| // 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. |
| |
| #include "pw_sync/interrupt_spin_lock.h" |
| |
| #include "pw_assert/check.h" |
| #include "pw_interrupt/context.h" |
| #include "tx_api.h" |
| |
| namespace pw::sync { |
| namespace { |
| |
| using State = backend::NativeInterruptSpinLock::State; |
| |
| } // namespace |
| |
| void InterruptSpinLock::lock() { |
| // In order to be pw::sync::InterruptSpinLock compliant, mask the interrupts |
| // before attempting to grab the internal spin lock. |
| native_type_.saved_interrupt_mask = tx_interrupt_control(TX_INT_DISABLE); |
| |
| const bool in_interrupt = interrupt::InInterruptContext(); |
| |
| // Disable thread switching to ensure kernel APIs cannot switch to other |
| // threads which could then end up deadlocking recursively on this same lock. |
| if (!in_interrupt) { |
| TX_THREAD* current_thread = tx_thread_identify(); |
| // During init, i.e. tx_application_define, there may not be a thread yet. |
| if (current_thread != nullptr) { |
| // Disable thread switching by raising the preemption threshold to the |
| // highest priority value of 0. |
| UINT preemption_success = tx_thread_preemption_change( |
| tx_thread_identify(), 0, &native_type_.saved_preemption_threshold); |
| PW_DCHECK_UINT_EQ( |
| TX_SUCCESS, preemption_success, "Failed to disable thread switching"); |
| } |
| } |
| |
| // This implementation is not set up to support SMP, meaning we cannot |
| // deadlock here due to the global interrupt lock, so we crash on recursion |
| // on a specific spinlock instead. |
| PW_CHECK_UINT_EQ(native_type_.state, |
| State::kUnlocked, |
| "Recursive InterruptSpinLock::lock() detected"); |
| |
| native_type_.state = |
| in_interrupt ? State::kLockedFromInterrupt : State::kLockedFromThread; |
| } |
| |
| bool InterruptSpinLock::try_lock() { |
| // In order to be pw::sync::InterruptSpinLock compliant, mask the interrupts |
| // before attempting to grab the internal spin lock. |
| const UINT saved_interrupt_mask = tx_interrupt_control(TX_INT_DISABLE); |
| |
| const bool in_interrupt = interrupt::InInterruptContext(); |
| |
| // Disable thread switching to ensure kernel APIs cannot switch to other |
| // threads which could then end up deadlocking recursively on this same lock. |
| if (!in_interrupt) { |
| TX_THREAD* current_thread = tx_thread_identify(); |
| // During init, i.e. tx_application_define, there may not be a thread yet. |
| if (current_thread != nullptr) { |
| // Disable thread switching by raising the preemption threshold to the |
| // highest priority value of 0. |
| UINT preemption_success = tx_thread_preemption_change( |
| tx_thread_identify(), 0, &native_type_.saved_preemption_threshold); |
| PW_DCHECK_UINT_EQ( |
| TX_SUCCESS, preemption_success, "Failed to disable thread switching"); |
| } |
| } |
| |
| if (native_type_.state != State::kUnlocked) { |
| // Already locked, restore interrupts and thread switching and bail out. |
| if (!interrupt::InInterruptContext()) { |
| // Restore thread switching. |
| UINT unused = 0; |
| UINT preemption_success = |
| tx_thread_preemption_change(tx_thread_identify(), |
| native_type_.saved_preemption_threshold, |
| &unused); |
| PW_DCHECK_UINT_EQ( |
| TX_SUCCESS, preemption_success, "Failed to restore thread switching"); |
| } |
| tx_interrupt_control(saved_interrupt_mask); |
| return false; |
| } |
| |
| native_type_.saved_interrupt_mask = saved_interrupt_mask; |
| native_type_.state = |
| in_interrupt ? State::kLockedFromInterrupt : State::kLockedFromThread; |
| return true; |
| } |
| |
| void InterruptSpinLock::unlock() { |
| const bool in_interrupt = interrupt::InInterruptContext(); |
| |
| const State expected_state = |
| in_interrupt ? State::kLockedFromInterrupt : State::kLockedFromThread; |
| PW_CHECK_UINT_EQ( |
| native_type_.state, |
| expected_state, |
| "InterruptSpinLock::unlock() was called from a different context " |
| "compared to the lock()"); |
| |
| native_type_.state = State::kUnlocked; |
| |
| if (!in_interrupt) { |
| TX_THREAD* current_thread = tx_thread_identify(); |
| // During init, i.e. tx_application_define, there may not be a thread yet. |
| if (current_thread != nullptr) { |
| // Restore thread switching. |
| UINT unused = 0; |
| UINT preemption_success = |
| tx_thread_preemption_change(tx_thread_identify(), |
| native_type_.saved_preemption_threshold, |
| &unused); |
| PW_DCHECK_UINT_EQ( |
| TX_SUCCESS, preemption_success, "Failed to restore thread switching"); |
| } |
| } |
| tx_interrupt_control(native_type_.saved_interrupt_mask); |
| } |
| |
| } // namespace pw::sync |