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https://fuchsia.googlesource.com/third_party/pigweed.googlesource.com/pigweed/pigweed
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58 lines
2.0 KiB
C++
58 lines
2.0 KiB
C++
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// Copyright 2020 The Pigweed Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not
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// use this file except in compliance with the License. You may obtain a copy of
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// the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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// License for the specific language governing permissions and limitations under
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// the License.
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#include "pw_sync/spin_lock.h"
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#include "pw_assert/assert.h"
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#include "tx_api.h"
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namespace pw::sync {
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void SpinLock::lock() {
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// In order to be pw::sync::SpinLock compliant, mask the interrupts
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// before attempting to grab the internal spin lock.
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native_type_.saved_interrupt_mask = tx_interrupt_control(TX_INT_DISABLE);
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// This implementation is not set up to support SMP, meaning we cannot
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// deadlock here due to the global interrupt lock, so we crash on recursion
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// on a specific spinlock instead.
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PW_CHECK(!native_type_.locked.load(std::memory_order_relaxed),
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"Recursive SpinLock::lock() detected");
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native_type_.locked.store(true, std::memory_order_relaxed);
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}
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bool SpinLock::try_lock() {
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// In order to be pw::sync::SpinLock compliant, mask the interrupts
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// before attempting to grab the internal spin lock.
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UINT saved_interrupt_mask = tx_interrupt_control(TX_INT_DISABLE);
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if (native_type_.locked.load(std::memory_order_relaxed)) {
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// Already locked, restore interrupts and bail out.
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tx_interrupt_control(saved_interrupt_mask);
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return false;
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}
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native_type_.saved_interrupt_mask = saved_interrupt_mask;
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native_type_.locked.store(true, std::memory_order_relaxed);
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return true;
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}
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void SpinLock::unlock() {
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native_type_.locked.store(false, std::memory_order_relaxed);
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tx_interrupt_control(native_type_.saved_interrupt_mask);
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}
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} // namespace pw::sync
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