The arch_local_irq_save(), etc., routines are required to function as compiler barriers. They do, but it's subtle and requires knowing that the gcc builtin __insn_mtspr() is marked as a memory clobber. Provide a comment explaining the assumption. Signed-off-by: Chris Metcalf <cmetcalf@xxxxxxxxxx> --- arch/tile/include/asm/irqflags.h | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) Linus wrote: > Some other architectures (tile) have such subtle implementations > (where is __insn_mtspr() defined?) that I have a hard time judging. diff --git a/arch/tile/include/asm/irqflags.h b/arch/tile/include/asm/irqflags.h index 241c0bb..c96f9bb 100644 --- a/arch/tile/include/asm/irqflags.h +++ b/arch/tile/include/asm/irqflags.h @@ -40,7 +40,15 @@ #include <asm/percpu.h> #include <arch/spr_def.h> -/* Set and clear kernel interrupt masks. */ +/* + * Set and clear kernel interrupt masks. + * + * NOTE: __insn_mtspr() is a compiler builtin marked as a memory + * clobber. We rely on it being equivalent to a compiler barrier in + * this code since arch_local_irq_save() and friends must act as + * compiler barriers. This compiler semantic is baked into enough + * places that the compiler will maintain it going forward. + */ #if CHIP_HAS_SPLIT_INTR_MASK() #if INT_PERF_COUNT < 32 || INT_AUX_PERF_COUNT < 32 || INT_MEM_ERROR >= 32 # error Fix assumptions about which word various interrupts are in -- 1.7.10.3 -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
