- Ditch the cross-CPU calibration stuff. It didn't work properly, and it's
near impossible to synchronize the CPUs in a running system, because bus
traffic will interfere with any calibration attempt, messing up the
timings.
- Only enable the TSC on CPUs where we are sure it does not drift. If we are
On a known good CPU, give the TSC high timecounter quality, making it the
default.
- When booting CPUs, detect TSC skew and account for it. Most Intel MP
systems have synchronized counters, but that need not be true if the
system has a complicated bus structure. As far as I know, AMD systems
do not have synchronized TSCs and so we need to handle skew.
- While an AP is waiting to be set running, try and make the TSC drift by
entering a reduced power state. If we detect drift, ensure that the TSC
does not get a high timecounter quality. This should not happen and is
only for safety.
- Make cpu_counter() stuff LKM safe.
Select the Xen idle routine for Xen, mwait if supported by the CPU and
it is not AMD and halt otherwise. As reported by Christoph Egger,
AMD Barcelona keeps the CPU in C0 state with MWAIT, contrary to HLT,
which uses C1 and therefore much less power.
doing the cmpxchg, where another thread can successfully get a read hold
on the lock. That shouldn't fail anyone trying trying to get a read
hold. So for read locks, never bail just because the CAS fails, only bail
if we the status bits in the lock word say we can't have it.
into the kernel. Based on a patch by jmcneill@, with many fixes and
improvements by me.
- Put MEMORY_DISK_DYNAMIC and MODULAR into the GENERIC kernels, so that
you can load miniroot.kmod from the boot blocks and boot into the
installer!
- I have seen one isolated panic in the x86 pmap, but otherwise i386
seems stable with preemption enabled.
- amd64 is missing the FPU handling changes and it's not yet safe to
enable it there.
- The usual level for kern.sched.kpreempt_pri will be 128 once enabled
by default. For testing, setting it to 0 helps to shake out bugs.
- Try to avoid mispredicted bracnhes in Xsyscall.
- Interrupts were being enabled in Xsyscall _after_ checking for ASTs,
while could have resulted in ugly behaviour like delayed signals or
context switches. Fix it.
DragonflyBSD uses the crit names for something quite different.
- Add a kpreempt_disabled function for diagnostic assertions.
- Add inline versions of kpreempt_enable/kpreempt_disable for primitives.
- Make some more changes for preemption safety to the x86 pmap.
we no longer need to guard against access from hardware interrupt handlers.
Additionally, if cloning a process with CLONE_SIGHAND, arrange to have the
child process share the parent's lock so that signal state may be kept in
sync. Partially addresses PR kern/37437.
Changes beyond OpenBSD's driver:
- Improved support for AMD K8
- Added support for AMD Barcelona, AMD Phenom and AMD Griffin
Tested on various single and multi-socket machines.
Review and OK xtreame
