | d4f2a59ca417c446450df0c1a84384fcef501c7f /arch/arm | |
| parent | 774c096bf9e49eebf7b5d2d9fdddf632c29ccea0 (diff) | |
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 <dave.martin@linaro.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm')
| -rw-r--r-- | arch/arm/include/asm/spinlock.h | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/arch/arm/include/asm/spinlock.h b/arch/arm/include/asm/spinlock.h index da1af524015..fdd3820edff 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") |