K 10
svn:author
V 5
markj
K 8
svn:date
V 27
2017-02-16T23:05:20.819307Z
K 7
svn:log
V 671
Prevent CPU migration when checking the DTrace nofault flag on x86.

dtrace_trap() consumes page and protection faults triggered by code running
in DTrace probe context. Such faults occur with interrupts disabled and are
detected using a per-CPU flag. Regular faults cause dtrace_trap() to be
called with interrupts enabled, and nothing was ensuring that the flag was
read from the correct CPU. This may result in dtrace_trap() consuming
unrelated page and protection faults when DTrace is enabled, causing the
fault handler to return without actually having handled the fault.

Diagnosed by:	Ryan Libby <rlibby@gmail.com>
MFC after:	3 days
Sponsored by:	Dell EMC Isilon

END