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// Copyright 2020 The Pigweed Authors
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
#pragma once
#include <stdbool.h>
#include "pw_preprocessor/util.h"
#include "pw_sync/lock_annotations.h"
#ifdef __cplusplus
#include "pw_sync/virtual_basic_lockable.h"
#include "pw_sync_backend/interrupt_spin_lock_native.h"
namespace pw::sync {
/// The `InterruptSpinLock` is a synchronization primitive that can be used to
/// protect shared data from being simultaneously accessed by multiple threads
/// and/or interrupts as a targeted global lock, with the exception of
/// Non-Maskable Interrupts (NMIs).
/// It offers exclusive, non-recursive ownership semantics where IRQs up to a
/// backend defined level of "NMIs" will be masked to solve priority-inversion.
///
/// @note This `InterruptSpinLock` relies on built-in local interrupt masking to
/// make it interrupt safe without requiring the caller to separately mask
/// and unmask interrupts when using this primitive.
///
/// Unlike global interrupt locks, this also works safely and efficiently on SMP
/// systems. On systems which are not SMP, spinning is not required and it's
/// possible that only interrupt masking occurs but some state may still be used
/// to detect recursion.
///
/// This entire API is IRQ safe, but NOT NMI safe.
///
/// @b Precondition: Code that holds a specific `InterruptSpinLock` must not try
/// to re-acquire it. However, it is okay to nest distinct spinlocks.
class PW_LOCKABLE("pw::sync::InterruptSpinLock") InterruptSpinLock {
public:
using native_handle_type = backend::NativeInterruptSpinLockHandle;
constexpr InterruptSpinLock();
~InterruptSpinLock() = default;
InterruptSpinLock(const InterruptSpinLock&) = delete;
InterruptSpinLock(InterruptSpinLock&&) = delete;
InterruptSpinLock& operator=(const InterruptSpinLock&) = delete;
InterruptSpinLock& operator=(InterruptSpinLock&&) = delete;
/// Locks the spinlock, blocking indefinitely. Failures are fatal.
///
/// @b Precondition: Recursive locking is undefined behavior.
void lock() PW_EXCLUSIVE_LOCK_FUNCTION();
/// Tries to lock the spinlock in a non-blocking manner.
/// Returns true if the spinlock was successfully acquired.
///
/// @b Precondition: Recursive locking is undefined behavior.
bool try_lock() PW_EXCLUSIVE_TRYLOCK_FUNCTION(true);
/// Unlocks the spinlock. Failures are fatal.
///
/// @b Precondition:
/// The spinlock is held by the caller.
void unlock() PW_UNLOCK_FUNCTION();
native_handle_type native_handle();
private:
/// This may be a wrapper around a native type with additional members.
backend::NativeInterruptSpinLock native_type_;
};
class PW_LOCKABLE("pw::sync::VirtualInterruptSpinLock")
VirtualInterruptSpinLock final
: public GenericBasicLockable<InterruptSpinLock> {};
} // namespace pw::sync
#include "pw_sync_backend/interrupt_spin_lock_inline.h"
using pw_sync_InterruptSpinLock = pw::sync::InterruptSpinLock;
#else // !defined(__cplusplus)
typedef struct pw_sync_InterruptSpinLock pw_sync_InterruptSpinLock;
#endif // __cplusplus
PW_EXTERN_C_START
/// Invokes the `InterruptSpinLock::lock` member function on the given
/// `interrupt_spin_lock`.
void pw_sync_InterruptSpinLock_Lock(pw_sync_InterruptSpinLock* spin_lock)
PW_NO_LOCK_SAFETY_ANALYSIS;
/// Invokes the `InterruptSpinLock::try_lock` member function on the given
/// `interrupt_spin_lock`.
bool pw_sync_InterruptSpinLock_TryLock(pw_sync_InterruptSpinLock* spin_lock)
PW_NO_LOCK_SAFETY_ANALYSIS;
/// Invokes the `InterruptSpinLock::unlock` member function on the given
/// `interrupt_spin_lock`.
void pw_sync_InterruptSpinLock_Unlock(pw_sync_InterruptSpinLock* spin_lock)
PW_NO_LOCK_SAFETY_ANALYSIS;
PW_EXTERN_C_END
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