On Wed, Oct 14, 2015 at 10:51:17AM +0800, Shengjiu Wang wrote:
> __user_swpX_asm maybe failed in first STREX operation, emulate_swpX
> will try again, but the *data has been changed in first time. which
> cause the result is wrong. So need to recover the *data when failed.
>
> Signed-off-by: Shengjiu Wang <shengjiu.w...@freescale.com>
> ---
> arch/arm/kernel/swp_emulate.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/arm/kernel/swp_emulate.c b/arch/arm/kernel/swp_emulate.c
> index 5b26e7e..c61fbf92 100644
> --- a/arch/arm/kernel/swp_emulate.c
> +++ b/arch/arm/kernel/swp_emulate.c
> @@ -41,6 +41,7 @@
> "1: strex"B" %0, %2, [%3]\n" \
> " cmp %0, #0\n" \
> " movne %0, %4\n" \
> + " movne %1, %2\n" \
> "2:\n" \
> " .section .text.fixup,\"ax\"\n" \
> " .align 2\n" \
I think I'd prefer this to be:
__asm__ __volatile__( \
"0: ldrex"B" %2, [%3]\n" \
"1: strex"B" %0, %1, [%3]\n" \
" cmp %0, #0\n" \
" moveq %1, %2\n" \
" movne %0, %4\n" \
so that we're not loading into %1 (an in-out non-temporary) but rather
loading it into a temporary - and only overwriting the saved register
value if the swap succeeds.
Thanks.
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