Re: [PATCH v3 1/5] arch,locking/atomic: arc: arch_cmpxchg should check data size
Hi Wuqiang,
On Tue, Nov 21, 2023 at 10:23:43PM +0800, wuqiang.matt wrote:
> arch_cmpxchg() should check data size rather than pointer size in case
> CONFIG_ARC_HAS_LLSC is defined. So rename __cmpxchg to __cmpxchg_32 to
> emphasize it's explicit support of 32bit data size with BUILD_BUG_ON()
> added to avoid any possible misuses with unsupported data types.
>
> In case CONFIG_ARC_HAS_LLSC is undefined, arch_cmpxchg() uses spinlock
> to accomplish SMP-safety, so the BUILD_BUG_ON checking is uncecessary.
>
> v2 -> v3:
> - Patches regrouped and has the improvement for xtensa included
> - Comments refined to address why these changes are needed
>
> v1 -> v2:
> - Try using native cmpxchg variants if avaialble, as Arnd advised
>
> Signed-off-by: wuqiang.matt
> Reviewed-by: Masami Hiramatsu (Google)
> ---
> arch/arc/include/asm/cmpxchg.h | 12 ++--
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arc/include/asm/cmpxchg.h b/arch/arc/include/asm/cmpxchg.h
> index e138fde067de..bf46514f6f12 100644
> --- a/arch/arc/include/asm/cmpxchg.h
> +++ b/arch/arc/include/asm/cmpxchg.h
> @@ -18,14 +18,16 @@
> * if (*ptr == @old)
> * *ptr = @new
> */
> -#define __cmpxchg(ptr, old, new) \
> +#define __cmpxchg_32(ptr, old, new) \
> ({ \
> __typeof__(*(ptr)) _prev; \
> \
> + BUILD_BUG_ON(sizeof(*(ptr)) != 4); \
> + \
> __asm__ __volatile__( \
> - "1: llock %0, [%1] \n" \
> + "1: llock %0, [%1] \n" \
> " brne %0, %2, 2f \n" \
> - " scond %3, [%1] \n" \
> + " scond %3, [%1] \n" \
> " bnz 1b \n" \
> "2: \n" \
> : "="(_prev) /* Early clobber prevent reg reuse */ \
> @@ -47,7 +49,7 @@
> \
> switch(sizeof((_p_))) { \
> case 4: \
> - _prev_ = __cmpxchg(_p_, _o_, _n_); \
> + _prev_ = __cmpxchg_32(_p_, _o_, _n_); \
> break; \
> default:\
> BUILD_BUG();\
> @@ -65,8 +67,6 @@
> __typeof__(*(ptr)) _prev_; \
> unsigned long __flags; \
> \
> - BUILD_BUG_ON(sizeof(_p_) != 4); \
> - \
I think I made some comments here that have not been addressed or
replied.
Thanks,
Andi
> /* \
>* spin lock/unlock provide the needed smp_mb() before/after\
>*/ \
> --
> 2.40.1
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Re: [Intel-gfx] [PATCH v5 5/7] io_uring: use __xchg if possible
Hi Andrzej, On Wed, Jan 18, 2023 at 04:44:48PM +0100, Andrzej Hajda wrote: > Recently introduced helper simplifies the code. > > Signed-off-by: Andrzej Hajda Reviewed-by: Andi Shyti Thanks, Andi ___ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc
Re: [Intel-gfx] [PATCH v5 7/7] drm/i915/gt: use __xchg instead of internal helper
Hi Andrzej, On Wed, Jan 18, 2023 at 04:44:50PM +0100, Andrzej Hajda wrote: > Prefer core helper if available. > > Signed-off-by: Andrzej Hajda Reviewed-by: Andi Shyti Thanks, Andi ___ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc
Re: [Intel-gfx] [PATCH v5 6/7] qed: use __xchg if possible
Hi Andrzej, On Wed, Jan 18, 2023 at 04:44:49PM +0100, Andrzej Hajda wrote: > Recently introduced helper simplifies the code. > > Signed-off-by: Andrzej Hajda Reviewed-by: Andi Shyti Thanks, Andi ___ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc
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Re: [Intel-gfx] [PATCH v5 3/7] arch/*/uprobes: simplify arch_uretprobe_hijack_return_addr
Hi Andrzej, On Wed, Jan 18, 2023 at 04:44:46PM +0100, Andrzej Hajda wrote: > In all architectures, except x86, arch_uretprobe_hijack_return_addr > is just __xchg. > > Signed-off-by: Andrzej Hajda Reviewed-by: Andi Shyti Thanks, Andi ___ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc
Re: [Intel-gfx] [PATCH v5 2/7] linux/include: add non-atomic version of xchg
Hi Andrzej, On Wed, Jan 18, 2023 at 04:44:45PM +0100, Andrzej Hajda wrote: > The pattern of setting variable with new value and returning old > one is very common in kernel. Usually atomicity of the operation > is not required, so xchg seems to be suboptimal and confusing in > such cases. > > Signed-off-by: Andrzej Hajda > Reviewed-by: Andy Shevchenko Reviewed-by: Andi Shyti Thanks, Andi ___ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc
Re: [Intel-gfx] [PATCH v5 1/7] arch: rename all internal names __xchg to __arch_xchg
Hi Andrzej, On Wed, Jan 18, 2023 at 04:44:44PM +0100, Andrzej Hajda wrote: > __xchg will be used for non-atomic xchg macro. > > Signed-off-by: Andrzej Hajda > Reviewed-by: Arnd Bergmann > Acked-by: Geert Uytterhoeven [m68k] > Acked-by: Palmer Dabbelt [riscv] Reviewed-by: Andi Shyti Thanks, Andi ___ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc
