| Message ID | 1444791077-26020-1-git-send-email-shengjiu.wang@freescale.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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.wang@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.
On Thu, Oct 15, 2015 at 09:24:17AM +0100, Russell King - ARM Linux wrote: > 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.wang@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. I am ok with your change. Need I send another patch for this change? or will you send it by yourself? best regards wang shengjiu > > -- > FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up > according to speedtest.net.
On Thu, Oct 15, 2015 at 04:36:31PM +0800, Shengjiu Wang wrote: > On Thu, Oct 15, 2015 at 09:24:17AM +0100, Russell King - ARM Linux wrote: > > 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.wang@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. > > I am ok with your change. Need I send another patch for this change? or will > you send it by yourself? Please send a new patch, thanks.
On 15/10/15 09:57, Russell King - ARM Linux wrote: > On Thu, Oct 15, 2015 at 04:36:31PM +0800, Shengjiu Wang wrote: >> On Thu, Oct 15, 2015 at 09:24:17AM +0100, Russell King - ARM Linux wrote: >>> 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.wang@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. >> >> I am ok with your change. Need I send another patch for this change? or will >> you send it by yourself? > > Please send a new patch, thanks. > We might need the same change for arm64 counterpart (see arch/arm64/kernel/armv8_deprecated.c). Vladimir
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" \
__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.wang@freescale.com> --- arch/arm/kernel/swp_emulate.c | 1 + 1 file changed, 1 insertion(+)