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git.ipfire.org Git - thirdparty/openssl.git/blob - include/internal/tsan_assist.h
2 * Copyright 2018-2022 The OpenSSL Project Authors. All Rights Reserved.
4 * Licensed under the Apache License 2.0 (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
11 * Contemporary compilers implement lock-free atomic memory access
12 * primitives that facilitate writing "thread-opportunistic" or even real
13 * multi-threading low-overhead code. "Thread-opportunistic" is when
14 * exact result is not required, e.g. some statistics, or execution flow
15 * doesn't have to be unambiguous. Simplest example is lazy "constant"
16 * initialization when one can synchronize on variable itself, e.g.
18 * if (var == NOT_YET_INITIALIZED)
19 * var = function_returning_same_value();
21 * This does work provided that loads and stores are single-instruction
22 * operations (and integer ones are on *all* supported platforms), but
23 * it upsets Thread Sanitizer. Suggested solution is
25 * if (tsan_load(&var) == NOT_YET_INITIALIZED)
26 * tsan_store(&var, function_returning_same_value());
28 * Production machine code would be the same, so one can wonder why
29 * bother. Having Thread Sanitizer accept "thread-opportunistic" code
30 * allows to move on trouble-shooting real bugs.
32 * Resolving Thread Sanitizer nits was the initial purpose for this module,
33 * but it was later extended with more nuanced primitives that are useful
34 * even in "non-opportunistic" scenarios. Most notably verifying if a shared
35 * structure is fully initialized and bypassing the initialization lock.
36 * It's suggested to view macros defined in this module as "annotations" for
37 * thread-safe lock-free code, "Thread-Safe ANnotations"...
39 * It's assumed that ATOMIC_{LONG|INT}_LOCK_FREE are assigned same value as
40 * ATOMIC_POINTER_LOCK_FREE. And check for >= 2 ensures that corresponding
41 * code is inlined. It should be noted that statistics counters become
42 * accurate in such case.
44 * Special note about TSAN_QUALIFIER. It might be undesired to use it in
45 * a shared header. Because whether operation on specific variable or member
46 * is atomic or not might be irrelevant in other modules. In such case one
47 * can use TSAN_QUALIFIER in cast specifically when it has to count.
50 #ifndef OSSL_INTERNAL_TSAN_ASSIST_H
51 # define OSSL_INTERNAL_TSAN_ASSIST_H
54 # if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L \
55 && !defined(__STDC_NO_ATOMICS__)
56 # include <stdatomic.h>
58 # if defined(ATOMIC_POINTER_LOCK_FREE) \
59 && ATOMIC_POINTER_LOCK_FREE >= 2
60 # define TSAN_QUALIFIER _Atomic
61 # define tsan_load(ptr) atomic_load_explicit((ptr), memory_order_relaxed)
62 # define tsan_store(ptr, val) atomic_store_explicit((ptr), (val), memory_order_relaxed)
63 # define tsan_add(ptr, n) atomic_fetch_add_explicit((ptr), (n), memory_order_relaxed)
64 # define tsan_ld_acq(ptr) atomic_load_explicit((ptr), memory_order_acquire)
65 # define tsan_st_rel(ptr, val) atomic_store_explicit((ptr), (val), memory_order_release)
68 # elif defined(__GNUC__) && defined(__ATOMIC_RELAXED)
70 # if defined(__GCC_ATOMIC_POINTER_LOCK_FREE) \
71 && __GCC_ATOMIC_POINTER_LOCK_FREE >= 2
72 # define TSAN_QUALIFIER volatile
73 # define tsan_load(ptr) __atomic_load_n((ptr), __ATOMIC_RELAXED)
74 # define tsan_store(ptr, val) __atomic_store_n((ptr), (val), __ATOMIC_RELAXED)
75 # define tsan_add(ptr, n) __atomic_fetch_add((ptr), (n), __ATOMIC_RELAXED)
76 # define tsan_ld_acq(ptr) __atomic_load_n((ptr), __ATOMIC_ACQUIRE)
77 # define tsan_st_rel(ptr, val) __atomic_store_n((ptr), (val), __ATOMIC_RELEASE)
80 # elif defined(_MSC_VER) && _MSC_VER>=1200 \
81 && (defined(_M_IX86) || defined(_M_AMD64) || defined(_M_X64) || \
82 defined(_M_ARM64) || (defined(_M_ARM) && _M_ARM >= 7 && !defined(_WIN32_WCE)))
84 * There is subtle dependency on /volatile:<iso|ms> command-line option.
85 * "ms" implies same semantic as memory_order_acquire for loads and
86 * memory_order_release for stores, while "iso" - memory_order_relaxed for
87 * either. Real complication is that defaults are different on x86 and ARM.
88 * There is explanation for that, "ms" is backward compatible with earlier
89 * compiler versions, while multi-processor ARM can be viewed as brand new
90 * platform to MSC and its users, and with non-relaxed semantic taking toll
91 * with additional instructions and penalties, it kind of makes sense to
94 # define TSAN_QUALIFIER volatile
95 # if defined(_M_ARM) || defined(_M_ARM64)
96 # define _InterlockedExchangeAdd _InterlockedExchangeAdd_nf
97 # pragma intrinsic(_InterlockedExchangeAdd_nf)
98 # pragma intrinsic(__iso_volatile_load32, __iso_volatile_store32)
100 # define _InterlockedExchangeAdd64 _InterlockedExchangeAdd64_nf
101 # pragma intrinsic(_InterlockedExchangeAdd64_nf)
102 # pragma intrinsic(__iso_volatile_load64, __iso_volatile_store64)
103 # define tsan_load(ptr) (sizeof(*(ptr)) == 8 ? __iso_volatile_load64(ptr) \
104 : __iso_volatile_load32(ptr))
105 # define tsan_store(ptr, val) (sizeof(*(ptr)) == 8 ? __iso_volatile_store64((ptr), (val)) \
106 : __iso_volatile_store32((ptr), (val)))
108 # define tsan_load(ptr) __iso_volatile_load32(ptr)
109 # define tsan_store(ptr, val) __iso_volatile_store32((ptr), (val))
112 # define tsan_load(ptr) (*(ptr))
113 # define tsan_store(ptr, val) (*(ptr) = (val))
115 # pragma intrinsic(_InterlockedExchangeAdd)
117 # pragma intrinsic(_InterlockedExchangeAdd64)
118 # define tsan_add(ptr, n) (sizeof(*(ptr)) == 8 ? _InterlockedExchangeAdd64((ptr), (n)) \
119 : _InterlockedExchangeAdd((ptr), (n)))
121 # define tsan_add(ptr, n) _InterlockedExchangeAdd((ptr), (n))
123 # if !defined(_ISO_VOLATILE)
124 # define tsan_ld_acq(ptr) (*(ptr))
125 # define tsan_st_rel(ptr, val) (*(ptr) = (val))
130 # ifndef TSAN_QUALIFIER
132 # ifdef OPENSSL_THREADS
133 # define TSAN_QUALIFIER volatile
134 # define TSAN_REQUIRES_LOCKING
135 # else /* OPENSSL_THREADS */
136 # define TSAN_QUALIFIER
137 # endif /* OPENSSL_THREADS */
139 # define tsan_load(ptr) (*(ptr))
140 # define tsan_store(ptr, val) (*(ptr) = (val))
141 # define tsan_add(ptr, n) (*(ptr) += (n))
143 * Lack of tsan_ld_acq and tsan_ld_rel means that compiler support is not
144 * sophisticated enough to support them. Code that relies on them should be
145 * protected with #ifdef tsan_ld_acq with locked fallback.
150 # define tsan_counter(ptr) tsan_add((ptr), 1)
151 # define tsan_decr(ptr) tsan_add((ptr), -1)