| Message ID | 20240805192119.56816-2-paulmck@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Provide emulation for one-byte cmpxchg() | expand |
Hi Paul, On 8/5/24 12:21, Paul E. McKenney wrote: > Use the new cmpxchg_emu_u8() to emulate one-byte cmpxchg() on arc. > > [ paulmck: Drop two-byte support per Arnd Bergmann feedback. ] > [ paulmck: Apply feedback from Naresh Kamboju. ] > [ paulmck: Apply kernel test robot feedback. ] > > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > Cc: Vineet Gupta <vgupta@kernel.org> > Cc: Andi Shyti <andi.shyti@linux.intel.com> > Cc: Andrzej Hajda <andrzej.hajda@intel.com> > Cc: Arnd Bergmann <arnd@arndb.de> > Cc: Palmer Dabbelt <palmer@rivosinc.com> > Cc: <linux-snps-arc@lists.infradead.org> > --- > arch/arc/Kconfig | 1 + > arch/arc/include/asm/cmpxchg.h | 33 ++++++++++++++++++++++++--------- > 2 files changed, 25 insertions(+), 9 deletions(-) > > diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig > index fd0b0a0d4686a..163608fd49d18 100644 > --- a/arch/arc/Kconfig > +++ b/arch/arc/Kconfig > @@ -13,6 +13,7 @@ config ARC > select ARCH_HAS_SETUP_DMA_OPS > select ARCH_HAS_SYNC_DMA_FOR_CPU > select ARCH_HAS_SYNC_DMA_FOR_DEVICE > + select ARCH_NEED_CMPXCHG_1_EMU > select ARCH_SUPPORTS_ATOMIC_RMW if ARC_HAS_LLSC > select ARCH_32BIT_OFF_T > select BUILDTIME_TABLE_SORT > diff --git a/arch/arc/include/asm/cmpxchg.h b/arch/arc/include/asm/cmpxchg.h > index e138fde067dea..2102ce076f28b 100644 > --- a/arch/arc/include/asm/cmpxchg.h > +++ b/arch/arc/include/asm/cmpxchg.h > @@ -8,6 +8,7 @@ > > #include <linux/build_bug.h> > #include <linux/types.h> > +#include <linux/cmpxchg-emu.h> > > #include <asm/barrier.h> > #include <asm/smp.h> > @@ -46,6 +47,9 @@ > __typeof__(*(ptr)) _prev_; \ > \ > switch(sizeof((_p_))) { \ > + case 1: \ > + _prev_ = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)_p_, (uintptr_t)_o_, (uintptr_t)_n_); \ > + break; \ > case 4: \ > _prev_ = __cmpxchg(_p_, _o_, _n_); \ > break; \ > @@ -65,16 +69,27 @@ > __typeof__(*(ptr)) _prev_; \ > unsigned long __flags; \ > \ > - BUILD_BUG_ON(sizeof(_p_) != 4); \ Is this alone not sufficient: i.e. for !LLSC let the atomic op happen under a spin-lock for non 4 byte quantities as well. > + switch(sizeof((_p_))) { \ > + case 1: \ > + __flags = cmpxchg_emu_u8((volatile u8 *)_p_, (uintptr_t)_o_, (uintptr_t)_n_); \ > + _prev_ = (__typeof__(*(ptr)))__flags; \ > + break; \ > + break; \ FWIW, the 2nd break seems extraneous. > + case 4: \ > + /* \ > + * spin lock/unlock provide the needed smp_mb() \ > + * before/after \ > + */ \ > + atomic_ops_lock(__flags); \ > + _prev_ = *_p_; \ > + if (_prev_ == _o_) \ > + *_p_ = _n_; \ > + atomic_ops_unlock(__flags); \ > + break; \ > + default: \ > + BUILD_BUG(); \ > + } \ > \ > - /* \ > - * spin lock/unlock provide the needed smp_mb() before/after \ > - */ \ > - atomic_ops_lock(__flags); \ > - _prev_ = *_p_; \ > - if (_prev_ == _o_) \ > - *_p_ = _n_; \ > - atomic_ops_unlock(__flags); \ > _prev_; \ > }) -Vineet
On Mon, Aug 05, 2024 at 06:27:57PM -0700, Vineet Gupta wrote: > Hi Paul, > > On 8/5/24 12:21, Paul E. McKenney wrote: > > Use the new cmpxchg_emu_u8() to emulate one-byte cmpxchg() on arc. > > > > [ paulmck: Drop two-byte support per Arnd Bergmann feedback. ] > > [ paulmck: Apply feedback from Naresh Kamboju. ] > > [ paulmck: Apply kernel test robot feedback. ] > > > > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > > Cc: Vineet Gupta <vgupta@kernel.org> > > Cc: Andi Shyti <andi.shyti@linux.intel.com> > > Cc: Andrzej Hajda <andrzej.hajda@intel.com> > > Cc: Arnd Bergmann <arnd@arndb.de> > > Cc: Palmer Dabbelt <palmer@rivosinc.com> > > Cc: <linux-snps-arc@lists.infradead.org> > > --- > > arch/arc/Kconfig | 1 + > > arch/arc/include/asm/cmpxchg.h | 33 ++++++++++++++++++++++++--------- > > 2 files changed, 25 insertions(+), 9 deletions(-) > > > > diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig > > index fd0b0a0d4686a..163608fd49d18 100644 > > --- a/arch/arc/Kconfig > > +++ b/arch/arc/Kconfig > > @@ -13,6 +13,7 @@ config ARC > > select ARCH_HAS_SETUP_DMA_OPS > > select ARCH_HAS_SYNC_DMA_FOR_CPU > > select ARCH_HAS_SYNC_DMA_FOR_DEVICE > > + select ARCH_NEED_CMPXCHG_1_EMU > > select ARCH_SUPPORTS_ATOMIC_RMW if ARC_HAS_LLSC > > select ARCH_32BIT_OFF_T > > select BUILDTIME_TABLE_SORT > > diff --git a/arch/arc/include/asm/cmpxchg.h b/arch/arc/include/asm/cmpxchg.h > > index e138fde067dea..2102ce076f28b 100644 > > --- a/arch/arc/include/asm/cmpxchg.h > > +++ b/arch/arc/include/asm/cmpxchg.h > > @@ -8,6 +8,7 @@ > > > > #include <linux/build_bug.h> > > #include <linux/types.h> > > +#include <linux/cmpxchg-emu.h> > > > > #include <asm/barrier.h> > > #include <asm/smp.h> > > @@ -46,6 +47,9 @@ > > __typeof__(*(ptr)) _prev_; \ > > \ > > switch(sizeof((_p_))) { \ > > + case 1: \ > > + _prev_ = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)_p_, (uintptr_t)_o_, (uintptr_t)_n_); \ > > + break; \ > > case 4: \ > > _prev_ = __cmpxchg(_p_, _o_, _n_); \ > > break; \ > > @@ -65,16 +69,27 @@ > > __typeof__(*(ptr)) _prev_; \ > > unsigned long __flags; \ > > \ > > - BUILD_BUG_ON(sizeof(_p_) != 4); \ > > Is this alone not sufficient: i.e. for !LLSC let the atomic op happen > under a spin-lock for non 4 byte quantities as well. Now that you mention it, that would be a lot simpler. > > + switch(sizeof((_p_))) { \ > > + case 1: \ > > + __flags = cmpxchg_emu_u8((volatile u8 *)_p_, (uintptr_t)_o_, (uintptr_t)_n_); \ > > + _prev_ = (__typeof__(*(ptr)))__flags; \ > > + break; \ > > + break; \ > > FWIW, the 2nd break seems extraneous. And to your earlier point, the first break as well. ;-) How does the updated patch below look? Or did I miss your point? Thanx, Paul ------------------------------------------------------------------------ commit 96c1107797ca329fe203818cdfda2fe5f5a9a82e Author: Paul E. McKenney <paulmck@kernel.org> Date: Mon Mar 18 01:27:35 2024 -0700 ARC: Emulate one-byte cmpxchg Use the new cmpxchg_emu_u8() to emulate one-byte cmpxchg() on arc. [ paulmck: Drop two-byte support per Arnd Bergmann feedback. ] [ paulmck: Apply feedback from Naresh Kamboju. ] [ paulmck: Apply kernel test robot feedback. ] [ paulmck: Apply feedback from Vineet Gupta. ] Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Cc: Vineet Gupta <vgupta@kernel.org> Cc: Andi Shyti <andi.shyti@linux.intel.com> Cc: Andrzej Hajda <andrzej.hajda@intel.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Palmer Dabbelt <palmer@rivosinc.com> Cc: <linux-snps-arc@lists.infradead.org> diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig index fd0b0a0d4686a..163608fd49d18 100644 --- a/arch/arc/Kconfig +++ b/arch/arc/Kconfig @@ -13,6 +13,7 @@ config ARC select ARCH_HAS_SETUP_DMA_OPS select ARCH_HAS_SYNC_DMA_FOR_CPU select ARCH_HAS_SYNC_DMA_FOR_DEVICE + select ARCH_NEED_CMPXCHG_1_EMU select ARCH_SUPPORTS_ATOMIC_RMW if ARC_HAS_LLSC select ARCH_32BIT_OFF_T select BUILDTIME_TABLE_SORT diff --git a/arch/arc/include/asm/cmpxchg.h b/arch/arc/include/asm/cmpxchg.h index e138fde067dea..58045c8983404 100644 --- a/arch/arc/include/asm/cmpxchg.h +++ b/arch/arc/include/asm/cmpxchg.h @@ -8,6 +8,7 @@ #include <linux/build_bug.h> #include <linux/types.h> +#include <linux/cmpxchg-emu.h> #include <asm/barrier.h> #include <asm/smp.h> @@ -46,6 +47,9 @@ __typeof__(*(ptr)) _prev_; \ \ switch(sizeof((_p_))) { \ + case 1: \ + _prev_ = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)_p_, (uintptr_t)_o_, (uintptr_t)_n_); \ + break; \ case 4: \ _prev_ = __cmpxchg(_p_, _o_, _n_); \ break; \ @@ -65,8 +69,6 @@ __typeof__(*(ptr)) _prev_; \ unsigned long __flags; \ \ - BUILD_BUG_ON(sizeof(_p_) != 4); \ - \ /* \ * spin lock/unlock provide the needed smp_mb() before/after \ */ \
On 8/5/24 21:28, Paul E. McKenney wrote: > On Mon, Aug 05, 2024 at 06:27:57PM -0700, Vineet Gupta wrote: >> Hi Paul, >> >> On 8/5/24 12:21, Paul E. McKenney wrote: >>> Use the new cmpxchg_emu_u8() to emulate one-byte cmpxchg() on arc. >>> >>> [ paulmck: Drop two-byte support per Arnd Bergmann feedback. ] >>> [ paulmck: Apply feedback from Naresh Kamboju. ] >>> [ paulmck: Apply kernel test robot feedback. ] >>> >>> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> >>> Cc: Vineet Gupta <vgupta@kernel.org> >>> Cc: Andi Shyti <andi.shyti@linux.intel.com> >>> Cc: Andrzej Hajda <andrzej.hajda@intel.com> >>> Cc: Arnd Bergmann <arnd@arndb.de> >>> Cc: Palmer Dabbelt <palmer@rivosinc.com> >>> Cc: <linux-snps-arc@lists.infradead.org> >>> --- >>> arch/arc/Kconfig | 1 + >>> arch/arc/include/asm/cmpxchg.h | 33 ++++++++++++++++++++++++--------- >>> 2 files changed, 25 insertions(+), 9 deletions(-) >>> >>> diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig >>> index fd0b0a0d4686a..163608fd49d18 100644 >>> --- a/arch/arc/Kconfig >>> +++ b/arch/arc/Kconfig >>> @@ -13,6 +13,7 @@ config ARC >>> select ARCH_HAS_SETUP_DMA_OPS >>> select ARCH_HAS_SYNC_DMA_FOR_CPU >>> select ARCH_HAS_SYNC_DMA_FOR_DEVICE >>> + select ARCH_NEED_CMPXCHG_1_EMU >>> select ARCH_SUPPORTS_ATOMIC_RMW if ARC_HAS_LLSC >>> select ARCH_32BIT_OFF_T >>> select BUILDTIME_TABLE_SORT >>> diff --git a/arch/arc/include/asm/cmpxchg.h b/arch/arc/include/asm/cmpxchg.h >>> index e138fde067dea..2102ce076f28b 100644 >>> --- a/arch/arc/include/asm/cmpxchg.h >>> +++ b/arch/arc/include/asm/cmpxchg.h >>> @@ -8,6 +8,7 @@ >>> >>> #include <linux/build_bug.h> >>> #include <linux/types.h> >>> +#include <linux/cmpxchg-emu.h> >>> >>> #include <asm/barrier.h> >>> #include <asm/smp.h> >>> @@ -46,6 +47,9 @@ >>> __typeof__(*(ptr)) _prev_; \ >>> \ >>> switch(sizeof((_p_))) { \ >>> + case 1: \ >>> + _prev_ = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)_p_, (uintptr_t)_o_, (uintptr_t)_n_); \ >>> + break; \ >>> case 4: \ >>> _prev_ = __cmpxchg(_p_, _o_, _n_); \ >>> break; \ >>> @@ -65,16 +69,27 @@ >>> __typeof__(*(ptr)) _prev_; \ >>> unsigned long __flags; \ >>> \ >>> - BUILD_BUG_ON(sizeof(_p_) != 4); \ >> Is this alone not sufficient: i.e. for !LLSC let the atomic op happen >> under a spin-lock for non 4 byte quantities as well. > Now that you mention it, that would be a lot simpler. > >>> + switch(sizeof((_p_))) { \ >>> + case 1: \ >>> + __flags = cmpxchg_emu_u8((volatile u8 *)_p_, (uintptr_t)_o_, (uintptr_t)_n_); \ >>> + _prev_ = (__typeof__(*(ptr)))__flags; \ >>> + break; \ >>> + break; \ >> FWIW, the 2nd break seems extraneous. > And to your earlier point, the first break as well. ;-) > > How does the updated patch below look? Or did I miss your point? > > Thanx, Paul > > ------------------------------------------------------------------------ > > commit 96c1107797ca329fe203818cdfda2fe5f5a9a82e > Author: Paul E. McKenney <paulmck@kernel.org> > Date: Mon Mar 18 01:27:35 2024 -0700 > > ARC: Emulate one-byte cmpxchg > > Use the new cmpxchg_emu_u8() to emulate one-byte cmpxchg() on arc. > > [ paulmck: Drop two-byte support per Arnd Bergmann feedback. ] > [ paulmck: Apply feedback from Naresh Kamboju. ] > [ paulmck: Apply kernel test robot feedback. ] > [ paulmck: Apply feedback from Vineet Gupta. ] > > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > Cc: Vineet Gupta <vgupta@kernel.org> > Cc: Andi Shyti <andi.shyti@linux.intel.com> > Cc: Andrzej Hajda <andrzej.hajda@intel.com> > Cc: Arnd Bergmann <arnd@arndb.de> > Cc: Palmer Dabbelt <palmer@rivosinc.com> > Cc: <linux-snps-arc@lists.infradead.org> Acked-by: Vineet Gupta <vgupta@kernel.org> Thx, -Vineet > > diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig > index fd0b0a0d4686a..163608fd49d18 100644 > --- a/arch/arc/Kconfig > +++ b/arch/arc/Kconfig > @@ -13,6 +13,7 @@ config ARC > select ARCH_HAS_SETUP_DMA_OPS > select ARCH_HAS_SYNC_DMA_FOR_CPU > select ARCH_HAS_SYNC_DMA_FOR_DEVICE > + select ARCH_NEED_CMPXCHG_1_EMU > select ARCH_SUPPORTS_ATOMIC_RMW if ARC_HAS_LLSC > select ARCH_32BIT_OFF_T > select BUILDTIME_TABLE_SORT > diff --git a/arch/arc/include/asm/cmpxchg.h b/arch/arc/include/asm/cmpxchg.h > index e138fde067dea..58045c8983404 100644 > --- a/arch/arc/include/asm/cmpxchg.h > +++ b/arch/arc/include/asm/cmpxchg.h > @@ -8,6 +8,7 @@ > > #include <linux/build_bug.h> > #include <linux/types.h> > +#include <linux/cmpxchg-emu.h> > > #include <asm/barrier.h> > #include <asm/smp.h> > @@ -46,6 +47,9 @@ > __typeof__(*(ptr)) _prev_; \ > \ > switch(sizeof((_p_))) { \ > + case 1: \ > + _prev_ = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)_p_, (uintptr_t)_o_, (uintptr_t)_n_); \ > + break; \ > case 4: \ > _prev_ = __cmpxchg(_p_, _o_, _n_); \ > break; \ > @@ -65,8 +69,6 @@ > __typeof__(*(ptr)) _prev_; \ > unsigned long __flags; \ > \ > - BUILD_BUG_ON(sizeof(_p_) != 4); \ > - \ > /* \ > * spin lock/unlock provide the needed smp_mb() before/after \ > */ \
On Mon, Aug 05, 2024 at 09:44:39PM -0700, Vineet Gupta wrote: > > > On 8/5/24 21:28, Paul E. McKenney wrote: > > On Mon, Aug 05, 2024 at 06:27:57PM -0700, Vineet Gupta wrote: > >> Hi Paul, > >> > >> On 8/5/24 12:21, Paul E. McKenney wrote: > >>> Use the new cmpxchg_emu_u8() to emulate one-byte cmpxchg() on arc. > >>> > >>> [ paulmck: Drop two-byte support per Arnd Bergmann feedback. ] > >>> [ paulmck: Apply feedback from Naresh Kamboju. ] > >>> [ paulmck: Apply kernel test robot feedback. ] > >>> > >>> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > >>> Cc: Vineet Gupta <vgupta@kernel.org> > >>> Cc: Andi Shyti <andi.shyti@linux.intel.com> > >>> Cc: Andrzej Hajda <andrzej.hajda@intel.com> > >>> Cc: Arnd Bergmann <arnd@arndb.de> > >>> Cc: Palmer Dabbelt <palmer@rivosinc.com> > >>> Cc: <linux-snps-arc@lists.infradead.org> > >>> --- > >>> arch/arc/Kconfig | 1 + > >>> arch/arc/include/asm/cmpxchg.h | 33 ++++++++++++++++++++++++--------- > >>> 2 files changed, 25 insertions(+), 9 deletions(-) > >>> > >>> diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig > >>> index fd0b0a0d4686a..163608fd49d18 100644 > >>> --- a/arch/arc/Kconfig > >>> +++ b/arch/arc/Kconfig > >>> @@ -13,6 +13,7 @@ config ARC > >>> select ARCH_HAS_SETUP_DMA_OPS > >>> select ARCH_HAS_SYNC_DMA_FOR_CPU > >>> select ARCH_HAS_SYNC_DMA_FOR_DEVICE > >>> + select ARCH_NEED_CMPXCHG_1_EMU > >>> select ARCH_SUPPORTS_ATOMIC_RMW if ARC_HAS_LLSC > >>> select ARCH_32BIT_OFF_T > >>> select BUILDTIME_TABLE_SORT > >>> diff --git a/arch/arc/include/asm/cmpxchg.h b/arch/arc/include/asm/cmpxchg.h > >>> index e138fde067dea..2102ce076f28b 100644 > >>> --- a/arch/arc/include/asm/cmpxchg.h > >>> +++ b/arch/arc/include/asm/cmpxchg.h > >>> @@ -8,6 +8,7 @@ > >>> > >>> #include <linux/build_bug.h> > >>> #include <linux/types.h> > >>> +#include <linux/cmpxchg-emu.h> > >>> > >>> #include <asm/barrier.h> > >>> #include <asm/smp.h> > >>> @@ -46,6 +47,9 @@ > >>> __typeof__(*(ptr)) _prev_; \ > >>> \ > >>> switch(sizeof((_p_))) { \ > >>> + case 1: \ > >>> + _prev_ = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)_p_, (uintptr_t)_o_, (uintptr_t)_n_); \ > >>> + break; \ > >>> case 4: \ > >>> _prev_ = __cmpxchg(_p_, _o_, _n_); \ > >>> break; \ > >>> @@ -65,16 +69,27 @@ > >>> __typeof__(*(ptr)) _prev_; \ > >>> unsigned long __flags; \ > >>> \ > >>> - BUILD_BUG_ON(sizeof(_p_) != 4); \ > >> Is this alone not sufficient: i.e. for !LLSC let the atomic op happen > >> under a spin-lock for non 4 byte quantities as well. > > Now that you mention it, that would be a lot simpler. > > > >>> + switch(sizeof((_p_))) { \ > >>> + case 1: \ > >>> + __flags = cmpxchg_emu_u8((volatile u8 *)_p_, (uintptr_t)_o_, (uintptr_t)_n_); \ > >>> + _prev_ = (__typeof__(*(ptr)))__flags; \ > >>> + break; \ > >>> + break; \ > >> FWIW, the 2nd break seems extraneous. > > And to your earlier point, the first break as well. ;-) > > > > How does the updated patch below look? Or did I miss your point? > > > > Thanx, Paul > > > > ------------------------------------------------------------------------ > > > > commit 96c1107797ca329fe203818cdfda2fe5f5a9a82e > > Author: Paul E. McKenney <paulmck@kernel.org> > > Date: Mon Mar 18 01:27:35 2024 -0700 > > > > ARC: Emulate one-byte cmpxchg > > > > Use the new cmpxchg_emu_u8() to emulate one-byte cmpxchg() on arc. > > > > [ paulmck: Drop two-byte support per Arnd Bergmann feedback. ] > > [ paulmck: Apply feedback from Naresh Kamboju. ] > > [ paulmck: Apply kernel test robot feedback. ] > > [ paulmck: Apply feedback from Vineet Gupta. ] > > > > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > > Cc: Vineet Gupta <vgupta@kernel.org> > > Cc: Andi Shyti <andi.shyti@linux.intel.com> > > Cc: Andrzej Hajda <andrzej.hajda@intel.com> > > Cc: Arnd Bergmann <arnd@arndb.de> > > Cc: Palmer Dabbelt <palmer@rivosinc.com> > > Cc: <linux-snps-arc@lists.infradead.org> > > Acked-by: Vineet Gupta <vgupta@kernel.org> Thank you, and I will apply this on my next rebase. Thanx, Paul > Thx, > -Vineet > > > > > diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig > > index fd0b0a0d4686a..163608fd49d18 100644 > > --- a/arch/arc/Kconfig > > +++ b/arch/arc/Kconfig > > @@ -13,6 +13,7 @@ config ARC > > select ARCH_HAS_SETUP_DMA_OPS > > select ARCH_HAS_SYNC_DMA_FOR_CPU > > select ARCH_HAS_SYNC_DMA_FOR_DEVICE > > + select ARCH_NEED_CMPXCHG_1_EMU > > select ARCH_SUPPORTS_ATOMIC_RMW if ARC_HAS_LLSC > > select ARCH_32BIT_OFF_T > > select BUILDTIME_TABLE_SORT > > diff --git a/arch/arc/include/asm/cmpxchg.h b/arch/arc/include/asm/cmpxchg.h > > index e138fde067dea..58045c8983404 100644 > > --- a/arch/arc/include/asm/cmpxchg.h > > +++ b/arch/arc/include/asm/cmpxchg.h > > @@ -8,6 +8,7 @@ > > > > #include <linux/build_bug.h> > > #include <linux/types.h> > > +#include <linux/cmpxchg-emu.h> > > > > #include <asm/barrier.h> > > #include <asm/smp.h> > > @@ -46,6 +47,9 @@ > > __typeof__(*(ptr)) _prev_; \ > > \ > > switch(sizeof((_p_))) { \ > > + case 1: \ > > + _prev_ = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)_p_, (uintptr_t)_o_, (uintptr_t)_n_); \ > > + break; \ > > case 4: \ > > _prev_ = __cmpxchg(_p_, _o_, _n_); \ > > break; \ > > @@ -65,8 +69,6 @@ > > __typeof__(*(ptr)) _prev_; \ > > unsigned long __flags; \ > > \ > > - BUILD_BUG_ON(sizeof(_p_) != 4); \ > > - \ > > /* \ > > * spin lock/unlock provide the needed smp_mb() before/after \ > > */ \ > >
diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig index fd0b0a0d4686a..163608fd49d18 100644 --- a/arch/arc/Kconfig +++ b/arch/arc/Kconfig @@ -13,6 +13,7 @@ config ARC select ARCH_HAS_SETUP_DMA_OPS select ARCH_HAS_SYNC_DMA_FOR_CPU select ARCH_HAS_SYNC_DMA_FOR_DEVICE + select ARCH_NEED_CMPXCHG_1_EMU select ARCH_SUPPORTS_ATOMIC_RMW if ARC_HAS_LLSC select ARCH_32BIT_OFF_T select BUILDTIME_TABLE_SORT diff --git a/arch/arc/include/asm/cmpxchg.h b/arch/arc/include/asm/cmpxchg.h index e138fde067dea..2102ce076f28b 100644 --- a/arch/arc/include/asm/cmpxchg.h +++ b/arch/arc/include/asm/cmpxchg.h @@ -8,6 +8,7 @@ #include <linux/build_bug.h> #include <linux/types.h> +#include <linux/cmpxchg-emu.h> #include <asm/barrier.h> #include <asm/smp.h> @@ -46,6 +47,9 @@ __typeof__(*(ptr)) _prev_; \ \ switch(sizeof((_p_))) { \ + case 1: \ + _prev_ = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)_p_, (uintptr_t)_o_, (uintptr_t)_n_); \ + break; \ case 4: \ _prev_ = __cmpxchg(_p_, _o_, _n_); \ break; \ @@ -65,16 +69,27 @@ __typeof__(*(ptr)) _prev_; \ unsigned long __flags; \ \ - BUILD_BUG_ON(sizeof(_p_) != 4); \ + switch(sizeof((_p_))) { \ + case 1: \ + __flags = cmpxchg_emu_u8((volatile u8 *)_p_, (uintptr_t)_o_, (uintptr_t)_n_); \ + _prev_ = (__typeof__(*(ptr)))__flags; \ + break; \ + break; \ + case 4: \ + /* \ + * spin lock/unlock provide the needed smp_mb() \ + * before/after \ + */ \ + atomic_ops_lock(__flags); \ + _prev_ = *_p_; \ + if (_prev_ == _o_) \ + *_p_ = _n_; \ + atomic_ops_unlock(__flags); \ + break; \ + default: \ + BUILD_BUG(); \ + } \ \ - /* \ - * spin lock/unlock provide the needed smp_mb() before/after \ - */ \ - atomic_ops_lock(__flags); \ - _prev_ = *_p_; \ - if (_prev_ == _o_) \ - *_p_ = _n_; \ - atomic_ops_unlock(__flags); \ _prev_; \ })
Use the new cmpxchg_emu_u8() to emulate one-byte cmpxchg() on arc. [ paulmck: Drop two-byte support per Arnd Bergmann feedback. ] [ paulmck: Apply feedback from Naresh Kamboju. ] [ paulmck: Apply kernel test robot feedback. ] Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Cc: Vineet Gupta <vgupta@kernel.org> Cc: Andi Shyti <andi.shyti@linux.intel.com> Cc: Andrzej Hajda <andrzej.hajda@intel.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Palmer Dabbelt <palmer@rivosinc.com> Cc: <linux-snps-arc@lists.infradead.org> --- arch/arc/Kconfig | 1 + arch/arc/include/asm/cmpxchg.h | 33 ++++++++++++++++++++++++--------- 2 files changed, 25 insertions(+), 9 deletions(-)