Struct spin::rwlock::RwLockUpgradableGuard [−][src]
Expand description
A guard that provides immutable data access but can be upgraded to RwLockWriteGuard.
No writers or other upgradeable guards can exist while this is in scope. New reader creation is prevented (to alleviate writer starvation) but there may be existing readers when the lock is acquired.
When the guard falls out of scope it will release the lock.
Implementations
Upgrades an upgradeable lock guard to a writable lock guard.
let mylock = spin::RwLock::new(0); let upgradeable = mylock.upgradeable_read(); // Readable, but not yet writable let writable = upgradeable.upgrade();
Tries to upgrade an upgradeable lock guard to a writable lock guard.
let mylock = spin::RwLock::new(0); let upgradeable = mylock.upgradeable_read(); // Readable, but not yet writable match upgradeable.try_upgrade() { Ok(writable) => /* upgrade successful - use writable lock guard */ (), Err(upgradeable) => /* upgrade unsuccessful */ (), };
Downgrades the upgradeable lock guard to a readable, shared lock guard. Cannot fail and is guaranteed not to spin.
let mylock = spin::RwLock::new(1); let upgradeable = mylock.upgradeable_read(); assert!(mylock.try_read().is_none()); assert_eq!(*upgradeable, 1); let readable = upgradeable.downgrade(); // This is guaranteed not to spin assert!(mylock.try_read().is_some()); assert_eq!(*readable, 1);
Leak the lock guard, yielding a reference to the underlying data.
Note that this function will permanently lock the original lock.
let mylock = spin::RwLock::new(0); let data: &i32 = spin::RwLockUpgradableGuard::leak(mylock.upgradeable_read()); assert_eq!(*data, 0);