1) Since we want to check for upcalls only once, take LW_SA_UPCALL
out of the while(l->l_flags & LW_USERRET) loop.
2) since the goal is to keep SA code out of userret() (and especially
all the emulations that include userret() but will never do SA),
ALWAYS set LW_SA_UPCALL when we set SAVP_FLAG_NOUPCALLS. Drop the
test for it in lwp_userret() since it will never be set bare.
3) Adapt sa_upcall_userret() to clear LW_SA_UPCALL if it's no longer
needed. If we have gained upcalls since sa_yield(), we will deliver
them next time around.
Tested by skrll at.
- Change minimal time-quantum to ~20 ms.
- Thus remove unneeded pool in M2, and unused sched_lwp_exit().
- Do not increase l_slptime twice for SCHED_4BSD (regression fix).
mi_switch(), migration for LSONPROC is now performed via idle loop.
Handles/fixes on-CPU case in lwp_migrate(), misc.
Closes PR/38169, idea of migration via idle loop by Andrew Doran.
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.
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.
proclist_mutex and proclist_lock into a single adaptive mutex (proc_lock).
Implications:
- Inspecting process state requires thread context, so signals can no longer
be sent from a hardware interrupt handler. Signal activity must be
deferred to a soft interrupt or kthread.
- As the proc state locking is simplified, it's now safe to take exit()
and wait() out from under kernel_lock.
- The system spends less time at IPL_SCHED, and there is less lock activity.
existing behaviour: the unsleep method unlocks and wakes the swapper if
needs be. If false, the caller is doing a batch operation and will take
care of that later. This is kind of ugly, but it's difficult for the caller
to know which lock to release in some situations.
Add schedctl(8) - a program to control scheduling of processes and threads.
Notes:
- This is supported only by SCHED_M2;
- Migration of LWP mechanism will be revisited;
Proposed on: <tech-kern>. Reviewed by: <ad>.
context switch, since cpu_switchto() can be slow under certain conditions.
From rmind@ with adjustments by me.
- lwpctl: allow LWPs to reregister instead of returning EINVAL. Just return
their existing lwpctl user address.
