The Engine watchdog wrapped every wgengine.Engine method call in a
goroutine with a 45s timeout and crashed the process on timeout. It
was added years ago to surface deadlocks during development, but the
underlying deadlocks have long since been fixed, and even when it did
fire it produced obscure stack traces (from inside the watchdog
goroutine, not the original caller) without buying much.
Audit of userspaceEngine's methods shows none have cyclic locking or
unbounded blocking now that ResetAndStop no longer loops waiting for
DERPs to drain (fa49009ee). The watchdog is dead weight; remove it
along with the TS_DEBUG_DISABLE_WATCHDOG escape hatch.
Updates #19759
Change-Id: Iba9d718fe1f8718a6631296e336b138c31b99ff1
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Brad Fitzpatrick
2b338dd6a8