Documentation
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Overview ¶
Package motex implements a demoteable and promoteable exclusion lock. Demoteable meaning a write lock can be changed to a read lock. Promoteable meaning a demoted write lock can be changed back to a write lock.
If Demote() and Promote() are never called, motex behaves identically to a sync.RWMutex.
A demoted lock continues to block calls to Lock, but calls to RLock will not block.
non-atomic read and update with sync.Mutex:
var mu sync.Mutex var state int mu.RLock() copied := state mu.RUnlock() copied += 1 // ... do something resource intensive to modify the copied state. mu.Lock() state = copied mu.Unlock()
atomic read and update with motex.Motex:
var mo motex.Motex var state int mo.Lock() mo.Demote() copied := state copied += 1 // ... do something resource intensive to modiy the copied state. mo.Promote() state = copied mo.Unlock()
Index ¶
Constants ¶
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Variables ¶
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Functions ¶
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Types ¶
type Motex ¶
type Motex struct {
// contains filtered or unexported fields
}
A Motex is a demoteable and promoteable exclusion lock.
A Motex must not be copied after first use.
func (*Motex) Demote ¶
func (m *Motex) Demote()
Demote demotes m from a Lock() for writing to a lock for reading, unblocking any calls to RLock. Other calls to Lock will continue to block. It is a run-time error if m is not currently locked for writing. It is also a run-time error if m is locked for writing but demoted on entry to Demote.
A demoted lock is not equivalent to an RLock. Only demoted locks can be promoted.
func (*Motex) Lock ¶
func (m *Motex) Lock()
Lock locks m for writing. If the lock is already locked for reading or writing, Lock blocks until the lock is available (i.e. after Unlock or RUnlock is called).
func (*Motex) Promote ¶
func (m *Motex) Promote()
Promote promotes m from a Demoted() Lock() to a lock for writing, blocking all calls to RLock. If the lock is already RLocked, Promote blocks until the lock is available (i.e. after RUnlock is called). It is a run-time error if m is not currently a demoted lock.
A demoted lock is not equivalent to an RLock. Only demoted locks can be promoted.
func (*Motex) RLock ¶
func (m *Motex) RLock()
RLock locks m for reading. If the lock is already locked for writing or demoted reading, RLock blocks until the lock is available (i.e. after Unlock is called).
Source Files