go.temporal.io/server@v1.23.0/common/locks/priority_mutex_impl.go (about)

     1  // The MIT License
     2  //
     3  // Copyright (c) 2020 Temporal Technologies Inc.  All rights reserved.
     4  //
     5  // Copyright (c) 2020 Uber Technologies, Inc.
     6  //
     7  // Permission is hereby granted, free of charge, to any person obtaining a copy
     8  // of this software and associated documentation files (the "Software"), to deal
     9  // in the Software without restriction, including without limitation the rights
    10  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    11  // copies of the Software, and to permit persons to whom the Software is
    12  // furnished to do so, subject to the following conditions:
    13  //
    14  // The above copyright notice and this permission notice shall be included in
    15  // all copies or substantial portions of the Software.
    16  //
    17  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    18  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    19  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    20  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    21  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    22  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    23  // THE SOFTWARE.
    24  
    25  package locks
    26  
    27  import (
    28  	"context"
    29  	"fmt"
    30  	"sync"
    31  )
    32  
    33  const (
    34  	PriorityMutexStateUnlocked     PriorityMutexState = 0
    35  	PriorityMutexStateLockedByHigh PriorityMutexState = 1
    36  	PriorityMutexStateLockedByLow  PriorityMutexState = 2
    37  )
    38  
    39  type (
    40  	PriorityMutexState int
    41  
    42  	PriorityMutexImpl struct {
    43  		locker   sync.Locker
    44  		highCV   ConditionVariable
    45  		lowCV    ConditionVariable
    46  		highWait int
    47  		lowWait  int
    48  
    49  		lockState PriorityMutexState
    50  	}
    51  )
    52  
    53  var _ PriorityMutex = (*PriorityMutexImpl)(nil)
    54  
    55  func NewPriorityMutex() *PriorityMutexImpl {
    56  	lock := &sync.Mutex{}
    57  	syncCV := NewConditionVariable(lock)
    58  	asyncCV := NewConditionVariable(lock)
    59  	return &PriorityMutexImpl{
    60  		locker:   lock,
    61  		highCV:   syncCV,
    62  		lowCV:    asyncCV,
    63  		highWait: 0,
    64  		lowWait:  0,
    65  
    66  		lockState: PriorityMutexStateUnlocked,
    67  	}
    68  }
    69  
    70  // LockHigh try to lock with high priority, use LockHigh / UnlockHigh pair to lock / unlock
    71  func (c *PriorityMutexImpl) LockHigh(
    72  	ctx context.Context,
    73  ) error {
    74  	c.locker.Lock()
    75  	defer c.locker.Unlock()
    76  
    77  	c.highWait += 1
    78  	defer func() { c.highWait -= 1 }()
    79  
    80  	for c.lockState != PriorityMutexStateUnlocked && ctx.Err() == nil {
    81  		c.highCV.Wait(ctx.Done())
    82  	}
    83  
    84  	if ctx.Err() != nil {
    85  		return ctx.Err()
    86  	}
    87  
    88  	c.lockState = PriorityMutexStateLockedByHigh
    89  	return nil
    90  }
    91  
    92  // LockLow try to lock with low priority, use LockLow / UnlockLow pair to lock / unlock
    93  func (c *PriorityMutexImpl) LockLow(
    94  	ctx context.Context,
    95  ) error {
    96  	c.locker.Lock()
    97  	defer c.locker.Unlock()
    98  
    99  	c.lowWait += 1
   100  	defer func() { c.lowWait -= 1 }()
   101  
   102  	for c.lockState != PriorityMutexStateUnlocked && ctx.Err() == nil {
   103  		c.lowCV.Wait(ctx.Done())
   104  	}
   105  
   106  	if ctx.Err() != nil {
   107  		return ctx.Err()
   108  	}
   109  
   110  	c.lockState = PriorityMutexStateLockedByLow
   111  	return nil
   112  }
   113  
   114  func (c *PriorityMutexImpl) TryLockHigh() bool {
   115  	c.locker.Lock()
   116  	defer c.locker.Unlock()
   117  
   118  	if c.lockState != PriorityMutexStateUnlocked {
   119  		return false
   120  	}
   121  
   122  	c.lockState = PriorityMutexStateLockedByHigh
   123  	return true
   124  }
   125  
   126  func (c *PriorityMutexImpl) TryLockLow() bool {
   127  	c.locker.Lock()
   128  	defer c.locker.Unlock()
   129  
   130  	if c.lockState != PriorityMutexStateUnlocked {
   131  		return false
   132  	}
   133  
   134  	c.lockState = PriorityMutexStateLockedByLow
   135  	return true
   136  }
   137  
   138  // UnlockHigh unlock with high priority, use LockHigh / UnlockHigh pair to lock / unlock
   139  func (c *PriorityMutexImpl) UnlockHigh() {
   140  	c.locker.Lock()
   141  	defer c.locker.Unlock()
   142  
   143  	if c.lockState != PriorityMutexStateLockedByHigh {
   144  		panic(fmt.Sprintf("unable to unlock high priority, state: %v\n", c.lockState))
   145  	}
   146  
   147  	c.lockState = PriorityMutexStateUnlocked
   148  	c.notify()
   149  }
   150  
   151  // UnlockLow unlock with low priority, use LockLow / UnlockLow pair to lock / unlock
   152  func (c *PriorityMutexImpl) UnlockLow() {
   153  	c.locker.Lock()
   154  	defer c.locker.Unlock()
   155  
   156  	if c.lockState != PriorityMutexStateLockedByLow {
   157  		panic(fmt.Sprintf("unable to unlock high priority, state: %v\n", c.lockState))
   158  	}
   159  
   160  	c.lockState = PriorityMutexStateUnlocked
   161  	c.notify()
   162  }
   163  
   164  func (c *PriorityMutexImpl) IsLocked() bool {
   165  	c.locker.Lock()
   166  	defer c.locker.Unlock()
   167  
   168  	return c.lockState != PriorityMutexStateUnlocked
   169  }
   170  
   171  func (c *PriorityMutexImpl) notify() {
   172  	if c.highWait > 0 {
   173  		c.highCV.Signal()
   174  	} else if c.lowWait > 0 {
   175  		c.lowCV.Signal()
   176  	}
   177  }