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 37 /// and 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 /// @b Precondition: Code that holds a specific `InterruptSpinLock` must not try 47 /// to 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 /// @b 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 /// @b Precondition: Recursive locking is undefined behavior. 68 [[nodiscard]] bool try_lock() PW_EXCLUSIVE_TRYLOCK_FUNCTION(true); 69 70 /// Unlocks the spinlock. Failures are fatal. 71 /// 72 /// @b Precondition: 73 /// The spinlock is held by the caller. 74 void unlock() PW_UNLOCK_FUNCTION(); 75 76 [[nodiscard]] 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 85 : public GenericBasicLockable<InterruptSpinLock> {}; 86 87 } // namespace pw::sync 88 89 #include "pw_sync_backend/interrupt_spin_lock_inline.h" 90 91 using pw_sync_InterruptSpinLock = pw::sync::InterruptSpinLock; 92 93 #else // !defined(__cplusplus) 94 95 typedef struct pw_sync_InterruptSpinLock pw_sync_InterruptSpinLock; 96 97 #endif // __cplusplus 98 99 PW_EXTERN_C_START 100 101 /// Invokes the `InterruptSpinLock::lock` member function on the given 102 /// `interrupt_spin_lock`. 103 void pw_sync_InterruptSpinLock_Lock(pw_sync_InterruptSpinLock* spin_lock) 104 PW_NO_LOCK_SAFETY_ANALYSIS; 105 106 /// Invokes the `InterruptSpinLock::try_lock` member function on the given 107 /// `interrupt_spin_lock`. 108 bool pw_sync_InterruptSpinLock_TryLock(pw_sync_InterruptSpinLock* spin_lock) 109 PW_NO_LOCK_SAFETY_ANALYSIS; 110 111 /// Invokes the `InterruptSpinLock::unlock` member function on the given 112 /// `interrupt_spin_lock`. 113 void pw_sync_InterruptSpinLock_Unlock(pw_sync_InterruptSpinLock* spin_lock) 114 PW_NO_LOCK_SAFETY_ANALYSIS; 115 116 PW_EXTERN_C_END 117