for now. This will prevent signals from waking them. Adjust
exit_lwps() to explicitly add LW_SINTR to all of them, so that
the process exit code can wake them up.
This is needed as threads in both of these wait channels die once
they are woken. So they aren't interruptable in the typical sense.
I am now able to suspend & resume firefox successfully now.
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.
walk the list, we're looking for a vp to do something with. We do
this in the signal code and in the timer code. The signal code already
runs with proc::p_lock held, so it's a very natural lock to use. The
timer code, however, calls into the sa timer code with a spinlock held.
Since proc::p_lock is an adaptable mutex, we can sleep to get it. Sleeping
with a spinlock is BAD. So proc::p_lock is _not_ the right lock there,
and something like sadata::sa_mutex would be best.
Address this difficulty by noting that both uses actually just read
the list. Changing the list of VPs is rare - once one's added, it stays
until the process ends. So make the locking protocol that to write the
list you have to hold both proc::p_lock and sadata::sa_mutex (taken
in that order). Thus holding either one individually grants read access.
This removes a case where we could sleep with timer_lock, a spinlock at
IPL_SCHED (!!), while trying to get p_lock. If that ever happened, we'd
pretty much be dead. So don't do that!
This fixes a merge botch from how I handled our gaining p_lock - p_lock
should not have simply replaced p_smutex.
While here, tweak the sa_unblock_userret() code for the case
when the blessed vp is actually running (on another CPU). Make its
resched RESCHED_IMMED so we whack the CPU. Addresses a hang I've
observed in starting firefox on occasion when I see one thread running
in userland and another thread sitting in lwpublk, which means it's on
the list of threads for which we need an unblocked upcall. This list is
one on which things should NOT linger.
christos