What version of Go are you using (go version)?

go1.17.6

Does this issue reproduce with the latest release?

Reproduces on https://go.dev/play/p/5bfwPnkYyY3

What operating system and processor architecture are you using (go env)?

Have tried on darwin/amd64, linux/mips32, and whatever os/arch runs on Go Playground.

What did you do?

• Allocate a struct having a sync.Mutex and a *sync.Cond
• Allocate the sync.Cond, using a pointer to the mutex in the struct.
• Set a runtime finalizer on the struct, to see when it gets GC'ed
• Drop references to struct, call runtime.GC(), sleep... no finalizer is called.
• If you repeat the above, without initializing the sync.Cond or by setting x.cond = nil, the finalizer is called.

See the playgound for a sample: https://go.dev/play/p/5bfwPnkYyY3

I am currently using a workaround where I nilify the Cond in a struct when the associated struct is not pooled. I am using a custom pool, so I don't know if the above would be problematic for the GC when used with a sync.Pool that is purged.

What did you expect to see?

• Struct should have been GC'ed

What did you see instead?

• The opposite.