K 10
svn:author
V 3
jhb
K 8
svn:date
V 27
2004-07-09T17:46:27.000000Z
K 7
svn:log
V 524
Check the lock lists to see if they are empty directly rather than
assigning a pointer to the list and then dereferencing the pointer as a
second step.  When the first spin lock is acquired, curthread is not in
a critical section so it may be preempted and would end up using another
CPUs lock list instead of its own.

When this code was in witness_lock() this sequence was safe as curthread
was in a critical section already since witness_lock() is called after the
lock is acquired.

Tested by:	Daniel Lang dl at leo.org

END