(0) softint handler "handler A" is established
(1) CPU#X does softint_schedule() for "handler A"
- the softhand_t is set SOFTINT_PENDING flag
- the softhand_t is NOT set SOFTINT_ACTIVE flag yet
(2) CPU#X begins other H/W interrupt processing
(3) CPU#Y does softint_disestablish() for "handler A"
- waits until softhand_t's SOFTINT_ACTIVE of all CPUs is clear
- the softhand_t is set not SOFTINT_ACTIVE but SOFTINT_PENDING,
so CPU#Y does not wait
- unset the function of "handler A"
(4) CPU#X does softint_execute()
- the function of "handler A" is already clear, so panic
finishes (without blocking). Problem reported by hannken@, thanks!
- pserialize_read_enter: use splsoftserial(), not splsoftclock().
- pserialize_perform: add xcall(9) barrier as interrupts may be coalesced.
is to provide routines that do as KASSERT(9) says: append a message
to the panic format string when the assertion triggers, with optional
arguments.
Fix call sites to reflect the new definition.
Discussed on tech-kern@. See
http://mail-index.netbsd.org/tech-kern/2011/09/07/msg011427.html
Without it, on ports where splhigh() is inline, the compiler will optimise
the second SOFTINT_PENDING test in softint_schedule(). A dissasembly
of softint_schedule() with and without the volatile sh_flags confirm this
on sparc.
Because of this there is a race that could lead to the softhand_t
being enqueued twice on si_q, leading to a corrupted queue and
some handler being SOFTINT_PENDING but never called.
Should fix PR kern/38637
somewhere in the system. If it is, wait for it to complete before tearing
it down. The caller commits to not trigger the interrupt again once
disestablish is set in motion.
one of the following:
- Holding kernel_lock (indicating that the code is not MT safe).
- Bracketing critical sections with kpreempt_disable/kpreempt_enable.
- Holding the interrupt priority level above IPL_NONE.
Statistics on kernel preemption are reported via event counters, and
where preemption is deferred for some reason, it's also reported via
lockstat. The LWP priority at which preemption is triggered is tuneable
via sysctl.
- Socket layer becomes MP safe.
- Unix protocols become MP safe.
- Allows protocol processing interrupts to safely block on locks.
- Fixes a number of race conditions.
With much feedback from matt@ and plunky@.
- Reduce available SPL levels for hardware devices to none, vm, sched, high.
- Acquire kernel_lock only for interrupts at IPL_VM.
- Implement threaded soft interrupts.
tech-kern:
- Invert priority space so that zero is the lowest priority. Rearrange
number and type of priority levels into bands. Add new bands like
'kernel real time'.
- Ignore the priority level passed to tsleep. Compute priority for
sleep dynamically.
- For SCHED_4BSD, make priority adjustment per-LWP, not per-process.
For now these just pass through to the current softintr code.
(The naming is different to allow softint/softintr to co-exist for a while.
I'm hoping that should make it easier to transition.)
knakahara