From: Nick Desaulniers <ndesaulniers@google.com>
To: Brian Gerst <brgerst@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>, Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@alien8.de>,
"H . Peter Anvin" <hpa@zytor.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH v2 09/10] x86/percpu: Clean up percpu_stable_op()
Date: Mon, 1 Jun 2020 13:43:18 -0700 [thread overview]
Message-ID: <CAKwvOdmgN7xra26_xBYCJo45OdOUHLNmw16ioLOE171f_HE0eA@mail.gmail.com> (raw)
In-Reply-To: <20200530221127.459704-10-brgerst@gmail.com>
On Sat, May 30, 2020 at 3:11 PM Brian Gerst <brgerst@gmail.com> wrote:
>
> Use __pcpu_size_call_return() to simplify this_cpu_read_stable().
Clever! As in this_cpu_read() in include/linux/percpu-defs.h. Could
be its own patch before this, but it's fine.
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> Also remove __bad_percpu_size() which is now unused.
>
> Signed-off-by: Brian Gerst <brgerst@gmail.com>
> ---
> arch/x86/include/asm/percpu.h | 41 ++++++++++-------------------------
> 1 file changed, 12 insertions(+), 29 deletions(-)
>
> diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
> index 7efc0b5c4ff0..cf2b9c2a241e 100644
> --- a/arch/x86/include/asm/percpu.h
> +++ b/arch/x86/include/asm/percpu.h
> @@ -85,7 +85,6 @@
>
> /* For arch-specific code, we can use direct single-insn ops (they
> * don't give an lvalue though). */
> -extern void __bad_percpu_size(void);
>
> #define __pcpu_type_1 u8
> #define __pcpu_type_2 u16
> @@ -167,33 +166,13 @@ do { \
> (typeof(_var))(unsigned long) pfo_val__; \
> })
>
> -#define percpu_stable_op(op, var) \
> -({ \
> - typeof(var) pfo_ret__; \
> - switch (sizeof(var)) { \
> - case 1: \
> - asm(op "b "__percpu_arg(P1)",%0" \
What does the `P` do here?
https://gcc.gnu.org/onlinedocs/gcc/Simple-Constraints.html#Simple-Constraints
says can be machine dependent integral literal in a certain range.
https://gcc.gnu.org/onlinedocs/gcc/Machine-Constraints.html#Machine-Constraints
doesn't document `P` for x86 though...
> - : "=q" (pfo_ret__) \
> - : "p" (&(var))); \
> - break; \
> - case 2: \
> - asm(op "w "__percpu_arg(P1)",%0" \
> - : "=r" (pfo_ret__) \
> - : "p" (&(var))); \
> - break; \
> - case 4: \
> - asm(op "l "__percpu_arg(P1)",%0" \
> - : "=r" (pfo_ret__) \
> - : "p" (&(var))); \
> - break; \
> - case 8: \
> - asm(op "q "__percpu_arg(P1)",%0" \
> - : "=r" (pfo_ret__) \
> - : "p" (&(var))); \
> - break; \
> - default: __bad_percpu_size(); \
> - } \
> - pfo_ret__; \
> +#define percpu_stable_op(size, op, _var) \
> +({ \
> + __pcpu_type_##size pfo_val__; \
> + asm(__pcpu_op2_##size(op, __percpu_arg(P[var]), "%[val]") \
> + : [val] __pcpu_reg_##size("=", pfo_val__) \
> + : [var] "p" (&(_var))); \
> + (typeof(_var))(unsigned long) pfo_val__; \
> })
>
> /*
> @@ -258,7 +237,11 @@ do { \
> * per-thread variables implemented as per-cpu variables and thus
> * stable for the duration of the respective task.
> */
> -#define this_cpu_read_stable(var) percpu_stable_op("mov", var)
> +#define this_cpu_read_stable_1(pcp) percpu_stable_op(1, "mov", pcp)
> +#define this_cpu_read_stable_2(pcp) percpu_stable_op(2, "mov", pcp)
> +#define this_cpu_read_stable_4(pcp) percpu_stable_op(4, "mov", pcp)
> +#define this_cpu_read_stable_8(pcp) percpu_stable_op(8, "mov", pcp)
> +#define this_cpu_read_stable(pcp) __pcpu_size_call_return(this_cpu_read_stable_, pcp)
>
> #define raw_cpu_read_1(pcp) percpu_from_op(1, , "mov", pcp)
> #define raw_cpu_read_2(pcp) percpu_from_op(2, , "mov", pcp)
> --
> 2.25.4
>
--
Thanks,
~Nick Desaulniers
next prev parent reply other threads:[~2020-06-01 20:43 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-30 22:11 [PATCH v2 00/10] x86: Clean up percpu operations Brian Gerst
2020-05-30 22:11 ` [PATCH v2 01/10] x86/percpu: Introduce size abstraction macros Brian Gerst
2020-06-01 20:48 ` Nick Desaulniers
2020-05-30 22:11 ` [PATCH v2 02/10] x86/percpu: Clean up percpu_to_op() Brian Gerst
2020-07-09 10:30 ` Peter Zijlstra
2020-07-10 4:38 ` Brian Gerst
2020-07-10 8:53 ` Peter Zijlstra
2020-07-10 16:56 ` Nick Desaulniers
2020-05-30 22:11 ` [PATCH v2 03/10] x86/percpu: Clean up percpu_from_op() Brian Gerst
2020-05-30 22:11 ` [PATCH v2 04/10] x86/percpu: Clean up percpu_add_op() Brian Gerst
2020-06-01 20:18 ` Nick Desaulniers
2020-05-30 22:11 ` [PATCH v2 05/10] x86/percpu: Remove "e" constraint from XADD Brian Gerst
2020-06-01 18:50 ` Nick Desaulniers
2020-05-30 22:11 ` [PATCH v2 06/10] x86/percpu: Clean up percpu_add_return_op() Brian Gerst
2020-06-01 19:47 ` Nick Desaulniers
2020-05-30 22:11 ` [PATCH v2 07/10] x86/percpu: Clean up percpu_xchg_op() Brian Gerst
2020-05-30 22:11 ` [PATCH v2 08/10] x86/percpu: Clean up percpu_cmpxchg_op() Brian Gerst
2020-05-30 22:11 ` [PATCH v2 09/10] x86/percpu: Clean up percpu_stable_op() Brian Gerst
2020-06-01 20:43 ` Nick Desaulniers [this message]
2020-06-02 14:19 ` Brian Gerst
2020-07-09 10:25 ` Peter Zijlstra
2020-05-30 22:11 ` [PATCH v2 10/10] x86/percpu: Remove unused PER_CPU() macro Brian Gerst
2020-06-01 20:26 ` Nick Desaulniers
2020-06-01 21:00 ` [PATCH v2 00/10] x86: Clean up percpu operations Nick Desaulniers
2020-07-08 19:36 ` Nick Desaulniers
2020-07-09 20:02 ` Nick Desaulniers
2020-07-13 22:24 ` Nick Desaulniers
2020-07-13 22:40 ` Linus Torvalds
2020-07-13 22:58 ` Nick Desaulniers
2020-07-14 0:31 ` Nick Desaulniers
2020-07-14 1:29 ` Linus Torvalds
2020-07-09 10:30 ` Peter Zijlstra
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