1 // Copyright 2020 The Pigweed Authors 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); you may not 4 // use this file except in compliance with the License. You may obtain a copy of 5 // the License at 6 // 7 // https://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 11 // WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the 12 // License for the specific language governing permissions and limitations under 13 // the License. 14 #pragma once 15 16 #include <stdbool.h> 17 18 #include "pw_preprocessor/util.h" 19 #include "pw_sync/lock_annotations.h" 20 21 #ifdef __cplusplus 22 23 #include "pw_sync/virtual_basic_lockable.h" 24 #include "pw_sync_backend/interrupt_spin_lock_native.h" 25 26 namespace pw::sync { 27 28 // The InterruptSpinLock is a synchronization primitive that can be used to 29 // protect shared data from being simultaneously accessed by multiple threads 30 // and/or interrupts as a targeted global lock, with the exception of 31 // Non-Maskable Interrupts (NMIs). 32 // It offers exclusive, non-recursive ownership semantics where IRQs up to a 33 // backend defined level of "NMIs" will be masked to solve priority-inversion. 34 // 35 // NOTE: This InterruptSpinLock relies on built-in local interrupt masking to 36 // make it interrupt safe without requiring the caller to separately mask and 37 // unmask interrupts when using this primitive. 38 // 39 // Unlike global interrupt locks, this also works safely and efficiently on SMP 40 // systems. On systems which are not SMP, spinning is not required and it's 41 // possible that only interrupt masking occurs but some state may still be used 42 // to detect recursion. 43 // 44 // This entire API is IRQ safe, but NOT NMI safe. 45 // 46 // Precondition: Code that holds a specific InterruptSpinLock must not try to 47 // re-acquire it. However, it is okay to nest distinct spinlocks. 48 class PW_LOCKABLE("pw::sync::InterruptSpinLock") InterruptSpinLock { 49 public: 50 using native_handle_type = backend::NativeInterruptSpinLockHandle; 51 52 constexpr InterruptSpinLock(); 53 ~InterruptSpinLock() = default; 54 InterruptSpinLock(const InterruptSpinLock&) = delete; 55 InterruptSpinLock(InterruptSpinLock&&) = delete; 56 InterruptSpinLock& operator=(const InterruptSpinLock&) = delete; 57 InterruptSpinLock& operator=(InterruptSpinLock&&) = delete; 58 59 // Locks the spinlock, blocking indefinitely. Failures are fatal. 60 // 61 // Precondition: Recursive locking is undefined behavior. 62 void lock() PW_EXCLUSIVE_LOCK_FUNCTION(); 63 64 // Tries to lock the spinlock in a non-blocking manner. 65 // Returns true if the spinlock was successfully acquired. 66 // 67 // Precondition: Recursive locking is undefined behavior. 68 bool try_lock() PW_EXCLUSIVE_TRYLOCK_FUNCTION(true); 69 70 // Unlocks the spinlock. Failures are fatal. 71 // 72 // PRECONDITION: 73 // The spinlock is held by the caller. 74 void unlock() PW_UNLOCK_FUNCTION(); 75 76 native_handle_type native_handle(); 77 78 private: 79 // This may be a wrapper around a native type with additional members. 80 backend::NativeInterruptSpinLock native_type_; 81 }; 82 83 class PW_LOCKABLE("pw::sync::VirtualInterruptSpinLock") 84 VirtualInterruptSpinLock final : public VirtualBasicLockable { 85 public: 86 VirtualInterruptSpinLock() = default; 87 88 VirtualInterruptSpinLock(const VirtualInterruptSpinLock&) = delete; 89 VirtualInterruptSpinLock(VirtualInterruptSpinLock&&) = delete; 90 VirtualInterruptSpinLock& operator=(const VirtualInterruptSpinLock&) = delete; 91 VirtualInterruptSpinLock& operator=(VirtualInterruptSpinLock&&) = delete; 92 interrupt_spin_lock()93 InterruptSpinLock& interrupt_spin_lock() { return interrupt_spin_lock_; } 94 95 private: DoLockOperation(Operation operation)96 void DoLockOperation(Operation operation) override 97 PW_NO_LOCK_SAFETY_ANALYSIS { 98 switch (operation) { 99 case Operation::kLock: 100 return interrupt_spin_lock_.lock(); 101 102 case Operation::kUnlock: 103 default: 104 return interrupt_spin_lock_.unlock(); 105 } 106 } 107 108 InterruptSpinLock interrupt_spin_lock_; 109 }; 110 111 } // namespace pw::sync 112 113 #include "pw_sync_backend/interrupt_spin_lock_inline.h" 114 115 using pw_sync_InterruptSpinLock = pw::sync::InterruptSpinLock; 116 117 #else // !defined(__cplusplus) 118 119 typedef struct pw_sync_InterruptSpinLock pw_sync_InterruptSpinLock; 120 121 #endif // __cplusplus 122 123 PW_EXTERN_C_START 124 125 void pw_sync_InterruptSpinLock_Lock(pw_sync_InterruptSpinLock* spin_lock) 126 PW_NO_LOCK_SAFETY_ANALYSIS; 127 bool pw_sync_InterruptSpinLock_TryLock(pw_sync_InterruptSpinLock* spin_lock) 128 PW_NO_LOCK_SAFETY_ANALYSIS; 129 void pw_sync_InterruptSpinLock_Unlock(pw_sync_InterruptSpinLock* spin_lock) 130 PW_NO_LOCK_SAFETY_ANALYSIS; 131 132 PW_EXTERN_C_END 133