Remove default impl of assert_havelock; add ::SpinLock impl

Author: NHDaly

base/condition.jl

@@ -22,7 +22,6 @@ function trylock end
 function islocked end
 unlockall(l::AbstractLock) = unlock(l) # internal function for implementing `wait`
 relockall(l::AbstractLock, token::Nothing) = lock(l) # internal function for implementing `wait`
-assert_havelock(l::AbstractLock) = assert_havelock(l, Threads.threadid())
 assert_havelock(l::AbstractLock, tid::Integer) =
     (islocked(l) && tid == Threads.threadid()) ? nothing : concurrency_violation()
 assert_havelock(l::AbstractLock, tid::Task) =

base/locks-mt.jl

@@ -30,6 +30,10 @@ struct SpinLock <: AbstractLock
     SpinLock() = new(Atomic{Int}(0))
 end
 
+# Note: this cannot assert that the lock is held by the correct thread, because we do not
+# track which thread locked it. Users beware.
+Base.assert_havelock(l::SpinLock) = islocked(l) ? nothing : concurrency_violation()
+
 function lock(l::SpinLock)
     while true
         if l.handle[] == 0