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
15 #include "pw_sync/interrupt_spin_lock.h"
16
17 #include "pw_assert/assert.h"
18 #include "pw_interrupt/context.h"
19 #include "task.h"
20
21 namespace pw::sync {
22
lock()23 void InterruptSpinLock::lock() {
24 if (interrupt::InInterruptContext()) {
25 native_type_.saved_interrupt_mask = taskENTER_CRITICAL_FROM_ISR();
26 } else { // Task context
27 taskENTER_CRITICAL();
28 }
29 // We can't deadlock here so crash instead.
30 PW_CHECK(!native_type_.locked.load(std::memory_order_relaxed),
31 "Recursive InterruptSpinLock::lock() detected");
32 native_type_.locked.store(true, std::memory_order_relaxed);
33 }
34
try_lock()35 bool InterruptSpinLock::try_lock() {
36 if (interrupt::InInterruptContext()) {
37 UBaseType_t saved_interrupt_mask = taskENTER_CRITICAL_FROM_ISR();
38 if (native_type_.locked.load(std::memory_order_relaxed)) {
39 // Already locked, restore interrupts and bail out.
40 taskEXIT_CRITICAL_FROM_ISR(saved_interrupt_mask);
41 return false;
42 }
43 native_type_.saved_interrupt_mask = saved_interrupt_mask;
44 } else { // Task context
45 taskENTER_CRITICAL();
46 if (native_type_.locked.load(std::memory_order_relaxed)) {
47 // ALready locked, restore interrupts and bail out.
48 taskEXIT_CRITICAL();
49 return false;
50 }
51 }
52 native_type_.locked.store(true, std::memory_order_relaxed);
53 return true;
54 }
55
unlock()56 void InterruptSpinLock::unlock() {
57 native_type_.locked.store(false, std::memory_order_relaxed);
58 if (interrupt::InInterruptContext()) {
59 taskEXIT_CRITICAL_FROM_ISR(native_type_.saved_interrupt_mask);
60 } else { // Task context
61 taskEXIT_CRITICAL();
62 }
63 }
64
65 } // namespace pw::sync
66