TheArchive/tailscale
1
0
Fork 0
mirror of https://github.com/tailscale/tailscale.git synced 2025-08-13 14:43:19 +00:00
Code Issues Packages Projects Releases Wiki Activity

syncs: fix AtomicValue.CompareAndSwap (#16137)

Browse Source 
Fix CompareAndSwap in the edge-case where
the underlying sync.AtomicValue is uninitialized
(i.e., Store was never called) and
the oldV is the zero value,
then perform CompareAndSwap with any(nil).

Also, document that T must be comparable.
This is a pre-existing restriction.

Fixes #16135

Signed-off-by: Joe Tsai <joetsai@digital-static.net>
This commit is contained in:
Joe Tsai
2025-05-30 08:06:16 -10:00
committed by GitHub
parent 11e83f9da5
commit 84aa7ff3bb
2 changed files with 25 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
syncs/syncs.go
View File

@@ -67,12 +67,18 @@ func (v *AtomicValue[T]) Swap(x T) (old T) {
if oldV != nil {
return oldV.(wrappedValue[T]).v
}
return old
return old // zero value of T
}
// CompareAndSwap executes the compare-and-swap operation for the Value.
// It panics if T is not comparable.
func (v *AtomicValue[T]) CompareAndSwap(oldV, newV T) (swapped bool) {
return v.v.CompareAndSwap(wrappedValue[T]{oldV}, wrappedValue[T]{newV})
var zero T
return v.v.CompareAndSwap(wrappedValue[T]{oldV}, wrappedValue[T]{newV}) ||
// In the edge-case where [atomic.Value.Store] is uninitialized
// and trying to compare with the zero value of T,
// then compare-and-swap with the nil any value.
(any(oldV) == any(zero) && v.v.CompareAndSwap(any(nil), wrappedValue[T]{newV}))
}
// MutexValue is a value protected by a mutex.