From 5d8dfe892a2ea89f706ee140c3bdcfd89fe03fda Mon Sep 17 00:00:00 2001 From: Mitja Felicijan Date: Wed, 21 Jan 2026 22:40:55 +0100 Subject: Add Redis source code for testing --- examples/redis-unstable/src/atomicvar.h | 186 ++++++++++++++++++++++++++++++++ 1 file changed, 186 insertions(+) create mode 100644 examples/redis-unstable/src/atomicvar.h (limited to 'examples/redis-unstable/src/atomicvar.h') diff --git a/examples/redis-unstable/src/atomicvar.h b/examples/redis-unstable/src/atomicvar.h new file mode 100644 index 0000000..3c332ee --- /dev/null +++ b/examples/redis-unstable/src/atomicvar.h @@ -0,0 +1,186 @@ +/* This file implements atomic counters using c11 _Atomic, __atomic or __sync + * macros if available, otherwise we will throw an error when compile. + * + * The exported interface is composed of the following macros: + * + * atomicIncr(var,count) -- Increment the atomic counter + * atomicGetIncr(var,oldvalue_var,count) -- Get and increment the atomic counter + * atomicIncrGet(var,newvalue_var,count) -- Increment and get the atomic counter new value + * atomicDecr(var,count) -- Decrement the atomic counter + * atomicGet(var,dstvar) -- Fetch the atomic counter value + * atomicSet(var,value) -- Set the atomic counter value + * atomicGetWithSync(var,value) -- 'atomicGet' with inter-thread synchronization + * atomicSetWithSync(var,value) -- 'atomicSet' with inter-thread synchronization + * atomicCompareExchange(type,var,expected_var,desired) -- Compare and exchange (CAS) operation + * + * Atomic operations on flags. + * Flag type can be int, long, long long or their unsigned counterparts. + * The value of the flag can be 1 or 0. + * + * atomicFlagGetSet(var,oldvalue_var) -- Get and set the atomic counter value + * + * NOTE1: __atomic* and _Atomic implementations can be actually elaborated to support any value by changing the + * hardcoded new value passed to __atomic_exchange* from 1 to @param count + * i.e oldvalue_var = atomic_exchange_explicit(&var, count). + * However, in order to be compatible with the __sync functions family, we can use only 0 and 1. + * The only exchange alternative suggested by __sync is __sync_lock_test_and_set, + * But as described by the gnu manual for __sync_lock_test_and_set(): + * https://gcc.gnu.org/onlinedocs/gcc/_005f_005fsync-Builtins.html + * "A target may support reduced functionality here by which the only valid value to store is the immediate constant 1. The exact value + * actually stored in *ptr is implementation defined." + * Hence, we can't rely on it for a any value other than 1. + * We eventually chose to implement this method with __sync_val_compare_and_swap since it satisfies functionality needed for atomicFlagGetSet + * (if the flag was 0 -> set to 1, if it's already 1 -> do nothing, but the final result is that the flag is set), + * and also it has a full barrier (__sync_lock_test_and_set has acquire barrier). + * + * NOTE2: Unlike other atomic type, which aren't guaranteed to be lock free, c11 atomic_flag does. + * To check whether a type is lock free, atomic_is_lock_free() can be used. + * It can be considered to limit the flag type to atomic_flag to improve performance. + * + * Never use return value from the macros, instead use the AtomicGetIncr() + * if you need to get the current value and increment it atomically, like + * in the following example: + * + * long oldvalue; + * atomicGetIncr(myvar,oldvalue,1); + * doSomethingWith(oldvalue); + * + * ---------------------------------------------------------------------------- + * + * Copyright (c) 2015-Present, Redis Ltd. + * All rights reserved. + * + * Licensed under your choice of (a) the Redis Source Available License 2.0 + * (RSALv2); or (b) the Server Side Public License v1 (SSPLv1); or (c) the + * GNU Affero General Public License v3 (AGPLv3). + */ + +#include +#include "config.h" + +#ifndef __ATOMIC_VAR_H +#define __ATOMIC_VAR_H + +/* Define redisAtomic for atomic variable. */ +#define redisAtomic + +/* To test Redis with Helgrind (a Valgrind tool) it is useful to define + * the following macro, so that __sync macros are used: those can be detected + * by Helgrind (even if they are less efficient) so that no false positive + * is reported. */ +// #define __ATOMIC_VAR_FORCE_SYNC_MACROS + +/* There will be many false positives if we test Redis with Helgrind, since + * Helgrind can't understand we have imposed ordering on the program, so + * we use macros in helgrind.h to tell Helgrind inter-thread happens-before + * relationship explicitly for avoiding false positives. + * + * For more details, please see: valgrind/helgrind.h and + * https://www.valgrind.org/docs/manual/hg-manual.html#hg-manual.effective-use + * + * These macros take effect only when 'make helgrind', and you must first + * install Valgrind in the default path configuration. */ +#ifdef __ATOMIC_VAR_FORCE_SYNC_MACROS +#include +#else +#define ANNOTATE_HAPPENS_BEFORE(v) ((void) v) +#define ANNOTATE_HAPPENS_AFTER(v) ((void) v) +#endif + +#if !defined(__ATOMIC_VAR_FORCE_SYNC_MACROS) && defined(__STDC_VERSION__) && \ + (__STDC_VERSION__ >= 201112L) && !defined(__STDC_NO_ATOMICS__) +/* Use '_Atomic' keyword if the compiler supports. */ +#undef redisAtomic +#define redisAtomic _Atomic +/* Implementation using _Atomic in C11. */ + +#include +#define atomicIncr(var,count) atomic_fetch_add_explicit(&var,(count),memory_order_relaxed) +#define atomicGetIncr(var,oldvalue_var,count) do { \ + oldvalue_var = atomic_fetch_add_explicit(&var,(count),memory_order_relaxed); \ +} while(0) +#define atomicIncrGet(var, newvalue_var, count) \ + newvalue_var = atomicIncr(var,count) + count +#define atomicDecr(var,count) atomic_fetch_sub_explicit(&var,(count),memory_order_relaxed) +#define atomicGet(var,dstvar) do { \ + dstvar = atomic_load_explicit(&var,memory_order_relaxed); \ +} while(0) +#define atomicSet(var,value) atomic_store_explicit(&var,value,memory_order_relaxed) +#define atomicGetWithSync(var,dstvar) do { \ + dstvar = atomic_load_explicit(&var,memory_order_seq_cst); \ +} while(0) +#define atomicSetWithSync(var,value) \ + atomic_store_explicit(&var,value,memory_order_seq_cst) +#define atomicCompareExchange(type,var,expected_var,desired) \ + atomic_compare_exchange_weak_explicit(&var,&expected_var,desired,memory_order_relaxed,memory_order_relaxed) +#define atomicFlagGetSet(var,oldvalue_var) \ + oldvalue_var = atomic_exchange_explicit(&var,1,memory_order_relaxed) +#define REDIS_ATOMIC_API "c11-builtin" + +#elif !defined(__ATOMIC_VAR_FORCE_SYNC_MACROS) && \ + (!defined(__clang__) || !defined(__APPLE__) || __apple_build_version__ > 4210057) && \ + defined(__ATOMIC_RELAXED) && defined(__ATOMIC_SEQ_CST) +/* Implementation using __atomic macros. */ + +#define atomicIncr(var,count) __atomic_add_fetch(&var,(count),__ATOMIC_RELAXED) +#define atomicIncrGet(var, newvalue_var, count) \ + newvalue_var = __atomic_add_fetch(&var,(count),__ATOMIC_RELAXED) +#define atomicGetIncr(var,oldvalue_var,count) do { \ + oldvalue_var = __atomic_fetch_add(&var,(count),__ATOMIC_RELAXED); \ +} while(0) +#define atomicDecr(var,count) __atomic_sub_fetch(&var,(count),__ATOMIC_RELAXED) +#define atomicGet(var,dstvar) do { \ + dstvar = __atomic_load_n(&var,__ATOMIC_RELAXED); \ +} while(0) +#define atomicSet(var,value) __atomic_store_n(&var,value,__ATOMIC_RELAXED) +#define atomicGetWithSync(var,dstvar) do { \ + dstvar = __atomic_load_n(&var,__ATOMIC_SEQ_CST); \ +} while(0) +#define atomicSetWithSync(var,value) \ + __atomic_store_n(&var,value,__ATOMIC_SEQ_CST) +#define atomicCompareExchange(type,var,expected_var,desired) \ + __atomic_compare_exchange_n(&var,&expected_var,desired,1,__ATOMIC_RELAXED,__ATOMIC_RELAXED) +#define atomicFlagGetSet(var,oldvalue_var) \ + oldvalue_var = __atomic_exchange_n(&var,1,__ATOMIC_RELAXED) +#define REDIS_ATOMIC_API "atomic-builtin" + +#elif defined(HAVE_ATOMIC) +/* Implementation using __sync macros. */ + +#define atomicIncr(var,count) __sync_add_and_fetch(&var,(count)) +#define atomicIncrGet(var, newvalue_var, count) \ + newvalue_var = __sync_add_and_fetch(&var,(count)) +#define atomicGetIncr(var,oldvalue_var,count) do { \ + oldvalue_var = __sync_fetch_and_add(&var,(count)); \ +} while(0) +#define atomicDecr(var,count) __sync_sub_and_fetch(&var,(count)) +#define atomicGet(var,dstvar) do { \ + dstvar = __sync_sub_and_fetch(&var,0); \ +} while(0) +#define atomicSet(var,value) do { \ + while(!__sync_bool_compare_and_swap(&var,var,value)); \ +} while(0) +/* Actually the builtin issues a full memory barrier by default. */ +#define atomicGetWithSync(var,dstvar) do { \ + dstvar = __sync_sub_and_fetch(&var,0,__sync_synchronize); \ + ANNOTATE_HAPPENS_AFTER(&var); \ +} while(0) +#define atomicSetWithSync(var,value) do { \ + ANNOTATE_HAPPENS_BEFORE(&var); \ + while(!__sync_bool_compare_and_swap(&var,var,value,__sync_synchronize)); \ +} while(0) +#define atomicCompareExchange(type,var,expected_var,desired) ({ \ + type _old = __sync_val_compare_and_swap(&var,expected_var,desired); \ + int _success = (_old == expected_var); \ + if (!_success) expected_var = _old; \ + _success; \ +}) +#define atomicFlagGetSet(var,oldvalue_var) \ + oldvalue_var = __sync_val_compare_and_swap(&var,0,1) +#define REDIS_ATOMIC_API "sync-builtin" + +#else +#error "Unable to determine atomic operations for your platform" + +#endif +#endif /* __ATOMIC_VAR_H */ -- cgit v1.2.3