This eliminates a race between a successful Accept call and a
concurrent Close call, which previously could have shut down the
'run' goroutine before Accept sent to the newConns channel, causing
Accept to deadlock.
In fact, it eliminates the long-running 'run' goroutine entirely
(replacing it with a time.Timer), and in the process avoids leaking
O(N) closed connections when only the very first one is long-lived.
It also eliminates a potential double-Close bug: if the run method had
called l.wrapped.Close due to an idle timeout, a subsequent call to
Close would invoke l.wrapped.Close again. The io.Closer method
explicitly documents doubled Close calls as undefined behavior, and
many Closer implementations (especially test fakes) panic or deadlock
in that case.
It also eliminates a timer leak if the Listener rapidly oscillates
between active and idle: previously the implementation used
time.After, but it now uses an explicit time.Timer which can be
stopped (and garbage-collected) when the listener becomes active.
Idleness is now tracked based on the connection's Close method rather
than Read: we have no guarantee in general that a caller will ever
actually invoke Read (if, for example, they Close the connection as
soon as it is dialed), but we can reasonably expect a caller to at
least try to ensure that Close is always called.
We now also verify, using a finalizer on a best-effort basis, that the
Close method on each connection is called. We use the finalizer to
verify the Close call — rather than to close the connection implicitly
— because closing the connection in a finalizer would delay the start
of the idle timer by an arbitrary and unbounded duration after the
last connection is actually no longer in use.
Fixesgolang/go#46047.
Fixesgolang/go#51435.
For golang/go#46520.
For golang/go#49387.
Change-Id: If173a3ed7a44aff14734b72c8340122e8d020f26
Reviewed-on: https://go-review.googlesource.com/c/tools/+/388597
Run-TryBot: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Cottrell <iancottrell@google.com>
Auto-Submit: Bryan Mills <bcmills@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
Otherwise, the Await method on the corresponding AsyncCall will never
unblock, leading to a deadlock (detected by the test changes in
CL 388597).
For golang/go#46047
For golang/go#46520
For golang/go#49387
Change-Id: I7954f80786059772ddd7f8c98d8752d56d074919
Reviewed-on: https://go-review.googlesource.com/c/tools/+/388775
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Cottrell <iancottrell@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
Auto-Submit: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Bryan C. Mills
Ian Cottrell