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SubjectRe: [PATCH] MIPS: Enable interrupts before WAIT instruction.


On Thu, 2 May 2013, David Daney wrote:

> From: David Daney <david.daney@cavium.com>
>
> As noted by Thomas Gleixner:
>
> commit cdbedc61c8 (mips: Use generic idle loop) broke MIPS as I did
> not realize that MIPS wants to invoke the wait instructions with
> interrupts enabled.
>
> Instead of enabling interrupts in arch_cpu_idle() as Thomas' initial
> patch does, we follow Linus' suggestion of doing it in the assembly
> code to prevent the compiler from rearranging things.

Yeah, that looks way more sane.


> Signed-off-by: David Daney <david.daney@cavium.com>
> Reported-by: EunBong Song <eunb.song@samsung.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Jonas Gorski <jogo@openwrt.org>
> ---
>
> This is only very lightly tested, we need more testing before
> declaring it the definitive fix.
>
> arch/mips/kernel/genex.S | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/arch/mips/kernel/genex.S b/arch/mips/kernel/genex.S
> index ecb347c..57cda9a 100644
> --- a/arch/mips/kernel/genex.S
> +++ b/arch/mips/kernel/genex.S
> @@ -132,12 +132,13 @@ LEAF(r4k_wait)
> .set noreorder
> /* start of rollback region */
> LONG_L t0, TI_FLAGS($28)
> - nop
> andi t0, _TIF_NEED_RESCHED
> bnez t0, 1f
> nop
> - nop
> - nop
> + /* Enable interrupts so WAIT will complete */
> + mfc0 t0, CP0_STATUS
> + ori t0, ST0_IE
> + mtc0 t0, CP0_STATUS
> .set mips3
> wait
> /* end of rollback region (the region size must be power of two) */
> --
> 1.7.11.7
>
>


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