From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932466AbeCIR42 (ORCPT ); Fri, 9 Mar 2018 12:56:28 -0500 Received: from mail-pl0-f66.google.com ([209.85.160.66]:40761 "EHLO mail-pl0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932408AbeCIR4Y (ORCPT ); Fri, 9 Mar 2018 12:56:24 -0500 X-Google-Smtp-Source: AG47ELtV1hLMc+GC7WPGo0RCE4UA860XF9XYhXbuCCjGRLgL7UUDTjoP+1LfaWpnp8TVBb26l0bTTA== Date: Fri, 09 Mar 2018 09:56:21 -0800 (PST) X-Google-Original-Date: Fri, 09 Mar 2018 09:56:16 PST (-0800) Subject: Re: [PATCH v2 2/2] riscv/atomic: Strengthen implementations with fences In-Reply-To: <1520597620-16650-1-git-send-email-parri.andrea@gmail.com> CC: albert@sifive.com, Daniel Lustig , stern@rowland.harvard.edu, Will Deacon , peterz@infradead.org, boqun.feng@gmail.com, npiggin@gmail.com, dhowells@redhat.com, j.alglave@ucl.ac.uk, luc.maranget@inria.fr, paulmck@linux.vnet.ibm.com, akiyks@gmail.com, mingo@kernel.org, Linus Torvalds , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, parri.andrea@gmail.com From: Palmer Dabbelt To: parri.andrea@gmail.com Message-ID: Mime-Version: 1.0 (MHng) Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 09 Mar 2018 04:13:40 PST (-0800), parri.andrea@gmail.com wrote: > Atomics present the same issue with locking: release and acquire > variants need to be strengthened to meet the constraints defined > by the Linux-kernel memory consistency model [1]. > > Atomics present a further issue: implementations of atomics such > as atomic_cmpxchg() and atomic_add_unless() rely on LR/SC pairs, > which do not give full-ordering with .aqrl; for example, current > implementations allow the "lr-sc-aqrl-pair-vs-full-barrier" test > below to end up with the state indicated in the "exists" clause. > > In order to "synchronize" LKMM and RISC-V's implementation, this > commit strengthens the implementations of the atomics operations > by replacing .rl and .aq with the use of ("lightweigth") fences, > and by replacing .aqrl LR/SC pairs in sequences such as: > > 0: lr.w.aqrl %0, %addr > bne %0, %old, 1f > ... > sc.w.aqrl %1, %new, %addr > bnez %1, 0b > 1: > > with sequences of the form: > > 0: lr.w %0, %addr > bne %0, %old, 1f > ... > sc.w.rl %1, %new, %addr /* SC-release */ > bnez %1, 0b > fence rw, rw /* "full" fence */ > 1: > > following Daniel's suggestion. > > These modifications were validated with simulation of the RISC-V > memory consistency model. > > C lr-sc-aqrl-pair-vs-full-barrier > > {} > > P0(int *x, int *y, atomic_t *u) > { > int r0; > int r1; > > WRITE_ONCE(*x, 1); > r0 = atomic_cmpxchg(u, 0, 1); > r1 = READ_ONCE(*y); > } > > P1(int *x, int *y, atomic_t *v) > { > int r0; > int r1; > > WRITE_ONCE(*y, 1); > r0 = atomic_cmpxchg(v, 0, 1); > r1 = READ_ONCE(*x); > } > > exists (u=1 /\ v=1 /\ 0:r1=0 /\ 1:r1=0) > > [1] https://marc.info/?l=linux-kernel&m=151930201102853&w=2 > https://groups.google.com/a/groups.riscv.org/forum/#!topic/isa-dev/hKywNHBkAXM > https://marc.info/?l=linux-kernel&m=151633436614259&w=2 > > Suggested-by: Daniel Lustig > Signed-off-by: Andrea Parri > Cc: Palmer Dabbelt > Cc: Albert Ou > Cc: Daniel Lustig > Cc: Alan Stern > Cc: Will Deacon > Cc: Peter Zijlstra > Cc: Boqun Feng > Cc: Nicholas Piggin > Cc: David Howells > Cc: Jade Alglave > Cc: Luc Maranget > Cc: "Paul E. McKenney" > Cc: Akira Yokosawa > Cc: Ingo Molnar > Cc: Linus Torvalds > Cc: linux-riscv@lists.infradead.org > Cc: linux-kernel@vger.kernel.org > --- > arch/riscv/include/asm/atomic.h | 417 +++++++++++++++++++++++++-------------- > arch/riscv/include/asm/cmpxchg.h | 391 +++++++++++++++++++++++++++++------- > 2 files changed, 588 insertions(+), 220 deletions(-) > > diff --git a/arch/riscv/include/asm/atomic.h b/arch/riscv/include/asm/atomic.h > index e65d1cd89e28b..855115ace98c8 100644 > --- a/arch/riscv/include/asm/atomic.h > +++ b/arch/riscv/include/asm/atomic.h > @@ -24,6 +24,20 @@ > #include > > #define ATOMIC_INIT(i) { (i) } > + > +#define __atomic_op_acquire(op, args...) \ > +({ \ > + typeof(op##_relaxed(args)) __ret = op##_relaxed(args); \ > + __asm__ __volatile__(RISCV_ACQUIRE_BARRIER "" ::: "memory"); \ > + __ret; \ > +}) > + > +#define __atomic_op_release(op, args...) \ > +({ \ > + __asm__ __volatile__(RISCV_RELEASE_BARRIER "" ::: "memory"); \ > + op##_relaxed(args); \ > +}) > + > static __always_inline int atomic_read(const atomic_t *v) > { > return READ_ONCE(v->counter); > @@ -50,22 +64,23 @@ static __always_inline void atomic64_set(atomic64_t *v, long i) > * have the AQ or RL bits set. These don't return anything, so there's only > * one version to worry about. > */ > -#define ATOMIC_OP(op, asm_op, I, asm_type, c_type, prefix) \ > -static __always_inline void atomic##prefix##_##op(c_type i, atomic##prefix##_t *v) \ > -{ \ > - __asm__ __volatile__ ( \ > - "amo" #asm_op "." #asm_type " zero, %1, %0" \ > - : "+A" (v->counter) \ > - : "r" (I) \ > - : "memory"); \ > -} > +#define ATOMIC_OP(op, asm_op, I, asm_type, c_type, prefix) \ > +static __always_inline \ > +void atomic##prefix##_##op(c_type i, atomic##prefix##_t *v) \ > +{ \ > + __asm__ __volatile__ ( \ > + " amo" #asm_op "." #asm_type " zero, %1, %0" \ > + : "+A" (v->counter) \ > + : "r" (I) \ > + : "memory"); \ > +} \ Just to be sure: this is just a whitespace change, right? > #ifdef CONFIG_GENERIC_ATOMIC64 > -#define ATOMIC_OPS(op, asm_op, I) \ > +#define ATOMIC_OPS(op, asm_op, I) \ > ATOMIC_OP (op, asm_op, I, w, int, ) > #else > -#define ATOMIC_OPS(op, asm_op, I) \ > - ATOMIC_OP (op, asm_op, I, w, int, ) \ > +#define ATOMIC_OPS(op, asm_op, I) \ > + ATOMIC_OP (op, asm_op, I, w, int, ) \ > ATOMIC_OP (op, asm_op, I, d, long, 64) > #endif > > @@ -79,75 +94,115 @@ ATOMIC_OPS(xor, xor, i) > #undef ATOMIC_OPS > > /* > - * Atomic ops that have ordered, relaxed, acquire, and relese variants. > + * Atomic ops that have ordered, relaxed, acquire, and release variants. > * There's two flavors of these: the arithmatic ops have both fetch and return > * versions, while the logical ops only have fetch versions. > */ > -#define ATOMIC_FETCH_OP(op, asm_op, I, asm_or, c_or, asm_type, c_type, prefix) \ > -static __always_inline c_type atomic##prefix##_fetch_##op##c_or(c_type i, atomic##prefix##_t *v) \ > -{ \ > - register c_type ret; \ > - __asm__ __volatile__ ( \ > - "amo" #asm_op "." #asm_type #asm_or " %1, %2, %0" \ > - : "+A" (v->counter), "=r" (ret) \ > - : "r" (I) \ > - : "memory"); \ > - return ret; \ > +#define ATOMIC_FETCH_OP(op, asm_op, I, asm_type, c_type, prefix) \ > +static __always_inline \ > +c_type atomic##prefix##_fetch_##op##_relaxed(c_type i, \ > + atomic##prefix##_t *v) \ > +{ \ > + register c_type ret; \ > + __asm__ __volatile__ ( \ > + " amo" #asm_op "." #asm_type " %1, %2, %0" \ > + : "+A" (v->counter), "=r" (ret) \ > + : "r" (I) \ > + : "memory"); \ > + return ret; \ > +} \ > +static __always_inline \ > +c_type atomic##prefix##_fetch_##op(c_type i, atomic##prefix##_t *v) \ > +{ \ > + register c_type ret; \ > + __asm__ __volatile__ ( \ > + " amo" #asm_op "." #asm_type ".aqrl %1, %2, %0" \ > + : "+A" (v->counter), "=r" (ret) \ > + : "r" (I) \ > + : "memory"); \ > + return ret; \ > } > > -#define ATOMIC_OP_RETURN(op, asm_op, c_op, I, asm_or, c_or, asm_type, c_type, prefix) \ > -static __always_inline c_type atomic##prefix##_##op##_return##c_or(c_type i, atomic##prefix##_t *v) \ > -{ \ > - return atomic##prefix##_fetch_##op##c_or(i, v) c_op I; \ > +#define ATOMIC_OP_RETURN(op, asm_op, c_op, I, asm_type, c_type, prefix) \ > +static __always_inline \ > +c_type atomic##prefix##_##op##_return_relaxed(c_type i, \ > + atomic##prefix##_t *v) \ > +{ \ > + return atomic##prefix##_fetch_##op##_relaxed(i, v) c_op I; \ > +} \ > +static __always_inline \ > +c_type atomic##prefix##_##op##_return(c_type i, atomic##prefix##_t *v) \ > +{ \ > + return atomic##prefix##_fetch_##op(i, v) c_op I; \ > } > > #ifdef CONFIG_GENERIC_ATOMIC64 > -#define ATOMIC_OPS(op, asm_op, c_op, I, asm_or, c_or) \ > - ATOMIC_FETCH_OP (op, asm_op, I, asm_or, c_or, w, int, ) \ > - ATOMIC_OP_RETURN(op, asm_op, c_op, I, asm_or, c_or, w, int, ) > +#define ATOMIC_OPS(op, asm_op, c_op, I) \ > + ATOMIC_FETCH_OP( op, asm_op, I, w, int, ) \ > + ATOMIC_OP_RETURN(op, asm_op, c_op, I, w, int, ) > #else > -#define ATOMIC_OPS(op, asm_op, c_op, I, asm_or, c_or) \ > - ATOMIC_FETCH_OP (op, asm_op, I, asm_or, c_or, w, int, ) \ > - ATOMIC_OP_RETURN(op, asm_op, c_op, I, asm_or, c_or, w, int, ) \ > - ATOMIC_FETCH_OP (op, asm_op, I, asm_or, c_or, d, long, 64) \ > - ATOMIC_OP_RETURN(op, asm_op, c_op, I, asm_or, c_or, d, long, 64) > +#define ATOMIC_OPS(op, asm_op, c_op, I) \ > + ATOMIC_FETCH_OP( op, asm_op, I, w, int, ) \ > + ATOMIC_OP_RETURN(op, asm_op, c_op, I, w, int, ) \ > + ATOMIC_FETCH_OP( op, asm_op, I, d, long, 64) \ > + ATOMIC_OP_RETURN(op, asm_op, c_op, I, d, long, 64) > #endif > > -ATOMIC_OPS(add, add, +, i, , _relaxed) > -ATOMIC_OPS(add, add, +, i, .aq , _acquire) > -ATOMIC_OPS(add, add, +, i, .rl , _release) > -ATOMIC_OPS(add, add, +, i, .aqrl, ) > +ATOMIC_OPS(add, add, +, i) > +ATOMIC_OPS(sub, add, +, -i) Sorry, I must be missing something, but how do the acquire and release atomics get generated with this new code? > + > +#define atomic_add_return_relaxed atomic_add_return_relaxed > +#define atomic_sub_return_relaxed atomic_sub_return_relaxed > +#define atomic_add_return atomic_add_return > +#define atomic_sub_return atomic_sub_return > > -ATOMIC_OPS(sub, add, +, -i, , _relaxed) > -ATOMIC_OPS(sub, add, +, -i, .aq , _acquire) > -ATOMIC_OPS(sub, add, +, -i, .rl , _release) > -ATOMIC_OPS(sub, add, +, -i, .aqrl, ) > +#define atomic_fetch_add_relaxed atomic_fetch_add_relaxed > +#define atomic_fetch_sub_relaxed atomic_fetch_sub_relaxed > +#define atomic_fetch_add atomic_fetch_add > +#define atomic_fetch_sub atomic_fetch_sub > + > +#ifndef CONFIG_GENERIC_ATOMIC64 > +#define atomic64_add_return_relaxed atomic64_add_return_relaxed > +#define atomic64_sub_return_relaxed atomic64_sub_return_relaxed > +#define atomic64_add_return atomic64_add_return > +#define atomic64_sub_return atomic64_sub_return > + > +#define atomic64_fetch_add_relaxed atomic64_fetch_add_relaxed > +#define atomic64_fetch_sub_relaxed atomic64_fetch_sub_relaxed > +#define atomic64_fetch_add atomic64_fetch_add > +#define atomic64_fetch_sub atomic64_fetch_sub > +#endif > > #undef ATOMIC_OPS > > #ifdef CONFIG_GENERIC_ATOMIC64 > -#define ATOMIC_OPS(op, asm_op, I, asm_or, c_or) \ > - ATOMIC_FETCH_OP(op, asm_op, I, asm_or, c_or, w, int, ) > +#define ATOMIC_OPS(op, asm_op, I) \ > + ATOMIC_FETCH_OP(op, asm_op, I, w, int, ) > #else > -#define ATOMIC_OPS(op, asm_op, I, asm_or, c_or) \ > - ATOMIC_FETCH_OP(op, asm_op, I, asm_or, c_or, w, int, ) \ > - ATOMIC_FETCH_OP(op, asm_op, I, asm_or, c_or, d, long, 64) > +#define ATOMIC_OPS(op, asm_op, I) \ > + ATOMIC_FETCH_OP(op, asm_op, I, w, int, ) \ > + ATOMIC_FETCH_OP(op, asm_op, I, d, long, 64) > #endif > > -ATOMIC_OPS(and, and, i, , _relaxed) > -ATOMIC_OPS(and, and, i, .aq , _acquire) > -ATOMIC_OPS(and, and, i, .rl , _release) > -ATOMIC_OPS(and, and, i, .aqrl, ) > +ATOMIC_OPS(and, and, i) > +ATOMIC_OPS( or, or, i) > +ATOMIC_OPS(xor, xor, i) > > -ATOMIC_OPS( or, or, i, , _relaxed) > -ATOMIC_OPS( or, or, i, .aq , _acquire) > -ATOMIC_OPS( or, or, i, .rl , _release) > -ATOMIC_OPS( or, or, i, .aqrl, ) > +#define atomic_fetch_and_relaxed atomic_fetch_and_relaxed > +#define atomic_fetch_or_relaxed atomic_fetch_or_relaxed > +#define atomic_fetch_xor_relaxed atomic_fetch_xor_relaxed > +#define atomic_fetch_and atomic_fetch_and > +#define atomic_fetch_or atomic_fetch_or > +#define atomic_fetch_xor atomic_fetch_xor > > -ATOMIC_OPS(xor, xor, i, , _relaxed) > -ATOMIC_OPS(xor, xor, i, .aq , _acquire) > -ATOMIC_OPS(xor, xor, i, .rl , _release) > -ATOMIC_OPS(xor, xor, i, .aqrl, ) > +#ifndef CONFIG_GENERIC_ATOMIC64 > +#define atomic64_fetch_and_relaxed atomic64_fetch_and_relaxed > +#define atomic64_fetch_or_relaxed atomic64_fetch_or_relaxed > +#define atomic64_fetch_xor_relaxed atomic64_fetch_xor_relaxed > +#define atomic64_fetch_and atomic64_fetch_and > +#define atomic64_fetch_or atomic64_fetch_or > +#define atomic64_fetch_xor atomic64_fetch_xor > +#endif > > #undef ATOMIC_OPS > > @@ -157,22 +212,24 @@ ATOMIC_OPS(xor, xor, i, .aqrl, ) > /* > * The extra atomic operations that are constructed from one of the core > * AMO-based operations above (aside from sub, which is easier to fit above). > - * These are required to perform a barrier, but they're OK this way because > - * atomic_*_return is also required to perform a barrier. > + * These are required to perform a full barrier, but they're OK this way > + * because atomic_*_return is also required to perform a full barrier. > + * > */ > -#define ATOMIC_OP(op, func_op, comp_op, I, c_type, prefix) \ > -static __always_inline bool atomic##prefix##_##op(c_type i, atomic##prefix##_t *v) \ > -{ \ > - return atomic##prefix##_##func_op##_return(i, v) comp_op I; \ > +#define ATOMIC_OP(op, func_op, comp_op, I, c_type, prefix) \ > +static __always_inline \ > +bool atomic##prefix##_##op(c_type i, atomic##prefix##_t *v) \ > +{ \ > + return atomic##prefix##_##func_op##_return(i, v) comp_op I; \ > } > > #ifdef CONFIG_GENERIC_ATOMIC64 > -#define ATOMIC_OPS(op, func_op, comp_op, I) \ > - ATOMIC_OP (op, func_op, comp_op, I, int, ) > +#define ATOMIC_OPS(op, func_op, comp_op, I) \ > + ATOMIC_OP(op, func_op, comp_op, I, int, ) > #else > -#define ATOMIC_OPS(op, func_op, comp_op, I) \ > - ATOMIC_OP (op, func_op, comp_op, I, int, ) \ > - ATOMIC_OP (op, func_op, comp_op, I, long, 64) > +#define ATOMIC_OPS(op, func_op, comp_op, I) \ > + ATOMIC_OP(op, func_op, comp_op, I, int, ) \ > + ATOMIC_OP(op, func_op, comp_op, I, long, 64) > #endif > > ATOMIC_OPS(add_and_test, add, ==, 0) > @@ -182,51 +239,87 @@ ATOMIC_OPS(add_negative, add, <, 0) > #undef ATOMIC_OP > #undef ATOMIC_OPS > > -#define ATOMIC_OP(op, func_op, I, c_type, prefix) \ > -static __always_inline void atomic##prefix##_##op(atomic##prefix##_t *v) \ > -{ \ > - atomic##prefix##_##func_op(I, v); \ > +#define ATOMIC_OP(op, func_op, I, c_type, prefix) \ > +static __always_inline \ > +void atomic##prefix##_##op(atomic##prefix##_t *v) \ > +{ \ > + atomic##prefix##_##func_op(I, v); \ > } > > -#define ATOMIC_FETCH_OP(op, func_op, I, c_type, prefix) \ > -static __always_inline c_type atomic##prefix##_fetch_##op(atomic##prefix##_t *v) \ > -{ \ > - return atomic##prefix##_fetch_##func_op(I, v); \ > +#define ATOMIC_FETCH_OP(op, func_op, I, c_type, prefix) \ > +static __always_inline \ > +c_type atomic##prefix##_fetch_##op##_relaxed(atomic##prefix##_t *v) \ > +{ \ > + return atomic##prefix##_fetch_##func_op##_relaxed(I, v); \ > +} \ > +static __always_inline \ > +c_type atomic##prefix##_fetch_##op(atomic##prefix##_t *v) \ > +{ \ > + return atomic##prefix##_fetch_##func_op(I, v); \ > } > > -#define ATOMIC_OP_RETURN(op, asm_op, c_op, I, c_type, prefix) \ > -static __always_inline c_type atomic##prefix##_##op##_return(atomic##prefix##_t *v) \ > -{ \ > - return atomic##prefix##_fetch_##op(v) c_op I; \ > +#define ATOMIC_OP_RETURN(op, asm_op, c_op, I, c_type, prefix) \ > +static __always_inline \ > +c_type atomic##prefix##_##op##_return_relaxed(atomic##prefix##_t *v) \ > +{ \ > + return atomic##prefix##_fetch_##op##_relaxed(v) c_op I; \ > +} \ > +static __always_inline \ > +c_type atomic##prefix##_##op##_return(atomic##prefix##_t *v) \ > +{ \ > + return atomic##prefix##_fetch_##op(v) c_op I; \ > } > > #ifdef CONFIG_GENERIC_ATOMIC64 > -#define ATOMIC_OPS(op, asm_op, c_op, I) \ > - ATOMIC_OP (op, asm_op, I, int, ) \ > - ATOMIC_FETCH_OP (op, asm_op, I, int, ) \ > +#define ATOMIC_OPS(op, asm_op, c_op, I) \ > + ATOMIC_OP( op, asm_op, I, int, ) \ > + ATOMIC_FETCH_OP( op, asm_op, I, int, ) \ > ATOMIC_OP_RETURN(op, asm_op, c_op, I, int, ) > #else > -#define ATOMIC_OPS(op, asm_op, c_op, I) \ > - ATOMIC_OP (op, asm_op, I, int, ) \ > - ATOMIC_FETCH_OP (op, asm_op, I, int, ) \ > - ATOMIC_OP_RETURN(op, asm_op, c_op, I, int, ) \ > - ATOMIC_OP (op, asm_op, I, long, 64) \ > - ATOMIC_FETCH_OP (op, asm_op, I, long, 64) \ > +#define ATOMIC_OPS(op, asm_op, c_op, I) \ > + ATOMIC_OP( op, asm_op, I, int, ) \ > + ATOMIC_FETCH_OP( op, asm_op, I, int, ) \ > + ATOMIC_OP_RETURN(op, asm_op, c_op, I, int, ) \ > + ATOMIC_OP( op, asm_op, I, long, 64) \ > + ATOMIC_FETCH_OP( op, asm_op, I, long, 64) \ > ATOMIC_OP_RETURN(op, asm_op, c_op, I, long, 64) > #endif > > ATOMIC_OPS(inc, add, +, 1) > ATOMIC_OPS(dec, add, +, -1) > > +#define atomic_inc_return_relaxed atomic_inc_return_relaxed > +#define atomic_dec_return_relaxed atomic_dec_return_relaxed > +#define atomic_inc_return atomic_inc_return > +#define atomic_dec_return atomic_dec_return > + > +#define atomic_fetch_inc_relaxed atomic_fetch_inc_relaxed > +#define atomic_fetch_dec_relaxed atomic_fetch_dec_relaxed > +#define atomic_fetch_inc atomic_fetch_inc > +#define atomic_fetch_dec atomic_fetch_dec > + > +#ifndef CONFIG_GENERIC_ATOMIC64 > +#define atomic64_inc_return_relaxed atomic64_inc_return_relaxed > +#define atomic64_dec_return_relaxed atomic64_dec_return_relaxed > +#define atomic64_inc_return atomic64_inc_return > +#define atomic64_dec_return atomic64_dec_return > + > +#define atomic64_fetch_inc_relaxed atomic64_fetch_inc_relaxed > +#define atomic64_fetch_dec_relaxed atomic64_fetch_dec_relaxed > +#define atomic64_fetch_inc atomic64_fetch_inc > +#define atomic64_fetch_dec atomic64_fetch_dec > +#endif > + > #undef ATOMIC_OPS > #undef ATOMIC_OP > #undef ATOMIC_FETCH_OP > #undef ATOMIC_OP_RETURN > > -#define ATOMIC_OP(op, func_op, comp_op, I, prefix) \ > -static __always_inline bool atomic##prefix##_##op(atomic##prefix##_t *v) \ > -{ \ > - return atomic##prefix##_##func_op##_return(v) comp_op I; \ > +#define ATOMIC_OP(op, func_op, comp_op, I, prefix) \ > +static __always_inline \ > +bool atomic##prefix##_##op(atomic##prefix##_t *v) \ > +{ \ > + return atomic##prefix##_##func_op##_return(v) comp_op I; \ > } > > ATOMIC_OP(inc_and_test, inc, ==, 0, ) > @@ -238,19 +331,19 @@ ATOMIC_OP(dec_and_test, dec, ==, 0, 64) > > #undef ATOMIC_OP > > -/* This is required to provide a barrier on success. */ > +/* This is required to provide a full barrier on success. */ > static __always_inline int __atomic_add_unless(atomic_t *v, int a, int u) > { > int prev, rc; > > __asm__ __volatile__ ( > - "0:\n\t" > - "lr.w.aqrl %[p], %[c]\n\t" > - "beq %[p], %[u], 1f\n\t" > - "add %[rc], %[p], %[a]\n\t" > - "sc.w.aqrl %[rc], %[rc], %[c]\n\t" > - "bnez %[rc], 0b\n\t" > - "1:" > + "0: lr.w %[p], %[c]\n" > + " beq %[p], %[u], 1f\n" > + " add %[rc], %[p], %[a]\n" > + " sc.w.rl %[rc], %[rc], %[c]\n" > + " bnez %[rc], 0b\n" > + " fence rw, rw\n" > + "1:\n" > : [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter) > : [a]"r" (a), [u]"r" (u) > : "memory"); > @@ -263,13 +356,13 @@ static __always_inline long __atomic64_add_unless(atomic64_t *v, long a, long u) > long prev, rc; > > __asm__ __volatile__ ( > - "0:\n\t" > - "lr.d.aqrl %[p], %[c]\n\t" > - "beq %[p], %[u], 1f\n\t" > - "add %[rc], %[p], %[a]\n\t" > - "sc.d.aqrl %[rc], %[rc], %[c]\n\t" > - "bnez %[rc], 0b\n\t" > - "1:" > + "0: lr.d %[p], %[c]\n" > + " beq %[p], %[u], 1f\n" > + " add %[rc], %[p], %[a]\n" > + " sc.d.rl %[rc], %[rc], %[c]\n" > + " bnez %[rc], 0b\n" > + " fence rw, rw\n" > + "1:\n" > : [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter) > : [a]"r" (a), [u]"r" (u) > : "memory"); > @@ -300,37 +393,63 @@ static __always_inline long atomic64_inc_not_zero(atomic64_t *v) > > /* > * atomic_{cmp,}xchg is required to have exactly the same ordering semantics as > - * {cmp,}xchg and the operations that return, so they need a barrier. > - */ > -/* > - * FIXME: atomic_cmpxchg_{acquire,release,relaxed} are all implemented by > - * assigning the same barrier to both the LR and SC operations, but that might > - * not make any sense. We're waiting on a memory model specification to > - * determine exactly what the right thing to do is here. > + * {cmp,}xchg and the operations that return, so they need a full barrier. > */ > -#define ATOMIC_OP(c_t, prefix, c_or, size, asm_or) \ > -static __always_inline c_t atomic##prefix##_cmpxchg##c_or(atomic##prefix##_t *v, c_t o, c_t n) \ > -{ \ > - return __cmpxchg(&(v->counter), o, n, size, asm_or, asm_or); \ > -} \ > -static __always_inline c_t atomic##prefix##_xchg##c_or(atomic##prefix##_t *v, c_t n) \ > -{ \ > - return __xchg(n, &(v->counter), size, asm_or); \ > +#define ATOMIC_OP(c_t, prefix, size) \ > +static __always_inline \ > +c_t atomic##prefix##_xchg_relaxed(atomic##prefix##_t *v, c_t n) \ > +{ \ > + return __xchg_relaxed(&(v->counter), n, size); \ > +} \ > +static __always_inline \ > +c_t atomic##prefix##_xchg_acquire(atomic##prefix##_t *v, c_t n) \ > +{ \ > + return __xchg_acquire(&(v->counter), n, size); \ > +} \ > +static __always_inline \ > +c_t atomic##prefix##_xchg_release(atomic##prefix##_t *v, c_t n) \ > +{ \ > + return __xchg_release(&(v->counter), n, size); \ > +} \ > +static __always_inline \ > +c_t atomic##prefix##_xchg(atomic##prefix##_t *v, c_t n) \ > +{ \ > + return __xchg(&(v->counter), n, size); \ > +} \ > +static __always_inline \ > +c_t atomic##prefix##_cmpxchg_relaxed(atomic##prefix##_t *v, \ > + c_t o, c_t n) \ > +{ \ > + return __cmpxchg_relaxed(&(v->counter), o, n, size); \ > +} \ > +static __always_inline \ > +c_t atomic##prefix##_cmpxchg_acquire(atomic##prefix##_t *v, \ > + c_t o, c_t n) \ > +{ \ > + return __cmpxchg_acquire(&(v->counter), o, n, size); \ > +} \ > +static __always_inline \ > +c_t atomic##prefix##_cmpxchg_release(atomic##prefix##_t *v, \ > + c_t o, c_t n) \ > +{ \ > + return __cmpxchg_release(&(v->counter), o, n, size); \ > +} \ > +static __always_inline \ > +c_t atomic##prefix##_cmpxchg(atomic##prefix##_t *v, c_t o, c_t n) \ > +{ \ > + return __cmpxchg(&(v->counter), o, n, size); \ > } > > #ifdef CONFIG_GENERIC_ATOMIC64 > -#define ATOMIC_OPS(c_or, asm_or) \ > - ATOMIC_OP( int, , c_or, 4, asm_or) > +#define ATOMIC_OPS() \ > + ATOMIC_OP( int, , 4) > #else > -#define ATOMIC_OPS(c_or, asm_or) \ > - ATOMIC_OP( int, , c_or, 4, asm_or) \ > - ATOMIC_OP(long, 64, c_or, 8, asm_or) > +#define ATOMIC_OPS() \ > + ATOMIC_OP( int, , 4) \ > + ATOMIC_OP(long, 64, 8) > #endif > > -ATOMIC_OPS( , .aqrl) > -ATOMIC_OPS(_acquire, .aq) > -ATOMIC_OPS(_release, .rl) > -ATOMIC_OPS(_relaxed, ) > +ATOMIC_OPS() > > #undef ATOMIC_OPS > #undef ATOMIC_OP > @@ -340,13 +459,13 @@ static __always_inline int atomic_sub_if_positive(atomic_t *v, int offset) > int prev, rc; > > __asm__ __volatile__ ( > - "0:\n\t" > - "lr.w.aqrl %[p], %[c]\n\t" > - "sub %[rc], %[p], %[o]\n\t" > - "bltz %[rc], 1f\n\t" > - "sc.w.aqrl %[rc], %[rc], %[c]\n\t" > - "bnez %[rc], 0b\n\t" > - "1:" > + "0: lr.w %[p], %[c]\n" > + " sub %[rc], %[p], %[o]\n" > + " bltz %[rc], 1f\n" > + " sc.w.rl %[rc], %[rc], %[c]\n" > + " bnez %[rc], 0b\n" > + " fence rw, rw\n" > + "1:\n" > : [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter) > : [o]"r" (offset) > : "memory"); > @@ -361,13 +480,13 @@ static __always_inline long atomic64_sub_if_positive(atomic64_t *v, int offset) > long prev, rc; > > __asm__ __volatile__ ( > - "0:\n\t" > - "lr.d.aqrl %[p], %[c]\n\t" > - "sub %[rc], %[p], %[o]\n\t" > - "bltz %[rc], 1f\n\t" > - "sc.d.aqrl %[rc], %[rc], %[c]\n\t" > - "bnez %[rc], 0b\n\t" > - "1:" > + "0: lr.d %[p], %[c]\n" > + " sub %[rc], %[p], %[o]\n" > + " bltz %[rc], 1f\n" > + " sc.d.rl %[rc], %[rc], %[c]\n" > + " bnez %[rc], 0b\n" > + " fence rw, rw\n" > + "1:\n" > : [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter) > : [o]"r" (offset) > : "memory"); > diff --git a/arch/riscv/include/asm/cmpxchg.h b/arch/riscv/include/asm/cmpxchg.h > index db249dbc7b976..c12833f7b6bd1 100644 > --- a/arch/riscv/include/asm/cmpxchg.h > +++ b/arch/riscv/include/asm/cmpxchg.h > @@ -17,45 +17,153 @@ > #include > > #include > +#include > > -#define __xchg(new, ptr, size, asm_or) \ > -({ \ > - __typeof__(ptr) __ptr = (ptr); \ > - __typeof__(new) __new = (new); \ > - __typeof__(*(ptr)) __ret; \ > - switch (size) { \ > - case 4: \ > - __asm__ __volatile__ ( \ > - "amoswap.w" #asm_or " %0, %2, %1" \ > - : "=r" (__ret), "+A" (*__ptr) \ > - : "r" (__new) \ > - : "memory"); \ > - break; \ > - case 8: \ > - __asm__ __volatile__ ( \ > - "amoswap.d" #asm_or " %0, %2, %1" \ > - : "=r" (__ret), "+A" (*__ptr) \ > - : "r" (__new) \ > - : "memory"); \ > - break; \ > - default: \ > - BUILD_BUG(); \ > - } \ > - __ret; \ > -}) > - > -#define xchg(ptr, x) (__xchg((x), (ptr), sizeof(*(ptr)), .aqrl)) > - > -#define xchg32(ptr, x) \ > -({ \ > - BUILD_BUG_ON(sizeof(*(ptr)) != 4); \ > - xchg((ptr), (x)); \ > -}) > - > -#define xchg64(ptr, x) \ > -({ \ > - BUILD_BUG_ON(sizeof(*(ptr)) != 8); \ > - xchg((ptr), (x)); \ > +#define __xchg_relaxed(ptr, new, size) \ > +({ \ > + __typeof__(ptr) __ptr = (ptr); \ > + __typeof__(new) __new = (new); \ > + __typeof__(*(ptr)) __ret; \ > + switch (size) { \ > + case 4: \ > + __asm__ __volatile__ ( \ > + " amoswap.w %0, %2, %1\n" \ > + : "=r" (__ret), "+A" (*__ptr) \ > + : "r" (__new) \ > + : "memory"); \ > + break; \ > + case 8: \ > + __asm__ __volatile__ ( \ > + " amoswap.d %0, %2, %1\n" \ > + : "=r" (__ret), "+A" (*__ptr) \ > + : "r" (__new) \ > + : "memory"); \ > + break; \ > + default: \ > + BUILD_BUG(); \ > + } \ > + __ret; \ > +}) > + > +#define xchg_relaxed(ptr, x) \ > +({ \ > + __typeof__(*(ptr)) _x_ = (x); \ > + (__typeof__(*(ptr))) __xchg_relaxed((ptr), \ > + _x_, sizeof(*(ptr))); \ > +}) > + > +#define __xchg_acquire(ptr, new, size) \ > +({ \ > + __typeof__(ptr) __ptr = (ptr); \ > + __typeof__(new) __new = (new); \ > + __typeof__(*(ptr)) __ret; \ > + switch (size) { \ > + case 4: \ > + __asm__ __volatile__ ( \ > + " amoswap.w %0, %2, %1\n" \ > + RISCV_ACQUIRE_BARRIER \ > + : "=r" (__ret), "+A" (*__ptr) \ > + : "r" (__new) \ > + : "memory"); \ > + break; \ > + case 8: \ > + __asm__ __volatile__ ( \ > + " amoswap.d %0, %2, %1\n" \ > + RISCV_ACQUIRE_BARRIER \ > + : "=r" (__ret), "+A" (*__ptr) \ > + : "r" (__new) \ > + : "memory"); \ > + break; \ > + default: \ > + BUILD_BUG(); \ > + } \ > + __ret; \ > +}) > + > +#define xchg_acquire(ptr, x) \ > +({ \ > + __typeof__(*(ptr)) _x_ = (x); \ > + (__typeof__(*(ptr))) __xchg_acquire((ptr), \ > + _x_, sizeof(*(ptr))); \ > +}) > + > +#define __xchg_release(ptr, new, size) \ > +({ \ > + __typeof__(ptr) __ptr = (ptr); \ > + __typeof__(new) __new = (new); \ > + __typeof__(*(ptr)) __ret; \ > + switch (size) { \ > + case 4: \ > + __asm__ __volatile__ ( \ > + RISCV_RELEASE_BARRIER \ > + " amoswap.w %0, %2, %1\n" \ > + : "=r" (__ret), "+A" (*__ptr) \ > + : "r" (__new) \ > + : "memory"); \ > + break; \ > + case 8: \ > + __asm__ __volatile__ ( \ > + RISCV_RELEASE_BARRIER \ > + " amoswap.d %0, %2, %1\n" \ > + : "=r" (__ret), "+A" (*__ptr) \ > + : "r" (__new) \ > + : "memory"); \ > + break; \ > + default: \ > + BUILD_BUG(); \ > + } \ > + __ret; \ > +}) > + > +#define xchg_release(ptr, x) \ > +({ \ > + __typeof__(*(ptr)) _x_ = (x); \ > + (__typeof__(*(ptr))) __xchg_release((ptr), \ > + _x_, sizeof(*(ptr))); \ > +}) > + > +#define __xchg(ptr, new, size) \ > +({ \ > + __typeof__(ptr) __ptr = (ptr); \ > + __typeof__(new) __new = (new); \ > + __typeof__(*(ptr)) __ret; \ > + switch (size) { \ > + case 4: \ > + __asm__ __volatile__ ( \ > + " amoswap.w.aqrl %0, %2, %1\n" \ > + : "=r" (__ret), "+A" (*__ptr) \ > + : "r" (__new) \ > + : "memory"); \ > + break; \ > + case 8: \ > + __asm__ __volatile__ ( \ > + " amoswap.d.aqrl %0, %2, %1\n" \ > + : "=r" (__ret), "+A" (*__ptr) \ > + : "r" (__new) \ > + : "memory"); \ > + break; \ > + default: \ > + BUILD_BUG(); \ > + } \ > + __ret; \ > +}) > + > +#define xchg(ptr, x) \ > +({ \ > + __typeof__(*(ptr)) _x_ = (x); \ > + (__typeof__(*(ptr))) __xchg((ptr), _x_, sizeof(*(ptr))); \ > +}) > + > +#define xchg32(ptr, x) \ > +({ \ > + BUILD_BUG_ON(sizeof(*(ptr)) != 4); \ > + xchg((ptr), (x)); \ > +}) > + > +#define xchg64(ptr, x) \ > +({ \ > + BUILD_BUG_ON(sizeof(*(ptr)) != 8); \ > + xchg((ptr), (x)); \ > }) > > /* > @@ -63,7 +171,51 @@ > * store NEW in MEM. Return the initial value in MEM. Success is > * indicated by comparing RETURN with OLD. > */ > -#define __cmpxchg(ptr, old, new, size, lrb, scb) \ > +#define __cmpxchg_relaxed(ptr, old, new, size) \ > +({ \ > + __typeof__(ptr) __ptr = (ptr); \ > + __typeof__(*(ptr)) __old = (old); \ > + __typeof__(*(ptr)) __new = (new); \ > + __typeof__(*(ptr)) __ret; \ > + register unsigned int __rc; \ > + switch (size) { \ > + case 4: \ > + __asm__ __volatile__ ( \ > + "0: lr.w %0, %2\n" \ > + " bne %0, %z3, 1f\n" \ > + " sc.w %1, %z4, %2\n" \ > + " bnez %1, 0b\n" \ > + "1:\n" \ > + : "=&r" (__ret), "=&r" (__rc), "+A" (*__ptr) \ > + : "rJ" (__old), "rJ" (__new) \ > + : "memory"); \ > + break; \ > + case 8: \ > + __asm__ __volatile__ ( \ > + "0: lr.d %0, %2\n" \ > + " bne %0, %z3, 1f\n" \ > + " sc.d %1, %z4, %2\n" \ > + " bnez %1, 0b\n" \ > + "1:\n" \ > + : "=&r" (__ret), "=&r" (__rc), "+A" (*__ptr) \ > + : "rJ" (__old), "rJ" (__new) \ > + : "memory"); \ > + break; \ > + default: \ > + BUILD_BUG(); \ > + } \ > + __ret; \ > +}) > + > +#define cmpxchg_relaxed(ptr, o, n) \ > +({ \ > + __typeof__(*(ptr)) _o_ = (o); \ > + __typeof__(*(ptr)) _n_ = (n); \ > + (__typeof__(*(ptr))) __cmpxchg_relaxed((ptr), \ > + _o_, _n_, sizeof(*(ptr))); \ > +}) > + > +#define __cmpxchg_acquire(ptr, old, new, size) \ > ({ \ > __typeof__(ptr) __ptr = (ptr); \ > __typeof__(*(ptr)) __old = (old); \ > @@ -73,24 +225,24 @@ > switch (size) { \ > case 4: \ > __asm__ __volatile__ ( \ > - "0:" \ > - "lr.w" #scb " %0, %2\n" \ > - "bne %0, %z3, 1f\n" \ > - "sc.w" #lrb " %1, %z4, %2\n" \ > - "bnez %1, 0b\n" \ > - "1:" \ > + "0: lr.w %0, %2\n" \ > + " bne %0, %z3, 1f\n" \ > + " sc.w %1, %z4, %2\n" \ > + " bnez %1, 0b\n" \ > + RISCV_ACQUIRE_BARRIER \ > + "1:\n" \ > : "=&r" (__ret), "=&r" (__rc), "+A" (*__ptr) \ > : "rJ" (__old), "rJ" (__new) \ > : "memory"); \ > break; \ > case 8: \ > __asm__ __volatile__ ( \ > - "0:" \ > - "lr.d" #scb " %0, %2\n" \ > - "bne %0, %z3, 1f\n" \ > - "sc.d" #lrb " %1, %z4, %2\n" \ > - "bnez %1, 0b\n" \ > - "1:" \ > + "0: lr.d %0, %2\n" \ > + " bne %0, %z3, 1f\n" \ > + " sc.d %1, %z4, %2\n" \ > + " bnez %1, 0b\n" \ > + RISCV_ACQUIRE_BARRIER \ > + "1:\n" \ > : "=&r" (__ret), "=&r" (__rc), "+A" (*__ptr) \ > : "rJ" (__old), "rJ" (__new) \ > : "memory"); \ > @@ -101,34 +253,131 @@ > __ret; \ > }) > > -#define cmpxchg(ptr, o, n) \ > - (__cmpxchg((ptr), (o), (n), sizeof(*(ptr)), .aqrl, .aqrl)) > +#define cmpxchg_acquire(ptr, o, n) \ > +({ \ > + __typeof__(*(ptr)) _o_ = (o); \ > + __typeof__(*(ptr)) _n_ = (n); \ > + (__typeof__(*(ptr))) __cmpxchg_acquire((ptr), \ > + _o_, _n_, sizeof(*(ptr))); \ > +}) > > -#define cmpxchg_local(ptr, o, n) \ > - (__cmpxchg((ptr), (o), (n), sizeof(*(ptr)), , )) > +#define __cmpxchg_release(ptr, old, new, size) \ > +({ \ > + __typeof__(ptr) __ptr = (ptr); \ > + __typeof__(*(ptr)) __old = (old); \ > + __typeof__(*(ptr)) __new = (new); \ > + __typeof__(*(ptr)) __ret; \ > + register unsigned int __rc; \ > + switch (size) { \ > + case 4: \ > + __asm__ __volatile__ ( \ > + RISCV_RELEASE_BARRIER \ > + "0: lr.w %0, %2\n" \ > + " bne %0, %z3, 1f\n" \ > + " sc.w %1, %z4, %2\n" \ > + " bnez %1, 0b\n" \ > + "1:\n" \ > + : "=&r" (__ret), "=&r" (__rc), "+A" (*__ptr) \ > + : "rJ" (__old), "rJ" (__new) \ > + : "memory"); \ > + break; \ > + case 8: \ > + __asm__ __volatile__ ( \ > + RISCV_RELEASE_BARRIER \ > + "0: lr.d %0, %2\n" \ > + " bne %0, %z3, 1f\n" \ > + " sc.d %1, %z4, %2\n" \ > + " bnez %1, 0b\n" \ > + "1:\n" \ > + : "=&r" (__ret), "=&r" (__rc), "+A" (*__ptr) \ > + : "rJ" (__old), "rJ" (__new) \ > + : "memory"); \ > + break; \ > + default: \ > + BUILD_BUG(); \ > + } \ > + __ret; \ > +}) > + > +#define cmpxchg_release(ptr, o, n) \ > +({ \ > + __typeof__(*(ptr)) _o_ = (o); \ > + __typeof__(*(ptr)) _n_ = (n); \ > + (__typeof__(*(ptr))) __cmpxchg_release((ptr), \ > + _o_, _n_, sizeof(*(ptr))); \ > +}) > + > +#define __cmpxchg(ptr, old, new, size) \ > +({ \ > + __typeof__(ptr) __ptr = (ptr); \ > + __typeof__(*(ptr)) __old = (old); \ > + __typeof__(*(ptr)) __new = (new); \ > + __typeof__(*(ptr)) __ret; \ > + register unsigned int __rc; \ > + switch (size) { \ > + case 4: \ > + __asm__ __volatile__ ( \ > + "0: lr.w %0, %2\n" \ > + " bne %0, %z3, 1f\n" \ > + " sc.w.rl %1, %z4, %2\n" \ > + " bnez %1, 0b\n" \ > + " fence rw, rw\n" \ > + "1:\n" \ > + : "=&r" (__ret), "=&r" (__rc), "+A" (*__ptr) \ > + : "rJ" (__old), "rJ" (__new) \ > + : "memory"); \ > + break; \ > + case 8: \ > + __asm__ __volatile__ ( \ > + "0: lr.d %0, %2\n" \ > + " bne %0, %z3, 1f\n" \ > + " sc.d.rl %1, %z4, %2\n" \ > + " bnez %1, 0b\n" \ > + " fence rw, rw\n" \ > + "1:\n" \ > + : "=&r" (__ret), "=&r" (__rc), "+A" (*__ptr) \ > + : "rJ" (__old), "rJ" (__new) \ > + : "memory"); \ > + break; \ > + default: \ > + BUILD_BUG(); \ > + } \ > + __ret; \ > +}) > > -#define cmpxchg32(ptr, o, n) \ > -({ \ > - BUILD_BUG_ON(sizeof(*(ptr)) != 4); \ > - cmpxchg((ptr), (o), (n)); \ > +#define cmpxchg(ptr, o, n) \ > +({ \ > + __typeof__(*(ptr)) _o_ = (o); \ > + __typeof__(*(ptr)) _n_ = (n); \ > + (__typeof__(*(ptr))) __cmpxchg((ptr), \ > + _o_, _n_, sizeof(*(ptr))); \ > }) > > -#define cmpxchg32_local(ptr, o, n) \ > -({ \ > - BUILD_BUG_ON(sizeof(*(ptr)) != 4); \ > - cmpxchg_local((ptr), (o), (n)); \ > +#define cmpxchg_local(ptr, o, n) \ > + (__cmpxchg_relaxed((ptr), (o), (n), sizeof(*(ptr)))) > + > +#define cmpxchg32(ptr, o, n) \ > +({ \ > + BUILD_BUG_ON(sizeof(*(ptr)) != 4); \ > + cmpxchg((ptr), (o), (n)); \ > }) > > -#define cmpxchg64(ptr, o, n) \ > -({ \ > - BUILD_BUG_ON(sizeof(*(ptr)) != 8); \ > - cmpxchg((ptr), (o), (n)); \ > +#define cmpxchg32_local(ptr, o, n) \ > +({ \ > + BUILD_BUG_ON(sizeof(*(ptr)) != 4); \ > + cmpxchg_relaxed((ptr), (o), (n)) \ > }) > > -#define cmpxchg64_local(ptr, o, n) \ > -({ \ > - BUILD_BUG_ON(sizeof(*(ptr)) != 8); \ > - cmpxchg_local((ptr), (o), (n)); \ > +#define cmpxchg64(ptr, o, n) \ > +({ \ > + BUILD_BUG_ON(sizeof(*(ptr)) != 8); \ > + cmpxchg((ptr), (o), (n)); \ > +}) > + > +#define cmpxchg64_local(ptr, o, n) \ > +({ \ > + BUILD_BUG_ON(sizeof(*(ptr)) != 8); \ > + cmpxchg_relaxed((ptr), (o), (n)); \ > }) > > #endif /* _ASM_RISCV_CMPXCHG_H */ From mboxrd@z Thu Jan 1 00:00:00 1970 From: palmer@sifive.com (Palmer Dabbelt) Date: Fri, 09 Mar 2018 09:56:21 -0800 (PST) Subject: [PATCH v2 2/2] riscv/atomic: Strengthen implementations with fences In-Reply-To: <1520597620-16650-1-git-send-email-parri.andrea@gmail.com> Message-ID: To: linux-riscv@lists.infradead.org List-Id: linux-riscv.lists.infradead.org On Fri, 09 Mar 2018 04:13:40 PST (-0800), parri.andrea at gmail.com wrote: > Atomics present the same issue with locking: release and acquire > variants need to be strengthened to meet the constraints defined > by the Linux-kernel memory consistency model [1]. > > Atomics present a further issue: implementations of atomics such > as atomic_cmpxchg() and atomic_add_unless() rely on LR/SC pairs, > which do not give full-ordering with .aqrl; for example, current > implementations allow the "lr-sc-aqrl-pair-vs-full-barrier" test > below to end up with the state indicated in the "exists" clause. > > In order to "synchronize" LKMM and RISC-V's implementation, this > commit strengthens the implementations of the atomics operations > by replacing .rl and .aq with the use of ("lightweigth") fences, > and by replacing .aqrl LR/SC pairs in sequences such as: > > 0: lr.w.aqrl %0, %addr > bne %0, %old, 1f > ... > sc.w.aqrl %1, %new, %addr > bnez %1, 0b > 1: > > with sequences of the form: > > 0: lr.w %0, %addr > bne %0, %old, 1f > ... > sc.w.rl %1, %new, %addr /* SC-release */ > bnez %1, 0b > fence rw, rw /* "full" fence */ > 1: > > following Daniel's suggestion. > > These modifications were validated with simulation of the RISC-V > memory consistency model. > > C lr-sc-aqrl-pair-vs-full-barrier > > {} > > P0(int *x, int *y, atomic_t *u) > { > int r0; > int r1; > > WRITE_ONCE(*x, 1); > r0 = atomic_cmpxchg(u, 0, 1); > r1 = READ_ONCE(*y); > } > > P1(int *x, int *y, atomic_t *v) > { > int r0; > int r1; > > WRITE_ONCE(*y, 1); > r0 = atomic_cmpxchg(v, 0, 1); > r1 = READ_ONCE(*x); > } > > exists (u=1 /\ v=1 /\ 0:r1=0 /\ 1:r1=0) > > [1] https://marc.info/?l=linux-kernel&m=151930201102853&w=2 > https://groups.google.com/a/groups.riscv.org/forum/#!topic/isa-dev/hKywNHBkAXM > https://marc.info/?l=linux-kernel&m=151633436614259&w=2 > > Suggested-by: Daniel Lustig > Signed-off-by: Andrea Parri > Cc: Palmer Dabbelt > Cc: Albert Ou > Cc: Daniel Lustig > Cc: Alan Stern > Cc: Will Deacon > Cc: Peter Zijlstra > Cc: Boqun Feng > Cc: Nicholas Piggin > Cc: David Howells > Cc: Jade Alglave > Cc: Luc Maranget > Cc: "Paul E. McKenney" > Cc: Akira Yokosawa > Cc: Ingo Molnar > Cc: Linus Torvalds > Cc: linux-riscv at lists.infradead.org > Cc: linux-kernel at vger.kernel.org > --- > arch/riscv/include/asm/atomic.h | 417 +++++++++++++++++++++++++-------------- > arch/riscv/include/asm/cmpxchg.h | 391 +++++++++++++++++++++++++++++------- > 2 files changed, 588 insertions(+), 220 deletions(-) > > diff --git a/arch/riscv/include/asm/atomic.h b/arch/riscv/include/asm/atomic.h > index e65d1cd89e28b..855115ace98c8 100644 > --- a/arch/riscv/include/asm/atomic.h > +++ b/arch/riscv/include/asm/atomic.h > @@ -24,6 +24,20 @@ > #include > > #define ATOMIC_INIT(i) { (i) } > + > +#define __atomic_op_acquire(op, args...) \ > +({ \ > + typeof(op##_relaxed(args)) __ret = op##_relaxed(args); \ > + __asm__ __volatile__(RISCV_ACQUIRE_BARRIER "" ::: "memory"); \ > + __ret; \ > +}) > + > +#define __atomic_op_release(op, args...) \ > +({ \ > + __asm__ __volatile__(RISCV_RELEASE_BARRIER "" ::: "memory"); \ > + op##_relaxed(args); \ > +}) > + > static __always_inline int atomic_read(const atomic_t *v) > { > return READ_ONCE(v->counter); > @@ -50,22 +64,23 @@ static __always_inline void atomic64_set(atomic64_t *v, long i) > * have the AQ or RL bits set. These don't return anything, so there's only > * one version to worry about. > */ > -#define ATOMIC_OP(op, asm_op, I, asm_type, c_type, prefix) \ > -static __always_inline void atomic##prefix##_##op(c_type i, atomic##prefix##_t *v) \ > -{ \ > - __asm__ __volatile__ ( \ > - "amo" #asm_op "." #asm_type " zero, %1, %0" \ > - : "+A" (v->counter) \ > - : "r" (I) \ > - : "memory"); \ > -} > +#define ATOMIC_OP(op, asm_op, I, asm_type, c_type, prefix) \ > +static __always_inline \ > +void atomic##prefix##_##op(c_type i, atomic##prefix##_t *v) \ > +{ \ > + __asm__ __volatile__ ( \ > + " amo" #asm_op "." #asm_type " zero, %1, %0" \ > + : "+A" (v->counter) \ > + : "r" (I) \ > + : "memory"); \ > +} \ Just to be sure: this is just a whitespace change, right? > #ifdef CONFIG_GENERIC_ATOMIC64 > -#define ATOMIC_OPS(op, asm_op, I) \ > +#define ATOMIC_OPS(op, asm_op, I) \ > ATOMIC_OP (op, asm_op, I, w, int, ) > #else > -#define ATOMIC_OPS(op, asm_op, I) \ > - ATOMIC_OP (op, asm_op, I, w, int, ) \ > +#define ATOMIC_OPS(op, asm_op, I) \ > + ATOMIC_OP (op, asm_op, I, w, int, ) \ > ATOMIC_OP (op, asm_op, I, d, long, 64) > #endif > > @@ -79,75 +94,115 @@ ATOMIC_OPS(xor, xor, i) > #undef ATOMIC_OPS > > /* > - * Atomic ops that have ordered, relaxed, acquire, and relese variants. > + * Atomic ops that have ordered, relaxed, acquire, and release variants. > * There's two flavors of these: the arithmatic ops have both fetch and return > * versions, while the logical ops only have fetch versions. > */ > -#define ATOMIC_FETCH_OP(op, asm_op, I, asm_or, c_or, asm_type, c_type, prefix) \ > -static __always_inline c_type atomic##prefix##_fetch_##op##c_or(c_type i, atomic##prefix##_t *v) \ > -{ \ > - register c_type ret; \ > - __asm__ __volatile__ ( \ > - "amo" #asm_op "." #asm_type #asm_or " %1, %2, %0" \ > - : "+A" (v->counter), "=r" (ret) \ > - : "r" (I) \ > - : "memory"); \ > - return ret; \ > +#define ATOMIC_FETCH_OP(op, asm_op, I, asm_type, c_type, prefix) \ > +static __always_inline \ > +c_type atomic##prefix##_fetch_##op##_relaxed(c_type i, \ > + atomic##prefix##_t *v) \ > +{ \ > + register c_type ret; \ > + __asm__ __volatile__ ( \ > + " amo" #asm_op "." #asm_type " %1, %2, %0" \ > + : "+A" (v->counter), "=r" (ret) \ > + : "r" (I) \ > + : "memory"); \ > + return ret; \ > +} \ > +static __always_inline \ > +c_type atomic##prefix##_fetch_##op(c_type i, atomic##prefix##_t *v) \ > +{ \ > + register c_type ret; \ > + __asm__ __volatile__ ( \ > + " amo" #asm_op "." #asm_type ".aqrl %1, %2, %0" \ > + : "+A" (v->counter), "=r" (ret) \ > + : "r" (I) \ > + : "memory"); \ > + return ret; \ > } > > -#define ATOMIC_OP_RETURN(op, asm_op, c_op, I, asm_or, c_or, asm_type, c_type, prefix) \ > -static __always_inline c_type atomic##prefix##_##op##_return##c_or(c_type i, atomic##prefix##_t *v) \ > -{ \ > - return atomic##prefix##_fetch_##op##c_or(i, v) c_op I; \ > +#define ATOMIC_OP_RETURN(op, asm_op, c_op, I, asm_type, c_type, prefix) \ > +static __always_inline \ > +c_type atomic##prefix##_##op##_return_relaxed(c_type i, \ > + atomic##prefix##_t *v) \ > +{ \ > + return atomic##prefix##_fetch_##op##_relaxed(i, v) c_op I; \ > +} \ > +static __always_inline \ > +c_type atomic##prefix##_##op##_return(c_type i, atomic##prefix##_t *v) \ > +{ \ > + return atomic##prefix##_fetch_##op(i, v) c_op I; \ > } > > #ifdef CONFIG_GENERIC_ATOMIC64 > -#define ATOMIC_OPS(op, asm_op, c_op, I, asm_or, c_or) \ > - ATOMIC_FETCH_OP (op, asm_op, I, asm_or, c_or, w, int, ) \ > - ATOMIC_OP_RETURN(op, asm_op, c_op, I, asm_or, c_or, w, int, ) > +#define ATOMIC_OPS(op, asm_op, c_op, I) \ > + ATOMIC_FETCH_OP( op, asm_op, I, w, int, ) \ > + ATOMIC_OP_RETURN(op, asm_op, c_op, I, w, int, ) > #else > -#define ATOMIC_OPS(op, asm_op, c_op, I, asm_or, c_or) \ > - ATOMIC_FETCH_OP (op, asm_op, I, asm_or, c_or, w, int, ) \ > - ATOMIC_OP_RETURN(op, asm_op, c_op, I, asm_or, c_or, w, int, ) \ > - ATOMIC_FETCH_OP (op, asm_op, I, asm_or, c_or, d, long, 64) \ > - ATOMIC_OP_RETURN(op, asm_op, c_op, I, asm_or, c_or, d, long, 64) > +#define ATOMIC_OPS(op, asm_op, c_op, I) \ > + ATOMIC_FETCH_OP( op, asm_op, I, w, int, ) \ > + ATOMIC_OP_RETURN(op, asm_op, c_op, I, w, int, ) \ > + ATOMIC_FETCH_OP( op, asm_op, I, d, long, 64) \ > + ATOMIC_OP_RETURN(op, asm_op, c_op, I, d, long, 64) > #endif > > -ATOMIC_OPS(add, add, +, i, , _relaxed) > -ATOMIC_OPS(add, add, +, i, .aq , _acquire) > -ATOMIC_OPS(add, add, +, i, .rl , _release) > -ATOMIC_OPS(add, add, +, i, .aqrl, ) > +ATOMIC_OPS(add, add, +, i) > +ATOMIC_OPS(sub, add, +, -i) Sorry, I must be missing something, but how do the acquire and release atomics get generated with this new code? > + > +#define atomic_add_return_relaxed atomic_add_return_relaxed > +#define atomic_sub_return_relaxed atomic_sub_return_relaxed > +#define atomic_add_return atomic_add_return > +#define atomic_sub_return atomic_sub_return > > -ATOMIC_OPS(sub, add, +, -i, , _relaxed) > -ATOMIC_OPS(sub, add, +, -i, .aq , _acquire) > -ATOMIC_OPS(sub, add, +, -i, .rl , _release) > -ATOMIC_OPS(sub, add, +, -i, .aqrl, ) > +#define atomic_fetch_add_relaxed atomic_fetch_add_relaxed > +#define atomic_fetch_sub_relaxed atomic_fetch_sub_relaxed > +#define atomic_fetch_add atomic_fetch_add > +#define atomic_fetch_sub atomic_fetch_sub > + > +#ifndef CONFIG_GENERIC_ATOMIC64 > +#define atomic64_add_return_relaxed atomic64_add_return_relaxed > +#define atomic64_sub_return_relaxed atomic64_sub_return_relaxed > +#define atomic64_add_return atomic64_add_return > +#define atomic64_sub_return atomic64_sub_return > + > +#define atomic64_fetch_add_relaxed atomic64_fetch_add_relaxed > +#define atomic64_fetch_sub_relaxed atomic64_fetch_sub_relaxed > +#define atomic64_fetch_add atomic64_fetch_add > +#define atomic64_fetch_sub atomic64_fetch_sub > +#endif > > #undef ATOMIC_OPS > > #ifdef CONFIG_GENERIC_ATOMIC64 > -#define ATOMIC_OPS(op, asm_op, I, asm_or, c_or) \ > - ATOMIC_FETCH_OP(op, asm_op, I, asm_or, c_or, w, int, ) > +#define ATOMIC_OPS(op, asm_op, I) \ > + ATOMIC_FETCH_OP(op, asm_op, I, w, int, ) > #else > -#define ATOMIC_OPS(op, asm_op, I, asm_or, c_or) \ > - ATOMIC_FETCH_OP(op, asm_op, I, asm_or, c_or, w, int, ) \ > - ATOMIC_FETCH_OP(op, asm_op, I, asm_or, c_or, d, long, 64) > +#define ATOMIC_OPS(op, asm_op, I) \ > + ATOMIC_FETCH_OP(op, asm_op, I, w, int, ) \ > + ATOMIC_FETCH_OP(op, asm_op, I, d, long, 64) > #endif > > -ATOMIC_OPS(and, and, i, , _relaxed) > -ATOMIC_OPS(and, and, i, .aq , _acquire) > -ATOMIC_OPS(and, and, i, .rl , _release) > -ATOMIC_OPS(and, and, i, .aqrl, ) > +ATOMIC_OPS(and, and, i) > +ATOMIC_OPS( or, or, i) > +ATOMIC_OPS(xor, xor, i) > > -ATOMIC_OPS( or, or, i, , _relaxed) > -ATOMIC_OPS( or, or, i, .aq , _acquire) > -ATOMIC_OPS( or, or, i, .rl , _release) > -ATOMIC_OPS( or, or, i, .aqrl, ) > +#define atomic_fetch_and_relaxed atomic_fetch_and_relaxed > +#define atomic_fetch_or_relaxed atomic_fetch_or_relaxed > +#define atomic_fetch_xor_relaxed atomic_fetch_xor_relaxed > +#define atomic_fetch_and atomic_fetch_and > +#define atomic_fetch_or atomic_fetch_or > +#define atomic_fetch_xor atomic_fetch_xor > > -ATOMIC_OPS(xor, xor, i, , _relaxed) > -ATOMIC_OPS(xor, xor, i, .aq , _acquire) > -ATOMIC_OPS(xor, xor, i, .rl , _release) > -ATOMIC_OPS(xor, xor, i, .aqrl, ) > +#ifndef CONFIG_GENERIC_ATOMIC64 > +#define atomic64_fetch_and_relaxed atomic64_fetch_and_relaxed > +#define atomic64_fetch_or_relaxed atomic64_fetch_or_relaxed > +#define atomic64_fetch_xor_relaxed atomic64_fetch_xor_relaxed > +#define atomic64_fetch_and atomic64_fetch_and > +#define atomic64_fetch_or atomic64_fetch_or > +#define atomic64_fetch_xor atomic64_fetch_xor > +#endif > > #undef ATOMIC_OPS > > @@ -157,22 +212,24 @@ ATOMIC_OPS(xor, xor, i, .aqrl, ) > /* > * The extra atomic operations that are constructed from one of the core > * AMO-based operations above (aside from sub, which is easier to fit above). > - * These are required to perform a barrier, but they're OK this way because > - * atomic_*_return is also required to perform a barrier. > + * These are required to perform a full barrier, but they're OK this way > + * because atomic_*_return is also required to perform a full barrier. > + * > */ > -#define ATOMIC_OP(op, func_op, comp_op, I, c_type, prefix) \ > -static __always_inline bool atomic##prefix##_##op(c_type i, atomic##prefix##_t *v) \ > -{ \ > - return atomic##prefix##_##func_op##_return(i, v) comp_op I; \ > +#define ATOMIC_OP(op, func_op, comp_op, I, c_type, prefix) \ > +static __always_inline \ > +bool atomic##prefix##_##op(c_type i, atomic##prefix##_t *v) \ > +{ \ > + return atomic##prefix##_##func_op##_return(i, v) comp_op I; \ > } > > #ifdef CONFIG_GENERIC_ATOMIC64 > -#define ATOMIC_OPS(op, func_op, comp_op, I) \ > - ATOMIC_OP (op, func_op, comp_op, I, int, ) > +#define ATOMIC_OPS(op, func_op, comp_op, I) \ > + ATOMIC_OP(op, func_op, comp_op, I, int, ) > #else > -#define ATOMIC_OPS(op, func_op, comp_op, I) \ > - ATOMIC_OP (op, func_op, comp_op, I, int, ) \ > - ATOMIC_OP (op, func_op, comp_op, I, long, 64) > +#define ATOMIC_OPS(op, func_op, comp_op, I) \ > + ATOMIC_OP(op, func_op, comp_op, I, int, ) \ > + ATOMIC_OP(op, func_op, comp_op, I, long, 64) > #endif > > ATOMIC_OPS(add_and_test, add, ==, 0) > @@ -182,51 +239,87 @@ ATOMIC_OPS(add_negative, add, <, 0) > #undef ATOMIC_OP > #undef ATOMIC_OPS > > -#define ATOMIC_OP(op, func_op, I, c_type, prefix) \ > -static __always_inline void atomic##prefix##_##op(atomic##prefix##_t *v) \ > -{ \ > - atomic##prefix##_##func_op(I, v); \ > +#define ATOMIC_OP(op, func_op, I, c_type, prefix) \ > +static __always_inline \ > +void atomic##prefix##_##op(atomic##prefix##_t *v) \ > +{ \ > + atomic##prefix##_##func_op(I, v); \ > } > > -#define ATOMIC_FETCH_OP(op, func_op, I, c_type, prefix) \ > -static __always_inline c_type atomic##prefix##_fetch_##op(atomic##prefix##_t *v) \ > -{ \ > - return atomic##prefix##_fetch_##func_op(I, v); \ > +#define ATOMIC_FETCH_OP(op, func_op, I, c_type, prefix) \ > +static __always_inline \ > +c_type atomic##prefix##_fetch_##op##_relaxed(atomic##prefix##_t *v) \ > +{ \ > + return atomic##prefix##_fetch_##func_op##_relaxed(I, v); \ > +} \ > +static __always_inline \ > +c_type atomic##prefix##_fetch_##op(atomic##prefix##_t *v) \ > +{ \ > + return atomic##prefix##_fetch_##func_op(I, v); \ > } > > -#define ATOMIC_OP_RETURN(op, asm_op, c_op, I, c_type, prefix) \ > -static __always_inline c_type atomic##prefix##_##op##_return(atomic##prefix##_t *v) \ > -{ \ > - return atomic##prefix##_fetch_##op(v) c_op I; \ > +#define ATOMIC_OP_RETURN(op, asm_op, c_op, I, c_type, prefix) \ > +static __always_inline \ > +c_type atomic##prefix##_##op##_return_relaxed(atomic##prefix##_t *v) \ > +{ \ > + return atomic##prefix##_fetch_##op##_relaxed(v) c_op I; \ > +} \ > +static __always_inline \ > +c_type atomic##prefix##_##op##_return(atomic##prefix##_t *v) \ > +{ \ > + return atomic##prefix##_fetch_##op(v) c_op I; \ > } > > #ifdef CONFIG_GENERIC_ATOMIC64 > -#define ATOMIC_OPS(op, asm_op, c_op, I) \ > - ATOMIC_OP (op, asm_op, I, int, ) \ > - ATOMIC_FETCH_OP (op, asm_op, I, int, ) \ > +#define ATOMIC_OPS(op, asm_op, c_op, I) \ > + ATOMIC_OP( op, asm_op, I, int, ) \ > + ATOMIC_FETCH_OP( op, asm_op, I, int, ) \ > ATOMIC_OP_RETURN(op, asm_op, c_op, I, int, ) > #else > -#define ATOMIC_OPS(op, asm_op, c_op, I) \ > - ATOMIC_OP (op, asm_op, I, int, ) \ > - ATOMIC_FETCH_OP (op, asm_op, I, int, ) \ > - ATOMIC_OP_RETURN(op, asm_op, c_op, I, int, ) \ > - ATOMIC_OP (op, asm_op, I, long, 64) \ > - ATOMIC_FETCH_OP (op, asm_op, I, long, 64) \ > +#define ATOMIC_OPS(op, asm_op, c_op, I) \ > + ATOMIC_OP( op, asm_op, I, int, ) \ > + ATOMIC_FETCH_OP( op, asm_op, I, int, ) \ > + ATOMIC_OP_RETURN(op, asm_op, c_op, I, int, ) \ > + ATOMIC_OP( op, asm_op, I, long, 64) \ > + ATOMIC_FETCH_OP( op, asm_op, I, long, 64) \ > ATOMIC_OP_RETURN(op, asm_op, c_op, I, long, 64) > #endif > > ATOMIC_OPS(inc, add, +, 1) > ATOMIC_OPS(dec, add, +, -1) > > +#define atomic_inc_return_relaxed atomic_inc_return_relaxed > +#define atomic_dec_return_relaxed atomic_dec_return_relaxed > +#define atomic_inc_return atomic_inc_return > +#define atomic_dec_return atomic_dec_return > + > +#define atomic_fetch_inc_relaxed atomic_fetch_inc_relaxed > +#define atomic_fetch_dec_relaxed atomic_fetch_dec_relaxed > +#define atomic_fetch_inc atomic_fetch_inc > +#define atomic_fetch_dec atomic_fetch_dec > + > +#ifndef CONFIG_GENERIC_ATOMIC64 > +#define atomic64_inc_return_relaxed atomic64_inc_return_relaxed > +#define atomic64_dec_return_relaxed atomic64_dec_return_relaxed > +#define atomic64_inc_return atomic64_inc_return > +#define atomic64_dec_return atomic64_dec_return > + > +#define atomic64_fetch_inc_relaxed atomic64_fetch_inc_relaxed > +#define atomic64_fetch_dec_relaxed atomic64_fetch_dec_relaxed > +#define atomic64_fetch_inc atomic64_fetch_inc > +#define atomic64_fetch_dec atomic64_fetch_dec > +#endif > + > #undef ATOMIC_OPS > #undef ATOMIC_OP > #undef ATOMIC_FETCH_OP > #undef ATOMIC_OP_RETURN > > -#define ATOMIC_OP(op, func_op, comp_op, I, prefix) \ > -static __always_inline bool atomic##prefix##_##op(atomic##prefix##_t *v) \ > -{ \ > - return atomic##prefix##_##func_op##_return(v) comp_op I; \ > +#define ATOMIC_OP(op, func_op, comp_op, I, prefix) \ > +static __always_inline \ > +bool atomic##prefix##_##op(atomic##prefix##_t *v) \ > +{ \ > + return atomic##prefix##_##func_op##_return(v) comp_op I; \ > } > > ATOMIC_OP(inc_and_test, inc, ==, 0, ) > @@ -238,19 +331,19 @@ ATOMIC_OP(dec_and_test, dec, ==, 0, 64) > > #undef ATOMIC_OP > > -/* This is required to provide a barrier on success. */ > +/* This is required to provide a full barrier on success. */ > static __always_inline int __atomic_add_unless(atomic_t *v, int a, int u) > { > int prev, rc; > > __asm__ __volatile__ ( > - "0:\n\t" > - "lr.w.aqrl %[p], %[c]\n\t" > - "beq %[p], %[u], 1f\n\t" > - "add %[rc], %[p], %[a]\n\t" > - "sc.w.aqrl %[rc], %[rc], %[c]\n\t" > - "bnez %[rc], 0b\n\t" > - "1:" > + "0: lr.w %[p], %[c]\n" > + " beq %[p], %[u], 1f\n" > + " add %[rc], %[p], %[a]\n" > + " sc.w.rl %[rc], %[rc], %[c]\n" > + " bnez %[rc], 0b\n" > + " fence rw, rw\n" > + "1:\n" > : [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter) > : [a]"r" (a), [u]"r" (u) > : "memory"); > @@ -263,13 +356,13 @@ static __always_inline long __atomic64_add_unless(atomic64_t *v, long a, long u) > long prev, rc; > > __asm__ __volatile__ ( > - "0:\n\t" > - "lr.d.aqrl %[p], %[c]\n\t" > - "beq %[p], %[u], 1f\n\t" > - "add %[rc], %[p], %[a]\n\t" > - "sc.d.aqrl %[rc], %[rc], %[c]\n\t" > - "bnez %[rc], 0b\n\t" > - "1:" > + "0: lr.d %[p], %[c]\n" > + " beq %[p], %[u], 1f\n" > + " add %[rc], %[p], %[a]\n" > + " sc.d.rl %[rc], %[rc], %[c]\n" > + " bnez %[rc], 0b\n" > + " fence rw, rw\n" > + "1:\n" > : [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter) > : [a]"r" (a), [u]"r" (u) > : "memory"); > @@ -300,37 +393,63 @@ static __always_inline long atomic64_inc_not_zero(atomic64_t *v) > > /* > * atomic_{cmp,}xchg is required to have exactly the same ordering semantics as > - * {cmp,}xchg and the operations that return, so they need a barrier. > - */ > -/* > - * FIXME: atomic_cmpxchg_{acquire,release,relaxed} are all implemented by > - * assigning the same barrier to both the LR and SC operations, but that might > - * not make any sense. We're waiting on a memory model specification to > - * determine exactly what the right thing to do is here. > + * {cmp,}xchg and the operations that return, so they need a full barrier. > */ > -#define ATOMIC_OP(c_t, prefix, c_or, size, asm_or) \ > -static __always_inline c_t atomic##prefix##_cmpxchg##c_or(atomic##prefix##_t *v, c_t o, c_t n) \ > -{ \ > - return __cmpxchg(&(v->counter), o, n, size, asm_or, asm_or); \ > -} \ > -static __always_inline c_t atomic##prefix##_xchg##c_or(atomic##prefix##_t *v, c_t n) \ > -{ \ > - return __xchg(n, &(v->counter), size, asm_or); \ > +#define ATOMIC_OP(c_t, prefix, size) \ > +static __always_inline \ > +c_t atomic##prefix##_xchg_relaxed(atomic##prefix##_t *v, c_t n) \ > +{ \ > + return __xchg_relaxed(&(v->counter), n, size); \ > +} \ > +static __always_inline \ > +c_t atomic##prefix##_xchg_acquire(atomic##prefix##_t *v, c_t n) \ > +{ \ > + return __xchg_acquire(&(v->counter), n, size); \ > +} \ > +static __always_inline \ > +c_t atomic##prefix##_xchg_release(atomic##prefix##_t *v, c_t n) \ > +{ \ > + return __xchg_release(&(v->counter), n, size); \ > +} \ > +static __always_inline \ > +c_t atomic##prefix##_xchg(atomic##prefix##_t *v, c_t n) \ > +{ \ > + return __xchg(&(v->counter), n, size); \ > +} \ > +static __always_inline \ > +c_t atomic##prefix##_cmpxchg_relaxed(atomic##prefix##_t *v, \ > + c_t o, c_t n) \ > +{ \ > + return __cmpxchg_relaxed(&(v->counter), o, n, size); \ > +} \ > +static __always_inline \ > +c_t atomic##prefix##_cmpxchg_acquire(atomic##prefix##_t *v, \ > + c_t o, c_t n) \ > +{ \ > + return __cmpxchg_acquire(&(v->counter), o, n, size); \ > +} \ > +static __always_inline \ > +c_t atomic##prefix##_cmpxchg_release(atomic##prefix##_t *v, \ > + c_t o, c_t n) \ > +{ \ > + return __cmpxchg_release(&(v->counter), o, n, size); \ > +} \ > +static __always_inline \ > +c_t atomic##prefix##_cmpxchg(atomic##prefix##_t *v, c_t o, c_t n) \ > +{ \ > + return __cmpxchg(&(v->counter), o, n, size); \ > } > > #ifdef CONFIG_GENERIC_ATOMIC64 > -#define ATOMIC_OPS(c_or, asm_or) \ > - ATOMIC_OP( int, , c_or, 4, asm_or) > +#define ATOMIC_OPS() \ > + ATOMIC_OP( int, , 4) > #else > -#define ATOMIC_OPS(c_or, asm_or) \ > - ATOMIC_OP( int, , c_or, 4, asm_or) \ > - ATOMIC_OP(long, 64, c_or, 8, asm_or) > +#define ATOMIC_OPS() \ > + ATOMIC_OP( int, , 4) \ > + ATOMIC_OP(long, 64, 8) > #endif > > -ATOMIC_OPS( , .aqrl) > -ATOMIC_OPS(_acquire, .aq) > -ATOMIC_OPS(_release, .rl) > -ATOMIC_OPS(_relaxed, ) > +ATOMIC_OPS() > > #undef ATOMIC_OPS > #undef ATOMIC_OP > @@ -340,13 +459,13 @@ static __always_inline int atomic_sub_if_positive(atomic_t *v, int offset) > int prev, rc; > > __asm__ __volatile__ ( > - "0:\n\t" > - "lr.w.aqrl %[p], %[c]\n\t" > - "sub %[rc], %[p], %[o]\n\t" > - "bltz %[rc], 1f\n\t" > - "sc.w.aqrl %[rc], %[rc], %[c]\n\t" > - "bnez %[rc], 0b\n\t" > - "1:" > + "0: lr.w %[p], %[c]\n" > + " sub %[rc], %[p], %[o]\n" > + " bltz %[rc], 1f\n" > + " sc.w.rl %[rc], %[rc], %[c]\n" > + " bnez %[rc], 0b\n" > + " fence rw, rw\n" > + "1:\n" > : [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter) > : [o]"r" (offset) > : "memory"); > @@ -361,13 +480,13 @@ static __always_inline long atomic64_sub_if_positive(atomic64_t *v, int offset) > long prev, rc; > > __asm__ __volatile__ ( > - "0:\n\t" > - "lr.d.aqrl %[p], %[c]\n\t" > - "sub %[rc], %[p], %[o]\n\t" > - "bltz %[rc], 1f\n\t" > - "sc.d.aqrl %[rc], %[rc], %[c]\n\t" > - "bnez %[rc], 0b\n\t" > - "1:" > + "0: lr.d %[p], %[c]\n" > + " sub %[rc], %[p], %[o]\n" > + " bltz %[rc], 1f\n" > + " sc.d.rl %[rc], %[rc], %[c]\n" > + " bnez %[rc], 0b\n" > + " fence rw, rw\n" > + "1:\n" > : [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter) > : [o]"r" (offset) > : "memory"); > diff --git a/arch/riscv/include/asm/cmpxchg.h b/arch/riscv/include/asm/cmpxchg.h > index db249dbc7b976..c12833f7b6bd1 100644 > --- a/arch/riscv/include/asm/cmpxchg.h > +++ b/arch/riscv/include/asm/cmpxchg.h > @@ -17,45 +17,153 @@ > #include > > #include > +#include > > -#define __xchg(new, ptr, size, asm_or) \ > -({ \ > - __typeof__(ptr) __ptr = (ptr); \ > - __typeof__(new) __new = (new); \ > - __typeof__(*(ptr)) __ret; \ > - switch (size) { \ > - case 4: \ > - __asm__ __volatile__ ( \ > - "amoswap.w" #asm_or " %0, %2, %1" \ > - : "=r" (__ret), "+A" (*__ptr) \ > - : "r" (__new) \ > - : "memory"); \ > - break; \ > - case 8: \ > - __asm__ __volatile__ ( \ > - "amoswap.d" #asm_or " %0, %2, %1" \ > - : "=r" (__ret), "+A" (*__ptr) \ > - : "r" (__new) \ > - : "memory"); \ > - break; \ > - default: \ > - BUILD_BUG(); \ > - } \ > - __ret; \ > -}) > - > -#define xchg(ptr, x) (__xchg((x), (ptr), sizeof(*(ptr)), .aqrl)) > - > -#define xchg32(ptr, x) \ > -({ \ > - BUILD_BUG_ON(sizeof(*(ptr)) != 4); \ > - xchg((ptr), (x)); \ > -}) > - > -#define xchg64(ptr, x) \ > -({ \ > - BUILD_BUG_ON(sizeof(*(ptr)) != 8); \ > - xchg((ptr), (x)); \ > +#define __xchg_relaxed(ptr, new, size) \ > +({ \ > + __typeof__(ptr) __ptr = (ptr); \ > + __typeof__(new) __new = (new); \ > + __typeof__(*(ptr)) __ret; \ > + switch (size) { \ > + case 4: \ > + __asm__ __volatile__ ( \ > + " amoswap.w %0, %2, %1\n" \ > + : "=r" (__ret), "+A" (*__ptr) \ > + : "r" (__new) \ > + : "memory"); \ > + break; \ > + case 8: \ > + __asm__ __volatile__ ( \ > + " amoswap.d %0, %2, %1\n" \ > + : "=r" (__ret), "+A" (*__ptr) \ > + : "r" (__new) \ > + : "memory"); \ > + break; \ > + default: \ > + BUILD_BUG(); \ > + } \ > + __ret; \ > +}) > + > +#define xchg_relaxed(ptr, x) \ > +({ \ > + __typeof__(*(ptr)) _x_ = (x); \ > + (__typeof__(*(ptr))) __xchg_relaxed((ptr), \ > + _x_, sizeof(*(ptr))); \ > +}) > + > +#define __xchg_acquire(ptr, new, size) \ > +({ \ > + __typeof__(ptr) __ptr = (ptr); \ > + __typeof__(new) __new = (new); \ > + __typeof__(*(ptr)) __ret; \ > + switch (size) { \ > + case 4: \ > + __asm__ __volatile__ ( \ > + " amoswap.w %0, %2, %1\n" \ > + RISCV_ACQUIRE_BARRIER \ > + : "=r" (__ret), "+A" (*__ptr) \ > + : "r" (__new) \ > + : "memory"); \ > + break; \ > + case 8: \ > + __asm__ __volatile__ ( \ > + " amoswap.d %0, %2, %1\n" \ > + RISCV_ACQUIRE_BARRIER \ > + : "=r" (__ret), "+A" (*__ptr) \ > + : "r" (__new) \ > + : "memory"); \ > + break; \ > + default: \ > + BUILD_BUG(); \ > + } \ > + __ret; \ > +}) > + > +#define xchg_acquire(ptr, x) \ > +({ \ > + __typeof__(*(ptr)) _x_ = (x); \ > + (__typeof__(*(ptr))) __xchg_acquire((ptr), \ > + _x_, sizeof(*(ptr))); \ > +}) > + > +#define __xchg_release(ptr, new, size) \ > +({ \ > + __typeof__(ptr) __ptr = (ptr); \ > + __typeof__(new) __new = (new); \ > + __typeof__(*(ptr)) __ret; \ > + switch (size) { \ > + case 4: \ > + __asm__ __volatile__ ( \ > + RISCV_RELEASE_BARRIER \ > + " amoswap.w %0, %2, %1\n" \ > + : "=r" (__ret), "+A" (*__ptr) \ > + : "r" (__new) \ > + : "memory"); \ > + break; \ > + case 8: \ > + __asm__ __volatile__ ( \ > + RISCV_RELEASE_BARRIER \ > + " amoswap.d %0, %2, %1\n" \ > + : "=r" (__ret), "+A" (*__ptr) \ > + : "r" (__new) \ > + : "memory"); \ > + break; \ > + default: \ > + BUILD_BUG(); \ > + } \ > + __ret; \ > +}) > + > +#define xchg_release(ptr, x) \ > +({ \ > + __typeof__(*(ptr)) _x_ = (x); \ > + (__typeof__(*(ptr))) __xchg_release((ptr), \ > + _x_, sizeof(*(ptr))); \ > +}) > + > +#define __xchg(ptr, new, size) \ > +({ \ > + __typeof__(ptr) __ptr = (ptr); \ > + __typeof__(new) __new = (new); \ > + __typeof__(*(ptr)) __ret; \ > + switch (size) { \ > + case 4: \ > + __asm__ __volatile__ ( \ > + " amoswap.w.aqrl %0, %2, %1\n" \ > + : "=r" (__ret), "+A" (*__ptr) \ > + : "r" (__new) \ > + : "memory"); \ > + break; \ > + case 8: \ > + __asm__ __volatile__ ( \ > + " amoswap.d.aqrl %0, %2, %1\n" \ > + : "=r" (__ret), "+A" (*__ptr) \ > + : "r" (__new) \ > + : "memory"); \ > + break; \ > + default: \ > + BUILD_BUG(); \ > + } \ > + __ret; \ > +}) > + > +#define xchg(ptr, x) \ > +({ \ > + __typeof__(*(ptr)) _x_ = (x); \ > + (__typeof__(*(ptr))) __xchg((ptr), _x_, sizeof(*(ptr))); \ > +}) > + > +#define xchg32(ptr, x) \ > +({ \ > + BUILD_BUG_ON(sizeof(*(ptr)) != 4); \ > + xchg((ptr), (x)); \ > +}) > + > +#define xchg64(ptr, x) \ > +({ \ > + BUILD_BUG_ON(sizeof(*(ptr)) != 8); \ > + xchg((ptr), (x)); \ > }) > > /* > @@ -63,7 +171,51 @@ > * store NEW in MEM. Return the initial value in MEM. Success is > * indicated by comparing RETURN with OLD. > */ > -#define __cmpxchg(ptr, old, new, size, lrb, scb) \ > +#define __cmpxchg_relaxed(ptr, old, new, size) \ > +({ \ > + __typeof__(ptr) __ptr = (ptr); \ > + __typeof__(*(ptr)) __old = (old); \ > + __typeof__(*(ptr)) __new = (new); \ > + __typeof__(*(ptr)) __ret; \ > + register unsigned int __rc; \ > + switch (size) { \ > + case 4: \ > + __asm__ __volatile__ ( \ > + "0: lr.w %0, %2\n" \ > + " bne %0, %z3, 1f\n" \ > + " sc.w %1, %z4, %2\n" \ > + " bnez %1, 0b\n" \ > + "1:\n" \ > + : "=&r" (__ret), "=&r" (__rc), "+A" (*__ptr) \ > + : "rJ" (__old), "rJ" (__new) \ > + : "memory"); \ > + break; \ > + case 8: \ > + __asm__ __volatile__ ( \ > + "0: lr.d %0, %2\n" \ > + " bne %0, %z3, 1f\n" \ > + " sc.d %1, %z4, %2\n" \ > + " bnez %1, 0b\n" \ > + "1:\n" \ > + : "=&r" (__ret), "=&r" (__rc), "+A" (*__ptr) \ > + : "rJ" (__old), "rJ" (__new) \ > + : "memory"); \ > + break; \ > + default: \ > + BUILD_BUG(); \ > + } \ > + __ret; \ > +}) > + > +#define cmpxchg_relaxed(ptr, o, n) \ > +({ \ > + __typeof__(*(ptr)) _o_ = (o); \ > + __typeof__(*(ptr)) _n_ = (n); \ > + (__typeof__(*(ptr))) __cmpxchg_relaxed((ptr), \ > + _o_, _n_, sizeof(*(ptr))); \ > +}) > + > +#define __cmpxchg_acquire(ptr, old, new, size) \ > ({ \ > __typeof__(ptr) __ptr = (ptr); \ > __typeof__(*(ptr)) __old = (old); \ > @@ -73,24 +225,24 @@ > switch (size) { \ > case 4: \ > __asm__ __volatile__ ( \ > - "0:" \ > - "lr.w" #scb " %0, %2\n" \ > - "bne %0, %z3, 1f\n" \ > - "sc.w" #lrb " %1, %z4, %2\n" \ > - "bnez %1, 0b\n" \ > - "1:" \ > + "0: lr.w %0, %2\n" \ > + " bne %0, %z3, 1f\n" \ > + " sc.w %1, %z4, %2\n" \ > + " bnez %1, 0b\n" \ > + RISCV_ACQUIRE_BARRIER \ > + "1:\n" \ > : "=&r" (__ret), "=&r" (__rc), "+A" (*__ptr) \ > : "rJ" (__old), "rJ" (__new) \ > : "memory"); \ > break; \ > case 8: \ > __asm__ __volatile__ ( \ > - "0:" \ > - "lr.d" #scb " %0, %2\n" \ > - "bne %0, %z3, 1f\n" \ > - "sc.d" #lrb " %1, %z4, %2\n" \ > - "bnez %1, 0b\n" \ > - "1:" \ > + "0: lr.d %0, %2\n" \ > + " bne %0, %z3, 1f\n" \ > + " sc.d %1, %z4, %2\n" \ > + " bnez %1, 0b\n" \ > + RISCV_ACQUIRE_BARRIER \ > + "1:\n" \ > : "=&r" (__ret), "=&r" (__rc), "+A" (*__ptr) \ > : "rJ" (__old), "rJ" (__new) \ > : "memory"); \ > @@ -101,34 +253,131 @@ > __ret; \ > }) > > -#define cmpxchg(ptr, o, n) \ > - (__cmpxchg((ptr), (o), (n), sizeof(*(ptr)), .aqrl, .aqrl)) > +#define cmpxchg_acquire(ptr, o, n) \ > +({ \ > + __typeof__(*(ptr)) _o_ = (o); \ > + __typeof__(*(ptr)) _n_ = (n); \ > + (__typeof__(*(ptr))) __cmpxchg_acquire((ptr), \ > + _o_, _n_, sizeof(*(ptr))); \ > +}) > > -#define cmpxchg_local(ptr, o, n) \ > - (__cmpxchg((ptr), (o), (n), sizeof(*(ptr)), , )) > +#define __cmpxchg_release(ptr, old, new, size) \ > +({ \ > + __typeof__(ptr) __ptr = (ptr); \ > + __typeof__(*(ptr)) __old = (old); \ > + __typeof__(*(ptr)) __new = (new); \ > + __typeof__(*(ptr)) __ret; \ > + register unsigned int __rc; \ > + switch (size) { \ > + case 4: \ > + __asm__ __volatile__ ( \ > + RISCV_RELEASE_BARRIER \ > + "0: lr.w %0, %2\n" \ > + " bne %0, %z3, 1f\n" \ > + " sc.w %1, %z4, %2\n" \ > + " bnez %1, 0b\n" \ > + "1:\n" \ > + : "=&r" (__ret), "=&r" (__rc), "+A" (*__ptr) \ > + : "rJ" (__old), "rJ" (__new) \ > + : "memory"); \ > + break; \ > + case 8: \ > + __asm__ __volatile__ ( \ > + RISCV_RELEASE_BARRIER \ > + "0: lr.d %0, %2\n" \ > + " bne %0, %z3, 1f\n" \ > + " sc.d %1, %z4, %2\n" \ > + " bnez %1, 0b\n" \ > + "1:\n" \ > + : "=&r" (__ret), "=&r" (__rc), "+A" (*__ptr) \ > + : "rJ" (__old), "rJ" (__new) \ > + : "memory"); \ > + break; \ > + default: \ > + BUILD_BUG(); \ > + } \ > + __ret; \ > +}) > + > +#define cmpxchg_release(ptr, o, n) \ > +({ \ > + __typeof__(*(ptr)) _o_ = (o); \ > + __typeof__(*(ptr)) _n_ = (n); \ > + (__typeof__(*(ptr))) __cmpxchg_release((ptr), \ > + _o_, _n_, sizeof(*(ptr))); \ > +}) > + > +#define __cmpxchg(ptr, old, new, size) \ > +({ \ > + __typeof__(ptr) __ptr = (ptr); \ > + __typeof__(*(ptr)) __old = (old); \ > + __typeof__(*(ptr)) __new = (new); \ > + __typeof__(*(ptr)) __ret; \ > + register unsigned int __rc; \ > + switch (size) { \ > + case 4: \ > + __asm__ __volatile__ ( \ > + "0: lr.w %0, %2\n" \ > + " bne %0, %z3, 1f\n" \ > + " sc.w.rl %1, %z4, %2\n" \ > + " bnez %1, 0b\n" \ > + " fence rw, rw\n" \ > + "1:\n" \ > + : "=&r" (__ret), "=&r" (__rc), "+A" (*__ptr) \ > + : "rJ" (__old), "rJ" (__new) \ > + : "memory"); \ > + break; \ > + case 8: \ > + __asm__ __volatile__ ( \ > + "0: lr.d %0, %2\n" \ > + " bne %0, %z3, 1f\n" \ > + " sc.d.rl %1, %z4, %2\n" \ > + " bnez %1, 0b\n" \ > + " fence rw, rw\n" \ > + "1:\n" \ > + : "=&r" (__ret), "=&r" (__rc), "+A" (*__ptr) \ > + : "rJ" (__old), "rJ" (__new) \ > + : "memory"); \ > + break; \ > + default: \ > + BUILD_BUG(); \ > + } \ > + __ret; \ > +}) > > -#define cmpxchg32(ptr, o, n) \ > -({ \ > - BUILD_BUG_ON(sizeof(*(ptr)) != 4); \ > - cmpxchg((ptr), (o), (n)); \ > +#define cmpxchg(ptr, o, n) \ > +({ \ > + __typeof__(*(ptr)) _o_ = (o); \ > + __typeof__(*(ptr)) _n_ = (n); \ > + (__typeof__(*(ptr))) __cmpxchg((ptr), \ > + _o_, _n_, sizeof(*(ptr))); \ > }) > > -#define cmpxchg32_local(ptr, o, n) \ > -({ \ > - BUILD_BUG_ON(sizeof(*(ptr)) != 4); \ > - cmpxchg_local((ptr), (o), (n)); \ > +#define cmpxchg_local(ptr, o, n) \ > + (__cmpxchg_relaxed((ptr), (o), (n), sizeof(*(ptr)))) > + > +#define cmpxchg32(ptr, o, n) \ > +({ \ > + BUILD_BUG_ON(sizeof(*(ptr)) != 4); \ > + cmpxchg((ptr), (o), (n)); \ > }) > > -#define cmpxchg64(ptr, o, n) \ > -({ \ > - BUILD_BUG_ON(sizeof(*(ptr)) != 8); \ > - cmpxchg((ptr), (o), (n)); \ > +#define cmpxchg32_local(ptr, o, n) \ > +({ \ > + BUILD_BUG_ON(sizeof(*(ptr)) != 4); \ > + cmpxchg_relaxed((ptr), (o), (n)) \ > }) > > -#define cmpxchg64_local(ptr, o, n) \ > -({ \ > - BUILD_BUG_ON(sizeof(*(ptr)) != 8); \ > - cmpxchg_local((ptr), (o), (n)); \ > +#define cmpxchg64(ptr, o, n) \ > +({ \ > + BUILD_BUG_ON(sizeof(*(ptr)) != 8); \ > + cmpxchg((ptr), (o), (n)); \ > +}) > + > +#define cmpxchg64_local(ptr, o, n) \ > +({ \ > + BUILD_BUG_ON(sizeof(*(ptr)) != 8); \ > + cmpxchg_relaxed((ptr), (o), (n)); \ > }) > > #endif /* _ASM_RISCV_CMPXCHG_H */