The main difficulty is here is akin to a use-after-check race.
After you have done an Unlock, any other goroutine could have grabbed the
lock, so returning false does not mean the lock is available.
In fact it means nothing meaningful... unless you have otherwise guaranteed
no lock contention, right? And if you've already guaranteed no contention
by another mutex, why bother with this one?
If you expand on your larger goal, we might be able to suggest
an approach that avoids TryLock.
On Friday, January 2, 2026 at 11:42:24 PM UTC-3 John Souvestre wrote:
> Hi all.
>
>
>
> I have a question about the mutexes provided by the sync library. It is
> correct to say that using the 3 lines of code below, anywhere in Go code,
> won't have any effect, other than to introduce a slight, non-blocking delay
> while they execute? In other words, the mutex is guaranteed to be the same
> before and after, and won’t hang your code, regardless of what else is
> going on, including in other GoRoutines.
>
>
>
> // Note: x is a sync.Mutex.
>
> if x.TryLock() {
>
> // x was unlocked but is now locked by us.
>
> x.Unlock()
>
> }
>
>
>
> If so, then would these functions be non-blocking, correct, and safe to
> use?
>
>
>
> // Note: x will always be unlocked upon return.
>
> func TryUnlock(x *sync.Mutex) (success bool) {
>
> if x.TryLock() {
>
> // x was unlocked but is now locked by us.
>
> x.Unlock()
>
> return true
>
> }
>
> // x was unlocked to start with.
>
> return false
>
> }
>
>
>
> // Note: x will be the same (locked or unlocked) upon return.
>
> func IsLocked(x *sync.Mutex) (locked bool) {
>
> if x.TryLock() {
>
> // x was unlocked but is now locked by us.
>
> x.Unlock()
>
> return false
>
> }
>
> // x was locked to start with.
>
> return true
>
> }
>
>
>
> I do understand that what I'm trying to achieve here is ok to do in only
> rare cases. Indeed, I've only found a need for them and TryLock() on a few
> rare occasions.
>
>
>
> Thanks,
>
>
>
> John
>
>
>
> John Souvestre New Orleans LA, USA 504-454-0899
> <(504)%20454-0899>
>
>
>
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