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Mon, 12 Jul 2021 08:59:19 -0700 (PDT) From: Richard Henderson To: qemu-devel@nongnu.org Subject: [PATCH 1/3] qemu/atomic: Remove pre-C11 atomic fallbacks Date: Mon, 12 Jul 2021 08:59:16 -0700 Message-Id: <20210712155918.1422519-2-richard.henderson@linaro.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210712155918.1422519-1-richard.henderson@linaro.org> References: <20210712155918.1422519-1-richard.henderson@linaro.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2607:f8b0:4864:20::42b; envelope-from=richard.henderson@linaro.org; helo=mail-pf1-x42b.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: peter.maydell@linaro.org, pbonzini@redhat.com, crobinso@redhat.com Errors-To: qemu-devel-bounces+patch=linaro.org@nongnu.org Sender: "Qemu-devel" We now require c11, so the fallbacks are now dead code Signed-off-by: Richard Henderson --- configure | 7 -- include/qemu/atomic.h | 204 +++--------------------------------------- 2 files changed, 10 insertions(+), 201 deletions(-) -- 2.25.1 diff --git a/configure b/configure index 85db248ac1..95e0a08938 100755 --- a/configure +++ b/configure @@ -3915,18 +3915,11 @@ cat > $TMPC << EOF int main(void) { uint64_t x = 0, y = 0; -#ifdef __ATOMIC_RELAXED y = __atomic_load_n(&x, __ATOMIC_RELAXED); __atomic_store_n(&x, y, __ATOMIC_RELAXED); __atomic_compare_exchange_n(&x, &y, x, 0, __ATOMIC_RELAXED, __ATOMIC_RELAXED); __atomic_exchange_n(&x, y, __ATOMIC_RELAXED); __atomic_fetch_add(&x, y, __ATOMIC_RELAXED); -#else - typedef char is_host64[sizeof(void *) >= sizeof(uint64_t) ? 1 : -1]; - __sync_lock_test_and_set(&x, y); - __sync_val_compare_and_swap(&x, y, 0); - __sync_fetch_and_add(&x, y); -#endif return 0; } EOF diff --git a/include/qemu/atomic.h b/include/qemu/atomic.h index 3ccf84fd46..c5d6df6bf8 100644 --- a/include/qemu/atomic.h +++ b/include/qemu/atomic.h @@ -60,8 +60,9 @@ (unsigned short)1, \ (expr)+0)))))) -#ifdef __ATOMIC_RELAXED -/* For C11 atomic ops */ +#ifndef __ATOMIC_RELAXED +#error "Expecting C11 atomic ops" +#endif /* Manual memory barriers * @@ -239,193 +240,8 @@ #define qatomic_xor(ptr, n) \ ((void) __atomic_fetch_xor(ptr, n, __ATOMIC_SEQ_CST)) -#else /* __ATOMIC_RELAXED */ - -#ifdef __alpha__ -#define smp_read_barrier_depends() asm volatile("mb":::"memory") -#endif - -#if defined(__i386__) || defined(__x86_64__) || defined(__s390x__) - -/* - * Because of the strongly ordered storage model, wmb() and rmb() are nops - * here (a compiler barrier only). QEMU doesn't do accesses to write-combining - * qemu memory or non-temporal load/stores from C code. - */ -#define smp_mb_release() barrier() -#define smp_mb_acquire() barrier() - -/* - * __sync_lock_test_and_set() is documented to be an acquire barrier only, - * but it is a full barrier at the hardware level. Add a compiler barrier - * to make it a full barrier also at the compiler level. - */ -#define qatomic_xchg(ptr, i) (barrier(), __sync_lock_test_and_set(ptr, i)) - -#elif defined(_ARCH_PPC) - -/* - * We use an eieio() for wmb() on powerpc. This assumes we don't - * need to order cacheable and non-cacheable stores with respect to - * each other. - * - * smp_mb has the same problem as on x86 for not-very-new GCC - * (http://patchwork.ozlabs.org/patch/126184/, Nov 2011). - */ -#define smp_wmb() ({ asm volatile("eieio" ::: "memory"); (void)0; }) -#if defined(__powerpc64__) -#define smp_mb_release() ({ asm volatile("lwsync" ::: "memory"); (void)0; }) -#define smp_mb_acquire() ({ asm volatile("lwsync" ::: "memory"); (void)0; }) -#else -#define smp_mb_release() ({ asm volatile("sync" ::: "memory"); (void)0; }) -#define smp_mb_acquire() ({ asm volatile("sync" ::: "memory"); (void)0; }) -#endif -#define smp_mb() ({ asm volatile("sync" ::: "memory"); (void)0; }) - -#endif /* _ARCH_PPC */ - -/* - * For (host) platforms we don't have explicit barrier definitions - * for, we use the gcc __sync_synchronize() primitive to generate a - * full barrier. This should be safe on all platforms, though it may - * be overkill for smp_mb_acquire() and smp_mb_release(). - */ -#ifndef smp_mb -#define smp_mb() __sync_synchronize() -#endif - -#ifndef smp_mb_acquire -#define smp_mb_acquire() __sync_synchronize() -#endif - -#ifndef smp_mb_release -#define smp_mb_release() __sync_synchronize() -#endif - -#ifndef smp_read_barrier_depends -#define smp_read_barrier_depends() barrier() -#endif - -#ifndef signal_barrier -#define signal_barrier() barrier() -#endif - -/* These will only be atomic if the processor does the fetch or store - * in a single issue memory operation - */ -#define qatomic_read__nocheck(p) (*(__typeof__(*(p)) volatile*) (p)) -#define qatomic_set__nocheck(p, i) ((*(__typeof__(*(p)) volatile*) (p)) = (i)) - -#define qatomic_read(ptr) qatomic_read__nocheck(ptr) -#define qatomic_set(ptr, i) qatomic_set__nocheck(ptr,i) - -/** - * qatomic_rcu_read - reads a RCU-protected pointer to a local variable - * into a RCU read-side critical section. The pointer can later be safely - * dereferenced within the critical section. - * - * This ensures that the pointer copy is invariant thorough the whole critical - * section. - * - * Inserts memory barriers on architectures that require them (currently only - * Alpha) and documents which pointers are protected by RCU. - * - * qatomic_rcu_read also includes a compiler barrier to ensure that - * value-speculative optimizations (e.g. VSS: Value Speculation - * Scheduling) does not perform the data read before the pointer read - * by speculating the value of the pointer. - * - * Should match qatomic_rcu_set(), qatomic_xchg(), qatomic_cmpxchg(). - */ -#define qatomic_rcu_read(ptr) ({ \ - typeof(*ptr) _val = qatomic_read(ptr); \ - smp_read_barrier_depends(); \ - _val; \ -}) - -/** - * qatomic_rcu_set - assigns (publicizes) a pointer to a new data structure - * meant to be read by RCU read-side critical sections. - * - * Documents which pointers will be dereferenced by RCU read-side critical - * sections and adds the required memory barriers on architectures requiring - * them. It also makes sure the compiler does not reorder code initializing the - * data structure before its publication. - * - * Should match qatomic_rcu_read(). - */ -#define qatomic_rcu_set(ptr, i) do { \ - smp_wmb(); \ - qatomic_set(ptr, i); \ -} while (0) - -#define qatomic_load_acquire(ptr) ({ \ - typeof(*ptr) _val = qatomic_read(ptr); \ - smp_mb_acquire(); \ - _val; \ -}) - -#define qatomic_store_release(ptr, i) do { \ - smp_mb_release(); \ - qatomic_set(ptr, i); \ -} while (0) - -#ifndef qatomic_xchg -#if defined(__clang__) -#define qatomic_xchg(ptr, i) __sync_swap(ptr, i) -#else -/* __sync_lock_test_and_set() is documented to be an acquire barrier only. */ -#define qatomic_xchg(ptr, i) (smp_mb(), __sync_lock_test_and_set(ptr, i)) -#endif -#endif -#define qatomic_xchg__nocheck qatomic_xchg - -/* Provide shorter names for GCC atomic builtins. */ -#define qatomic_fetch_inc(ptr) __sync_fetch_and_add(ptr, 1) -#define qatomic_fetch_dec(ptr) __sync_fetch_and_add(ptr, -1) - -#define qatomic_fetch_add(ptr, n) __sync_fetch_and_add(ptr, n) -#define qatomic_fetch_sub(ptr, n) __sync_fetch_and_sub(ptr, n) -#define qatomic_fetch_and(ptr, n) __sync_fetch_and_and(ptr, n) -#define qatomic_fetch_or(ptr, n) __sync_fetch_and_or(ptr, n) -#define qatomic_fetch_xor(ptr, n) __sync_fetch_and_xor(ptr, n) - -#define qatomic_inc_fetch(ptr) __sync_add_and_fetch(ptr, 1) -#define qatomic_dec_fetch(ptr) __sync_add_and_fetch(ptr, -1) -#define qatomic_add_fetch(ptr, n) __sync_add_and_fetch(ptr, n) -#define qatomic_sub_fetch(ptr, n) __sync_sub_and_fetch(ptr, n) -#define qatomic_and_fetch(ptr, n) __sync_and_and_fetch(ptr, n) -#define qatomic_or_fetch(ptr, n) __sync_or_and_fetch(ptr, n) -#define qatomic_xor_fetch(ptr, n) __sync_xor_and_fetch(ptr, n) - -#define qatomic_cmpxchg(ptr, old, new) \ - __sync_val_compare_and_swap(ptr, old, new) -#define qatomic_cmpxchg__nocheck(ptr, old, new) qatomic_cmpxchg(ptr, old, new) - -/* And even shorter names that return void. */ -#define qatomic_inc(ptr) ((void) __sync_fetch_and_add(ptr, 1)) -#define qatomic_dec(ptr) ((void) __sync_fetch_and_add(ptr, -1)) -#define qatomic_add(ptr, n) ((void) __sync_fetch_and_add(ptr, n)) -#define qatomic_sub(ptr, n) ((void) __sync_fetch_and_sub(ptr, n)) -#define qatomic_and(ptr, n) ((void) __sync_fetch_and_and(ptr, n)) -#define qatomic_or(ptr, n) ((void) __sync_fetch_and_or(ptr, n)) -#define qatomic_xor(ptr, n) ((void) __sync_fetch_and_xor(ptr, n)) - -#endif /* __ATOMIC_RELAXED */ - -#ifndef smp_wmb #define smp_wmb() smp_mb_release() -#endif -#ifndef smp_rmb #define smp_rmb() smp_mb_acquire() -#endif - -/* This is more efficient than a store plus a fence. */ -#if !defined(__SANITIZE_THREAD__) -#if defined(__i386__) || defined(__x86_64__) || defined(__s390x__) -#define qatomic_mb_set(ptr, i) ((void)qatomic_xchg(ptr, i)) -#endif -#endif /* qatomic_mb_read/set semantics map Java volatile variables. They are * less expensive on some platforms (notably POWER) than fully @@ -435,16 +251,16 @@ * use. See docs/devel/atomics.rst for more discussion. */ -#ifndef qatomic_mb_read #define qatomic_mb_read(ptr) \ qatomic_load_acquire(ptr) -#endif -#ifndef qatomic_mb_set -#define qatomic_mb_set(ptr, i) do { \ - qatomic_store_release(ptr, i); \ - smp_mb(); \ -} while(0) +#if !defined(__SANITIZE_THREAD__) && \ + (defined(__i386__) || defined(__x86_64__) || defined(__s390x__)) +/* This is more efficient than a store plus a fence. */ +# define qatomic_mb_set(ptr, i) ((void)qatomic_xchg(ptr, i)) +#else +# define qatomic_mb_set(ptr, i) \ + ({ qatomic_store_release(ptr, i); smp_mb(); }) #endif #define qatomic_fetch_inc_nonzero(ptr) ({ \