| /* |
| * Simple interface for atomic operations. |
| * |
| * Copyright (C) 2013 Red Hat, Inc. |
| * |
| * Author: Paolo Bonzini <pbonzini@redhat.com> |
| * |
| * This work is licensed under the terms of the GNU GPL, version 2 or later. |
| * See the COPYING file in the top-level directory. |
| * |
| * See docs/devel/atomics.rst for discussion about the guarantees each |
| * atomic primitive is meant to provide. |
| */ |
| |
| #ifndef QEMU_ATOMIC_H |
| #define QEMU_ATOMIC_H |
| |
| #include "compiler.h" |
| |
| /* Compiler barrier */ |
| #define barrier() ({ asm volatile("" ::: "memory"); (void)0; }) |
| |
| /* The variable that receives the old value of an atomically-accessed |
| * variable must be non-qualified, because atomic builtins return values |
| * through a pointer-type argument as in __atomic_load(&var, &old, MODEL). |
| * |
| * This macro has to handle types smaller than int manually, because of |
| * implicit promotion. int and larger types, as well as pointers, can be |
| * converted to a non-qualified type just by applying a binary operator. |
| */ |
| #define typeof_strip_qual(expr) \ |
| typeof( \ |
| __builtin_choose_expr( \ |
| __builtin_types_compatible_p(typeof(expr), bool) || \ |
| __builtin_types_compatible_p(typeof(expr), const bool) || \ |
| __builtin_types_compatible_p(typeof(expr), volatile bool) || \ |
| __builtin_types_compatible_p(typeof(expr), const volatile bool), \ |
| (bool)1, \ |
| __builtin_choose_expr( \ |
| __builtin_types_compatible_p(typeof(expr), signed char) || \ |
| __builtin_types_compatible_p(typeof(expr), const signed char) || \ |
| __builtin_types_compatible_p(typeof(expr), volatile signed char) || \ |
| __builtin_types_compatible_p(typeof(expr), const volatile signed char), \ |
| (signed char)1, \ |
| __builtin_choose_expr( \ |
| __builtin_types_compatible_p(typeof(expr), unsigned char) || \ |
| __builtin_types_compatible_p(typeof(expr), const unsigned char) || \ |
| __builtin_types_compatible_p(typeof(expr), volatile unsigned char) || \ |
| __builtin_types_compatible_p(typeof(expr), const volatile unsigned char), \ |
| (unsigned char)1, \ |
| __builtin_choose_expr( \ |
| __builtin_types_compatible_p(typeof(expr), signed short) || \ |
| __builtin_types_compatible_p(typeof(expr), const signed short) || \ |
| __builtin_types_compatible_p(typeof(expr), volatile signed short) || \ |
| __builtin_types_compatible_p(typeof(expr), const volatile signed short), \ |
| (signed short)1, \ |
| __builtin_choose_expr( \ |
| __builtin_types_compatible_p(typeof(expr), unsigned short) || \ |
| __builtin_types_compatible_p(typeof(expr), const unsigned short) || \ |
| __builtin_types_compatible_p(typeof(expr), volatile unsigned short) || \ |
| __builtin_types_compatible_p(typeof(expr), const volatile unsigned short), \ |
| (unsigned short)1, \ |
| (expr)+0)))))) |
| |
| #ifndef __ATOMIC_RELAXED |
| #error "Expecting C11 atomic ops" |
| #endif |
| |
| /* Manual memory barriers |
| * |
| *__atomic_thread_fence does not include a compiler barrier; instead, |
| * the barrier is part of __atomic_load/__atomic_store's "volatile-like" |
| * semantics. If smp_wmb() is a no-op, absence of the barrier means that |
| * the compiler is free to reorder stores on each side of the barrier. |
| * Add one here, and similarly in smp_rmb() and smp_read_barrier_depends(). |
| */ |
| |
| #define smp_mb() ({ barrier(); __atomic_thread_fence(__ATOMIC_SEQ_CST); }) |
| #define smp_mb_release() ({ barrier(); __atomic_thread_fence(__ATOMIC_RELEASE); }) |
| #define smp_mb_acquire() ({ barrier(); __atomic_thread_fence(__ATOMIC_ACQUIRE); }) |
| |
| /* Most compilers currently treat consume and acquire the same, but really |
| * no processors except Alpha need a barrier here. Leave it in if |
| * using Thread Sanitizer to avoid warnings, otherwise optimize it away. |
| */ |
| #ifdef QEMU_SANITIZE_THREAD |
| #define smp_read_barrier_depends() ({ barrier(); __atomic_thread_fence(__ATOMIC_CONSUME); }) |
| #elif defined(__alpha__) |
| #define smp_read_barrier_depends() asm volatile("mb":::"memory") |
| #else |
| #define smp_read_barrier_depends() barrier() |
| #endif |
| |
| /* |
| * A signal barrier forces all pending local memory ops to be observed before |
| * a SIGSEGV is delivered to the *same* thread. In practice this is exactly |
| * the same as barrier(), but since we have the correct builtin, use it. |
| */ |
| #define signal_barrier() __atomic_signal_fence(__ATOMIC_SEQ_CST) |
| |
| /* Sanity check that the size of an atomic operation isn't "overly large". |
| * Despite the fact that e.g. i686 has 64-bit atomic operations, we do not |
| * want to use them because we ought not need them, and this lets us do a |
| * bit of sanity checking that other 32-bit hosts might build. |
| * |
| * That said, we have a problem on 64-bit ILP32 hosts in that in order to |
| * sync with TCG_OVERSIZED_GUEST, this must match TCG_TARGET_REG_BITS. |
| * We'd prefer not want to pull in everything else TCG related, so handle |
| * those few cases by hand. |
| * |
| * Note that x32 is fully detected with __x86_64__ + _ILP32, and that for |
| * Sparc we always force the use of sparcv9 in configure. MIPS n32 (ILP32) & |
| * n64 (LP64) ABIs are both detected using __mips64. |
| */ |
| #if defined(__x86_64__) || defined(__sparc__) || defined(__mips64) |
| # define ATOMIC_REG_SIZE 8 |
| #else |
| # define ATOMIC_REG_SIZE sizeof(void *) |
| #endif |
| |
| /* Weak atomic operations prevent the compiler moving other |
| * loads/stores past the atomic operation load/store. However there is |
| * no explicit memory barrier for the processor. |
| * |
| * The C11 memory model says that variables that are accessed from |
| * different threads should at least be done with __ATOMIC_RELAXED |
| * primitives or the result is undefined. Generally this has little to |
| * no effect on the generated code but not using the atomic primitives |
| * will get flagged by sanitizers as a violation. |
| */ |
| #define qatomic_read__nocheck(ptr) \ |
| __atomic_load_n(ptr, __ATOMIC_RELAXED) |
| |
| #define qatomic_read(ptr) \ |
| ({ \ |
| qemu_build_assert(sizeof(*ptr) <= ATOMIC_REG_SIZE); \ |
| qatomic_read__nocheck(ptr); \ |
| }) |
| |
| #define qatomic_set__nocheck(ptr, i) \ |
| __atomic_store_n(ptr, i, __ATOMIC_RELAXED) |
| |
| #define qatomic_set(ptr, i) do { \ |
| qemu_build_assert(sizeof(*ptr) <= ATOMIC_REG_SIZE); \ |
| qatomic_set__nocheck(ptr, i); \ |
| } while(0) |
| |
| /* See above: most compilers currently treat consume and acquire the |
| * same, but this slows down qatomic_rcu_read unnecessarily. |
| */ |
| #ifdef QEMU_SANITIZE_THREAD |
| #define qatomic_rcu_read__nocheck(ptr, valptr) \ |
| __atomic_load(ptr, valptr, __ATOMIC_CONSUME); |
| #else |
| #define qatomic_rcu_read__nocheck(ptr, valptr) \ |
| __atomic_load(ptr, valptr, __ATOMIC_RELAXED); \ |
| smp_read_barrier_depends(); |
| #endif |
| |
| #define qatomic_rcu_read(ptr) \ |
| ({ \ |
| qemu_build_assert(sizeof(*ptr) <= ATOMIC_REG_SIZE); \ |
| typeof_strip_qual(*ptr) _val; \ |
| qatomic_rcu_read__nocheck(ptr, &_val); \ |
| _val; \ |
| }) |
| |
| #define qatomic_rcu_set(ptr, i) do { \ |
| qemu_build_assert(sizeof(*ptr) <= ATOMIC_REG_SIZE); \ |
| __atomic_store_n(ptr, i, __ATOMIC_RELEASE); \ |
| } while(0) |
| |
| #define qatomic_load_acquire(ptr) \ |
| ({ \ |
| qemu_build_assert(sizeof(*ptr) <= ATOMIC_REG_SIZE); \ |
| typeof_strip_qual(*ptr) _val; \ |
| __atomic_load(ptr, &_val, __ATOMIC_ACQUIRE); \ |
| _val; \ |
| }) |
| |
| #define qatomic_store_release(ptr, i) do { \ |
| qemu_build_assert(sizeof(*ptr) <= ATOMIC_REG_SIZE); \ |
| __atomic_store_n(ptr, i, __ATOMIC_RELEASE); \ |
| } while(0) |
| |
| |
| /* All the remaining operations are fully sequentially consistent */ |
| |
| #define qatomic_xchg__nocheck(ptr, i) ({ \ |
| __atomic_exchange_n(ptr, (i), __ATOMIC_SEQ_CST); \ |
| }) |
| |
| #define qatomic_xchg(ptr, i) ({ \ |
| qemu_build_assert(sizeof(*ptr) <= ATOMIC_REG_SIZE); \ |
| qatomic_xchg__nocheck(ptr, i); \ |
| }) |
| |
| /* Returns the eventual value, failed or not */ |
| #define qatomic_cmpxchg__nocheck(ptr, old, new) ({ \ |
| typeof_strip_qual(*ptr) _old = (old); \ |
| (void)__atomic_compare_exchange_n(ptr, &_old, new, false, \ |
| __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST); \ |
| _old; \ |
| }) |
| |
| #define qatomic_cmpxchg(ptr, old, new) ({ \ |
| qemu_build_assert(sizeof(*ptr) <= ATOMIC_REG_SIZE); \ |
| qatomic_cmpxchg__nocheck(ptr, old, new); \ |
| }) |
| |
| /* Provide shorter names for GCC atomic builtins, return old value */ |
| #define qatomic_fetch_inc(ptr) __atomic_fetch_add(ptr, 1, __ATOMIC_SEQ_CST) |
| #define qatomic_fetch_dec(ptr) __atomic_fetch_sub(ptr, 1, __ATOMIC_SEQ_CST) |
| |
| #define qatomic_fetch_add(ptr, n) __atomic_fetch_add(ptr, n, __ATOMIC_SEQ_CST) |
| #define qatomic_fetch_sub(ptr, n) __atomic_fetch_sub(ptr, n, __ATOMIC_SEQ_CST) |
| #define qatomic_fetch_and(ptr, n) __atomic_fetch_and(ptr, n, __ATOMIC_SEQ_CST) |
| #define qatomic_fetch_or(ptr, n) __atomic_fetch_or(ptr, n, __ATOMIC_SEQ_CST) |
| #define qatomic_fetch_xor(ptr, n) __atomic_fetch_xor(ptr, n, __ATOMIC_SEQ_CST) |
| |
| #define qatomic_inc_fetch(ptr) __atomic_add_fetch(ptr, 1, __ATOMIC_SEQ_CST) |
| #define qatomic_dec_fetch(ptr) __atomic_sub_fetch(ptr, 1, __ATOMIC_SEQ_CST) |
| #define qatomic_add_fetch(ptr, n) __atomic_add_fetch(ptr, n, __ATOMIC_SEQ_CST) |
| #define qatomic_sub_fetch(ptr, n) __atomic_sub_fetch(ptr, n, __ATOMIC_SEQ_CST) |
| #define qatomic_and_fetch(ptr, n) __atomic_and_fetch(ptr, n, __ATOMIC_SEQ_CST) |
| #define qatomic_or_fetch(ptr, n) __atomic_or_fetch(ptr, n, __ATOMIC_SEQ_CST) |
| #define qatomic_xor_fetch(ptr, n) __atomic_xor_fetch(ptr, n, __ATOMIC_SEQ_CST) |
| |
| /* And even shorter names that return void. */ |
| #define qatomic_inc(ptr) \ |
| ((void) __atomic_fetch_add(ptr, 1, __ATOMIC_SEQ_CST)) |
| #define qatomic_dec(ptr) \ |
| ((void) __atomic_fetch_sub(ptr, 1, __ATOMIC_SEQ_CST)) |
| #define qatomic_add(ptr, n) \ |
| ((void) __atomic_fetch_add(ptr, n, __ATOMIC_SEQ_CST)) |
| #define qatomic_sub(ptr, n) \ |
| ((void) __atomic_fetch_sub(ptr, n, __ATOMIC_SEQ_CST)) |
| #define qatomic_and(ptr, n) \ |
| ((void) __atomic_fetch_and(ptr, n, __ATOMIC_SEQ_CST)) |
| #define qatomic_or(ptr, n) \ |
| ((void) __atomic_fetch_or(ptr, n, __ATOMIC_SEQ_CST)) |
| #define qatomic_xor(ptr, n) \ |
| ((void) __atomic_fetch_xor(ptr, n, __ATOMIC_SEQ_CST)) |
| |
| #define smp_wmb() smp_mb_release() |
| #define smp_rmb() smp_mb_acquire() |
| |
| /* |
| * SEQ_CST is weaker than the older __sync_* builtins and Linux |
| * kernel read-modify-write atomics. Provide a macro to obtain |
| * the same semantics. |
| */ |
| #if !defined(QEMU_SANITIZE_THREAD) && \ |
| (defined(__i386__) || defined(__x86_64__) || defined(__s390x__)) |
| # define smp_mb__before_rmw() signal_barrier() |
| # define smp_mb__after_rmw() signal_barrier() |
| #else |
| # define smp_mb__before_rmw() smp_mb() |
| # define smp_mb__after_rmw() smp_mb() |
| #endif |
| |
| /* qatomic_mb_read/set semantics map Java volatile variables. They are |
| * less expensive on some platforms (notably POWER) than fully |
| * sequentially consistent operations. |
| * |
| * As long as they are used as paired operations they are safe to |
| * use. See docs/devel/atomics.rst for more discussion. |
| */ |
| |
| #define qatomic_mb_read(ptr) \ |
| qatomic_load_acquire(ptr) |
| |
| #if !defined(QEMU_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); smp_mb__after_rmw(); }) |
| #else |
| # define qatomic_mb_set(ptr, i) \ |
| ({ qatomic_store_release(ptr, i); smp_mb(); }) |
| #endif |
| |
| #define qatomic_fetch_inc_nonzero(ptr) ({ \ |
| typeof_strip_qual(*ptr) _oldn = qatomic_read(ptr); \ |
| while (_oldn && qatomic_cmpxchg(ptr, _oldn, _oldn + 1) != _oldn) { \ |
| _oldn = qatomic_read(ptr); \ |
| } \ |
| _oldn; \ |
| }) |
| |
| /* |
| * Abstractions to access atomically (i.e. "once") i64/u64 variables. |
| * |
| * The i386 abi is odd in that by default members are only aligned to |
| * 4 bytes, which means that 8-byte types can wind up mis-aligned. |
| * Clang will then warn about this, and emit a call into libatomic. |
| * |
| * Use of these types in structures when they will be used with atomic |
| * operations can avoid this. |
| */ |
| typedef int64_t aligned_int64_t __attribute__((aligned(8))); |
| typedef uint64_t aligned_uint64_t __attribute__((aligned(8))); |
| |
| #ifdef CONFIG_ATOMIC64 |
| /* Use __nocheck because sizeof(void *) might be < sizeof(u64) */ |
| #define qatomic_read_i64(P) \ |
| _Generic(*(P), int64_t: qatomic_read__nocheck(P)) |
| #define qatomic_read_u64(P) \ |
| _Generic(*(P), uint64_t: qatomic_read__nocheck(P)) |
| #define qatomic_set_i64(P, V) \ |
| _Generic(*(P), int64_t: qatomic_set__nocheck(P, V)) |
| #define qatomic_set_u64(P, V) \ |
| _Generic(*(P), uint64_t: qatomic_set__nocheck(P, V)) |
| |
| static inline void qatomic64_init(void) |
| { |
| } |
| #else /* !CONFIG_ATOMIC64 */ |
| int64_t qatomic_read_i64(const int64_t *ptr); |
| uint64_t qatomic_read_u64(const uint64_t *ptr); |
| void qatomic_set_i64(int64_t *ptr, int64_t val); |
| void qatomic_set_u64(uint64_t *ptr, uint64_t val); |
| void qatomic64_init(void); |
| #endif /* !CONFIG_ATOMIC64 */ |
| |
| #endif /* QEMU_ATOMIC_H */ |
