kern/src/schedule.c

/* Copyright (c) 2009, 2012 The Regents of the University of California
 * Barret Rhoden <brho@cs.berkeley.edu>
 * See LICENSE for details.
 *
 * Scheduling and dispatching. */

#include <schedule.h>
#include <corerequest.h>
#include <process.h>
#include <monitor.h>
#include <stdio.h>
#include <assert.h>
#include <atomic.h>
#include <smp.h>
#include <manager.h>
#include <alarm.h>
#include <sys/queue.h>
#include <arsc_server.h>
#include <hashtable.h>

/* Process Lists.  'unrunnable' is a holding list for SCPs that are running or
 * waiting or otherwise not considered for sched decisions. */
struct proc_list unrunnable_scps = TAILQ_HEAD_INITIALIZER(unrunnable_scps);
struct proc_list runnable_scps = TAILQ_HEAD_INITIALIZER(runnable_scps);
/* mcp lists.  we actually could get by with one list and a TAILQ_CONCAT, but
 * I'm expecting to want the flexibility of the pointers later. */
struct proc_list all_mcps_1 = TAILQ_HEAD_INITIALIZER(all_mcps_1);
struct proc_list all_mcps_2 = TAILQ_HEAD_INITIALIZER(all_mcps_2);
struct proc_list *primary_mcps = &all_mcps_1;
struct proc_list *secondary_mcps = &all_mcps_2;

/* Helper, defined below */
static void __core_request(struct proc *p, uint32_t amt_needed);
static void add_to_list(struct proc *p, struct proc_list *list);
static void remove_from_list(struct proc *p, struct proc_list *list);
static void switch_lists(struct proc *p, struct proc_list *old,
                         struct proc_list *new);
static void __run_mcp_ksched(void *arg);	/* don't call directly */
static uint32_t get_cores_needed(struct proc *p);

/* Locks / sync tools */

/* poke-style ksched - ensures the MCP ksched only runs once at a time.  since
 * only one mcp ksched runs at a time, while this is set, the ksched knows no
 * cores are being allocated by other code (though they could be dealloc, due to
 * yield).
 *
 * The main value to this sync method is to make the 'make sure the ksched runs
 * only once at a time and that it actually runs' invariant/desire wait-free, so
 * that it can be called anywhere (deep event code, etc).
 *
 * As the ksched gets smarter, we'll probably embedd this poker in a bigger
 * struct that can handle the posting of different types of work. */
struct poke_tracker ksched_poker = POKE_INITIALIZER(__run_mcp_ksched);

/* this 'big ksched lock' protects a bunch of things, which i may make fine
 * grained: */
/* - protects the integrity of proc tailqs/structures, as well as the membership
 * of a proc on those lists.  proc lifetime within the ksched but outside this
 * lock is protected by the proc kref. */
//spinlock_t proclist_lock = SPINLOCK_INITIALIZER; /* subsumed by bksl */
/* - protects the provisioning assignment, and the integrity of all prov
 * lists (the lists of each proc). */
//spinlock_t prov_lock = SPINLOCK_INITIALIZER;
/* - protects allocation structures */
//spinlock_t alloc_lock = SPINLOCK_INITIALIZER;
spinlock_t sched_lock = SPINLOCK_INITIALIZER;

/* Alarm struct, for our example 'timer tick' */
struct alarm_waiter ksched_waiter;

#define TIMER_TICK_USEC 10000 	/* 10msec */

/* Helper: Sets up a timer tick on the calling core to go off 10 msec from now.
 * This assumes the calling core is an LL core, etc. */
static void set_ksched_alarm(void)
{
	set_awaiter_rel(&ksched_waiter, TIMER_TICK_USEC);
	set_alarm(&per_cpu_info[core_id()].tchain, &ksched_waiter);
}

/* RKM alarm, to run the scheduler tick (not in interrupt context) and reset the
 * alarm.  Note that interrupts will be disabled, but this is not the same as
 * interrupt context.  We're a routine kmsg, which means the core is in a
 * quiescent state. */
static void __ksched_tick(struct alarm_waiter *waiter)
{
	/* TODO: imagine doing some accounting here */
	run_scheduler();
	/* Set our alarm to go off, relative to now.  This means we might lag a
	 * bit, and our ticks won't match wall clock time.  But if we do
	 * incremental, we'll actually punish the next process because the
	 * kernel took too long for the previous process.  Ultimately, if we
	 * really care, we should account for the actual time used. */
	set_awaiter_rel(&ksched_waiter, TIMER_TICK_USEC);
	set_alarm(&per_cpu_info[core_id()].tchain, &ksched_waiter);
}

void schedule_init(void)
{
	spin_lock(&sched_lock);
	assert(!core_id());		/* want the alarm on core0 for now */
	init_awaiter(&ksched_waiter, __ksched_tick);
	set_ksched_alarm();
	corealloc_init();
	spin_unlock(&sched_lock);

#ifdef CONFIG_ARSC_SERVER
	/* Most likely we'll have a syscall and a process that dedicates itself
	 * to running this.  Or if it's a kthread, we don't need a core. */
	#error "Find a way to get a core.  Probably a syscall to run a server."
	int arsc_coreid = get_any_idle_core();
	assert(arsc_coreid >= 0);
	send_kernel_message(arsc_coreid, arsc_server, 0, 0, 0, KMSG_ROUTINE);
	printk("Using core %d for the ARSC server\n", arsc_coreid);
#endif /* CONFIG_ARSC_SERVER */
}

/* Round-robins on whatever list it's on */
static void add_to_list(struct proc *p, struct proc_list *new)
{
	assert(!(p->ksched_data.cur_list));
	TAILQ_INSERT_TAIL(new, p, ksched_data.proc_link);
	p->ksched_data.cur_list = new;
}

static void remove_from_list(struct proc *p, struct proc_list *old)
{
	assert(p->ksched_data.cur_list == old);
	TAILQ_REMOVE(old, p, ksched_data.proc_link);
	p->ksched_data.cur_list = 0;
}

static void switch_lists(struct proc *p, struct proc_list *old,
                         struct proc_list *new)
{
	remove_from_list(p, old);
	add_to_list(p, new);
}

/* Removes from whatever list p is on */
static void remove_from_any_list(struct proc *p)
{
	if (p->ksched_data.cur_list) {
		TAILQ_REMOVE(p->ksched_data.cur_list, p, ksched_data.proc_link);
		p->ksched_data.cur_list = 0;
	}
}

/************** Process Management Callbacks **************/
/* a couple notes:
 * - the proc lock is NOT held for any of these calls.  currently, there is no
 *   lock ordering between the sched lock and the proc lock.  since the proc
 *   code doesn't know what we do, it doesn't hold its lock when calling our
 *   CBs.
 * - since the proc lock isn't held, the proc could be dying, which means we
 *   will receive a __sched_proc_destroy() either before or after some of these
 *   other CBs.  the CBs related to list management need to check and abort if
 *   DYING */
void __sched_proc_register(struct proc *p)
{
	assert(!proc_is_dying(p));
	/* one ref for the proc's existence, cradle-to-grave */
	proc_incref(p, 1); /* need at least this OR the 'one for existing' */
	spin_lock(&sched_lock);
	corealloc_proc_init(p);
	add_to_list(p, &unrunnable_scps);
	spin_unlock(&sched_lock);
}

/* Returns 0 if it succeeded, an error code otherwise. */
void __sched_proc_change_to_m(struct proc *p)
{
	spin_lock(&sched_lock);
	/* Need to make sure they aren't dying.  if so, we already dealt with
	 * their list membership, etc (or soon will).  taking advantage of the
	 * 'immutable state' of dying (so long as refs are held). */
	if (proc_is_dying(p)) {
		spin_unlock(&sched_lock);
		return;
	}
	/* Catch user bugs */
	if (!p->procdata->res_req[RES_CORES].amt_wanted) {
		printk("[kernel] process needs to specify amt_wanted\n");
		p->procdata->res_req[RES_CORES].amt_wanted = 1;
	}
	/* For now, this should only ever be called on an unrunnable.  It's
	 * probably a bug, at this stage in development, to do o/w. */
	remove_from_list(p, &unrunnable_scps);
	//remove_from_any_list(p); 	/* ^^ instead of this */
	add_to_list(p, primary_mcps);
	spin_unlock(&sched_lock);
	//poke_ksched(p, RES_CORES);
}

/* Sched callback called when the proc dies.  pc_arr holds the cores the proc
 * had, if any, and nr_cores tells us how many are in the array.
 *
 * An external, edible ref is passed in.  when we return and they decref,
 * __proc_free will be called (when the last one is done). */
void __sched_proc_destroy(struct proc *p, uint32_t *pc_arr, uint32_t nr_cores)
{
	spin_lock(&sched_lock);
	/* Unprovision any cores.  Note this is different than
	 * track_core_dealloc.  The latter does bookkeeping when an allocation
	 * changes.  This is a bulk *provisioning* change. */
	__unprovision_all_cores(p);
	/* Remove from whatever list we are on (if any - might not be on one if
	 * it was in the middle of __run_mcp_sched) */
	remove_from_any_list(p);
	if (nr_cores)
		__track_core_dealloc_bulk(p, pc_arr, nr_cores);
	spin_unlock(&sched_lock);
	/* Drop the cradle-to-the-grave reference, jet-li */
	proc_decref(p);
}

/* ksched callbacks.  p just woke up and is UNLOCKED. */
void __sched_mcp_wakeup(struct proc *p)
{
	spin_lock(&sched_lock);
	if (proc_is_dying(p)) {
		spin_unlock(&sched_lock);
		return;
	}
	/* could try and prioritize p somehow (move it to the front of the
	 * list). */
	spin_unlock(&sched_lock);
	/* note they could be dying at this point too. */
	poke(&ksched_poker, p);
}

/* ksched callbacks.  p just woke up and is UNLOCKED. */
void __sched_scp_wakeup(struct proc *p)
{
	spin_lock(&sched_lock);
	if (proc_is_dying(p)) {
		spin_unlock(&sched_lock);
		return;
	}
	/* might not be on a list if it is new.  o/w, it should be unrunnable */
	remove_from_any_list(p);
	add_to_list(p, &runnable_scps);
	spin_unlock(&sched_lock);
	/* we could be on a CG core, and all the mgmt cores could be halted.  if
	 * we don't tell one of them about the new proc, they will sleep until
	 * the timer tick goes off. */
	if (!management_core()) {
		/* TODO: pick a better core and only send if halted.
		 *
		 * ideally, we'd know if a specific mgmt core is sleeping and
		 * wake it up.  o/w, we could interrupt an already-running mgmt
		 * core that won't get to our new proc anytime soon.  also, by
		 * poking core 0, a different mgmt core could remain idle (and
		 * this process would sleep) until its tick goes off */
		send_ipi(0, I_POKE_CORE);
	}
}

/* Callback to return a core to the ksched, which tracks it as idle and
 * deallocated from p.  The proclock is held (__core_req depends on that).
 *
 * This also is a trigger, telling us we have more cores.  We could/should make
 * a scheduling decision (or at least plan to). */
void __sched_put_idle_core(struct proc *p, uint32_t coreid)
{
	spin_lock(&sched_lock);
	__track_core_dealloc(p, coreid);
	spin_unlock(&sched_lock);
}

/* Callback, bulk interface for put_idle. The proclock is held for this. */
void __sched_put_idle_cores(struct proc *p, uint32_t *pc_arr, uint32_t num)
{
	spin_lock(&sched_lock);
	__track_core_dealloc_bulk(p, pc_arr, num);
	spin_unlock(&sched_lock);
	/* could trigger a sched decision here */
}

/* mgmt/LL cores should call this to schedule the calling core and give it to an
 * SCP.  will also prune the dead SCPs from the list.  hold the lock before
 * calling.  returns TRUE if it scheduled a proc. */
static bool __schedule_scp(void)
{
	// TODO: sort out lock ordering (proc_run_s also locks)
	struct proc *p;
	uint32_t pcoreid = core_id();
	struct per_cpu_info *pcpui = &per_cpu_info[pcoreid];

	/* if there are any runnables, run them here and put any currently
	 * running SCP on the tail of the runnable queue. */
	if ((p = TAILQ_FIRST(&runnable_scps))) {
		/* someone is currently running, dequeue them */
		if (pcpui->owning_proc) {
			spin_lock(&pcpui->owning_proc->proc_lock);
			/* process might be dying, with a KMSG to clean it up
			 * waiting on this core.  can't do much, so we'll
			 * attempt to restart */
			if (proc_is_dying(pcpui->owning_proc)) {
				run_as_rkm(run_scheduler);
				spin_unlock(&pcpui->owning_proc->proc_lock);
				return FALSE;
			}
			printd("Descheduled %d in favor of %d\n",
			       pcpui->owning_proc->pid, p->pid);
			__proc_set_state(pcpui->owning_proc, PROC_RUNNABLE_S);
			/* Saving FP state aggressively.  Odds are, the SCP was
			 * hit by an IRQ and has a HW ctx, in which case we must
			 * save. */
			__proc_save_fpu_s(pcpui->owning_proc);
			__proc_save_context_s(pcpui->owning_proc);
			vcore_account_offline(pcpui->owning_proc, 0);
			__seq_start_write(&p->procinfo->coremap_seqctr);
			__unmap_vcore(p, 0);
			__seq_end_write(&p->procinfo->coremap_seqctr);
			spin_unlock(&pcpui->owning_proc->proc_lock);
			/* round-robin the SCPs (inserts at the end of the
			 * queue) */
			switch_lists(pcpui->owning_proc, &unrunnable_scps,
				     &runnable_scps);
			clear_owning_proc(pcoreid);
			/* Note we abandon core.  It's not strictly necessary.
			 * If we didn't, the TLB would still be loaded with the
			 * old one, til we proc_run_s, and the various paths in
			 * proc_run_s would pick it up.  This way is a bit safer
			 * for future changes, but has an extra (empty) TLB
			 * flush.  */
			abandon_core();
		}
		/* Run the new proc */
		switch_lists(p, &runnable_scps, &unrunnable_scps);
		printd("PID of the SCP i'm running: %d\n", p->pid);
		proc_run_s(p);	/* gives it core we're running on */
		return TRUE;
	}
	return FALSE;
}

/* Returns how many new cores p needs.  This doesn't lock the proc, so your
 * answer might be stale. */
static uint32_t get_cores_needed(struct proc *p)
{
	uint32_t amt_wanted, amt_granted;

	amt_wanted = p->procdata->res_req[RES_CORES].amt_wanted;
	/* Help them out - if they ask for something impossible, give them 1 so
	 * they can make some progress. (this is racy, and unnecessary). */
	if (amt_wanted > p->procinfo->max_vcores) {
		printk("[kernel] proc %d wanted more than max, wanted %d\n",
		       p->pid, amt_wanted);
		p->procdata->res_req[RES_CORES].amt_wanted = 1;
		amt_wanted = 1;
	}
	/* There are a few cases where amt_wanted is 0, but they are still
	 * RUNNABLE (involving yields, events, and preemptions).  In these
	 * cases, give them at least 1, so they can make progress and yield
	 * properly.  If they are not WAITING, they did not yield and may have
	 * missed a message. */
	if (!amt_wanted) {
		/* could ++, but there could be a race and we don't want to give
		 * them more than they ever asked for (in case they haven't
		 * prepped) */
		p->procdata->res_req[RES_CORES].amt_wanted = 1;
		amt_wanted = 1;
	}
	/* amt_granted is racy - they could be *yielding*, but currently they
	 * can't be getting any new cores if the caller is in the mcp_ksched.
	 * this is okay - we won't accidentally give them more cores than they
	 * *ever* wanted (which could crash them), but our answer might be a
	 * little stale. */
	amt_granted = p->procinfo->res_grant[RES_CORES];
	/* Do not do an assert like this: it could fail (yield in progress): */
	//assert(amt_granted == p->procinfo->num_vcores);
	if (amt_wanted <= amt_granted)
		return 0;
	return amt_wanted - amt_granted;
}

/* Actual work of the MCP kscheduler.  if we were called by poke_ksched, *arg
 * might be the process who wanted special service.  this would be the case if
 * we weren't already running the ksched.  Sort of a ghetto way to "post work",
 * such that it's an optimization. */
static void __run_mcp_ksched(void *arg)
{
	struct proc *p, *temp;
	uint32_t amt_needed;
	struct proc_list *temp_mcp_list;

	/* locking to protect the MCP lists' integrity and membership */
	spin_lock(&sched_lock);
	/* 2-pass scheme: check each proc on the primary list (FCFS).  if they
	 * need nothing, put them on the secondary list.  if they need
	 * something, rip them off the list, service them, and if they are still
	 * not dying, put them on the secondary list.  We cull the entire
	 * primary list, so that when we start from the beginning each time, we
	 * aren't repeatedly checking procs we looked at on previous waves.
	 *
	 * TODO: we could modify this such that procs that we failed to service
	 * move to yet another list or something.  We can also move the WAITINGs
	 * to another list and have wakeup move them back, etc. */
	while (!TAILQ_EMPTY(primary_mcps)) {
		TAILQ_FOREACH_SAFE(p, primary_mcps, ksched_data.proc_link, temp)
		{
			/* unlocked peek at the state */
			if (p->state == PROC_WAITING) {
				switch_lists(p, primary_mcps, secondary_mcps);
				continue;
			}
			amt_needed = get_cores_needed(p);
			if (!amt_needed) {
				switch_lists(p, primary_mcps, secondary_mcps);
				continue;
			}
			/* o/w, we want to give cores to this proc */
			remove_from_list(p, primary_mcps);
			/* now it won't die, but it could get removed from lists
			 * and have its stuff unprov'd when we unlock */
			proc_incref(p, 1);
			/* GIANT WARNING: __core_req will unlock the sched lock
			 * for a bit.  It will return with it locked still.  We
			 * could unlock before we pass in, but they will relock
			 * right away. */
			/* for mouse-eyed viewers */
			// notionally_unlock(&ksched_lock);
			__core_request(p, amt_needed);
			// notionally_lock(&ksched_lock);
			/* Peeking at the state is okay, since we hold a ref.
			 * Once it is DYING, it'll remain DYING until we decref.
			 * And if there is a concurrent death, that will spin on
			 * the ksched lock (which we hold, and which protects
			 * the proc lists). */
			if (!proc_is_dying(p))
				add_to_list(p, secondary_mcps);
			proc_decref(p);	/* fyi, this may trigger __proc_free */
			/* need to break: the proc lists may have changed when
			 * we unlocked in core_req in ways that the FOREACH_SAFE
			 * can't handle. */
			break;
		}
	}
	/* at this point, we moved all the procs over to the secondary list, and
	 * attempted to service the ones that wanted something.  now just swap
	 * the lists for the next invocation of the ksched. */
	temp_mcp_list = primary_mcps;
	primary_mcps = secondary_mcps;
	secondary_mcps = temp_mcp_list;
	spin_unlock(&sched_lock);
}

/* Something has changed, and for whatever reason the scheduler should
 * reevaluate things.
 *
 * Don't call this if you are processing a syscall or otherwise care about your
 * kthread variables, cur_proc/owning_proc, etc.
 *
 * Don't call this from interrupt context (grabs proclocks). */
void run_scheduler(void)
{
	/* MCP scheduling: post work, then poke.  for now, i just want the func
	 * to run again, so merely a poke is sufficient. */
	poke(&ksched_poker, 0);
	if (management_core()) {
		spin_lock(&sched_lock);
		__schedule_scp();
		spin_unlock(&sched_lock);
	}
}

/* A process is asking the ksched to look at its resource desires.  The
 * scheduler is free to ignore this, for its own reasons, so long as it
 * eventually gets around to looking at resource desires. */
void poke_ksched(struct proc *p, unsigned int res_type)
{
	/* ignoring res_type for now.  could post that if we wanted (would need
	 * some other structs/flags) */
	if (!__proc_is_mcp(p))
		return;
	poke(&ksched_poker, p);
}

/* The calling cpu/core has nothing to do and plans to idle/halt.  This is an
 * opportunity to pick the nature of that halting (low power state, etc), or
 * provide some other work (_Ss on LL cores).  Note that interrupts are
 * disabled, and if you return, the core will cpu_halt(). */
void cpu_bored(void)
{
	bool new_proc = FALSE;
	if (!management_core())
		return;
	spin_lock(&sched_lock);
	new_proc = __schedule_scp();
	spin_unlock(&sched_lock);
	/* if we just scheduled a proc, we need to manually restart it, instead
	 * of returning.  if we return, the core will halt. */
	if (new_proc) {
		proc_restartcore();
		assert(0);
	}
	/* Could drop into the monitor if there are no processes at all.  For
	 * now, the 'call of the giraffe' suffices. */
}

/* Available resources changed (plus or minus).  Some parts of the kernel may
 * call this if a particular resource that is 'quantity-based' changes.  Things
 * like available RAM to processes, bandwidth, etc.  Cores would probably be
 * inappropriate, since we need to know which specific core is now free. */
void avail_res_changed(int res_type, long change)
{
	printk("[kernel] ksched doesn't track any resources yet!\n");
}

/* This deals with a request for more cores.  The amt of new cores needed is
 * passed in.  The ksched lock is held, but we are free to unlock if we want
 * (and we must, if calling out of the ksched to anything high-level).
 *
 * Side note: if we want to warn, then we can't deal with this proc's prov'd
 * cores until we wait til the alarm goes off.  would need to put all
 * alarmed cores on a list and wait til the alarm goes off to do the full
 * preempt.  and when those cores come in voluntarily, we'd need to know to
 * give them to this proc. */
static void __core_request(struct proc *p, uint32_t amt_needed)
{
	uint32_t nr_to_grant = 0;
	uint32_t corelist[num_cores];
	uint32_t pcoreid;
	struct proc *proc_to_preempt;
	bool success;

	/* we come in holding the ksched lock, and we hold it here to protect
	 * allocations and provisioning. */
	/* get all available cores from their prov_not_alloc list.  the list
	 * might change when we unlock (new cores added to it, or the entire
	 * list emptied, but no core allocations will happen (we hold the
	 * poke)). */
	while (nr_to_grant != amt_needed) {
		/* Find the next best core to allocate to p. It may be a core
		 * provisioned to p, and it might not be. */
		pcoreid = __find_best_core_to_alloc(p);
		/* If no core is returned, we know that there are no more cores
		 * to give out, so we exit the loop. */
		if (pcoreid == -1)
			break;
		/* If the pcore chosen currently has a proc allocated to it, we
		 * know it must be provisioned to p, but not allocated to it. We
		 * need to try to preempt. After this block, the core will be
		 * track_dealloc'd and on the idle list (regardless of whether
		 * we had to preempt or not) */
		if (get_alloc_proc(pcoreid)) {
			proc_to_preempt = get_alloc_proc(pcoreid);
			/* would break both preemption and maybe the later
			 * decref */
			assert(proc_to_preempt != p);
			/* need to keep a valid, external ref when we unlock */
			proc_incref(proc_to_preempt, 1);
			spin_unlock(&sched_lock);
			/* sending no warning time for now - just an immediate
			 * preempt. */
			success = proc_preempt_core(proc_to_preempt, pcoreid,
						    0);
			/* reaquire locks to protect provisioning and idle lists
			 */
			spin_lock(&sched_lock);
			if (success) {
				/* we preempted it before the proc could yield
				 * or die.  alloc_proc should not have changed
				 * (it'll change in death and idle CBs).  the
				 * core is not on the idle core list.  (if we
				 * ever have proc alloc lists, it'll still be on
				 * the old proc's list). */
				assert(get_alloc_proc(pcoreid));
				/* regardless of whether or not it is still prov
				 * to p, we need to note its dealloc.  we are
				 * doing some excessive checking of p ==
				 * prov_proc, but using this helper is a lot
				 * clearer. */
				__track_core_dealloc(proc_to_preempt, pcoreid);
			} else {
				/* the preempt failed, which should only happen
				 * if the pcore was unmapped (could be dying,
				 * could be yielding, but NOT preempted).
				 * whoever unmapped it also triggered (or will
				 * soon trigger) a track_core_dealloc and put it
				 * on the idle list.  Our signal for this is
				 * get_alloc_proc() being 0. We need to spin and
				 * let whoever is trying to free the core grab
				 * the ksched lock.  We could use an
				 * 'ignore_next_idle' flag per sched_pcore, but
				 * it's not critical anymore.
				 *
				 * Note, we're relying on us being the only
				 * preemptor - if the core was unmapped by
				 * *another* preemptor, there would be no way of
				 * knowing the core was made idle *yet* (the
				 * success branch in another thread).  likewise,
				 * if there were another allocator, the pcore
				 * could have been put on the idle list and then
				 * quickly removed/allocated. */
				cmb();
				while (get_alloc_proc(pcoreid)) {
					/* this loop should be very rare */
					spin_unlock(&sched_lock);
					udelay(1);
					spin_lock(&sched_lock);
				}
			}
			/* no longer need to keep p_to_pre alive */
			proc_decref(proc_to_preempt);
			/* might not be prov to p anymore (rare race). pcoreid
			 * is idle - we might get it later, or maybe we'll give
			 * it to its rightful proc*/
			if (get_prov_proc(pcoreid) != p)
				continue;
		}
		/* At this point, the pcore is idle, regardless of how we got
		 * here (successful preempt, failed preempt, or it was idle in
		 * the first place).  We also know the core is still provisioned
		 * to us.  Lets add it to the corelist for p (so we can give it
		 * to p in bulk later), and track its allocation with p (so our
		 * internal data structures stay in sync). We rely on the fact
		 * that we are the only allocator (pcoreid is still idle,
		 * despite (potentially) unlocking during the preempt attempt
		 * above).  It is guaranteed to be track_dealloc'd() (regardless
		 * of how we got here). */
		corelist[nr_to_grant] = pcoreid;
		nr_to_grant++;
		__track_core_alloc(p, pcoreid);
	}
	/* Now, actually give them out */
	if (nr_to_grant) {
		/* Need to unlock before calling out to proc code.  We are
		 * somewhat relying on being the only one allocating 'thread'
		 * here, since another allocator could have seen these cores (if
		 * they are prov to some proc) and could be trying to give them
		 * out (and assuming they are already on the idle list). */
		spin_unlock(&sched_lock);
		/* give them the cores.  this will start up the extras if
		 * RUNNING_M. */
		spin_lock(&p->proc_lock);
		/* if they fail, it is because they are WAITING or DYING.  we
		 * could give the cores to another proc or whatever.  for the
		 * current type of ksched, we'll just put them back on the pile
		 * and return.  Note, the ksched could check the states after
		 * locking, but it isn't necessary: just need to check at some
		 * point in the ksched loop. */
		if (__proc_give_cores(p, corelist, nr_to_grant)) {
			spin_unlock(&p->proc_lock);
			/* we failed, put the cores and track their dealloc.
			 * lock is protecting those structures. */
			spin_lock(&sched_lock);
			__track_core_dealloc_bulk(p, corelist, nr_to_grant);
		} else {
			/* at some point after giving cores, call proc_run_m()
			 * (harmless on RUNNING_Ms).  You can give small groups
			 * of cores, then run them (which is more efficient than
			 * interleaving runs with the gives for bulk preempted
			 * processes). */
			__proc_run_m(p);
			spin_unlock(&p->proc_lock);
			/* main mcp_ksched wants this held (it came to
			 * __core_req held) */
			spin_lock(&sched_lock);
		}
	}
	/* note the ksched lock is still held */
}

/* Provision a core to a process. This function wraps the primary logic
 * implemented in __provision_core, with a lock, error checking, etc. */
int provision_core(struct proc *p, uint32_t pcoreid)
{
	/* Make sure we aren't asking for something that doesn't exist (bounds
	 * check on the pcore array) */
	if (!(pcoreid < num_cores)) {
		set_errno(ENXIO);
		return -1;
	}
	/* Don't allow the provisioning of LL cores */
	if (is_ll_core(pcoreid)) {
		set_errno(EBUSY);
		return -1;
	}
	/* Note the sched lock protects the tailqs for all procs in this code.
	 * If we need a finer grained sched lock, this is one place where we
	 * could have a different lock */
	spin_lock(&sched_lock);
	__provision_core(p, pcoreid);
	spin_unlock(&sched_lock);
	return 0;
}

/************** Debugging **************/
void sched_diag(void)
{
	struct proc *p;

	spin_lock(&sched_lock);
	TAILQ_FOREACH(p, &runnable_scps, ksched_data.proc_link)
		printk("Runnable _S PID: %d\n", p->pid);
	TAILQ_FOREACH(p, &unrunnable_scps, ksched_data.proc_link)
		printk("Unrunnable _S PID: %d\n", p->pid);
	TAILQ_FOREACH(p, primary_mcps, ksched_data.proc_link)
		printk("Primary MCP PID: %d\n", p->pid);
	TAILQ_FOREACH(p, secondary_mcps, ksched_data.proc_link)
		printk("Secondary MCP PID: %d\n", p->pid);
	spin_unlock(&sched_lock);
	return;
}

void print_resources(struct proc *p)
{
	printk("--------------------\n");
	printk("PID: %d\n", p->pid);
	printk("--------------------\n");
	for (int i = 0; i < MAX_NUM_RESOURCES; i++)
		printk("Res type: %02d, amt wanted: %08d, amt granted: %08d\n",
		       i, p->procdata->res_req[i].amt_wanted,
		       p->procinfo->res_grant[i]);
}

void print_all_resources(void)
{
	/* Hash helper */
	void __print_resources(void *item, void *opaque)
	{
		print_resources((struct proc*)item);
	}
	spin_lock(&pid_hash_lock);
	hash_for_each(pid_hash, __print_resources, NULL);
	spin_unlock(&pid_hash_lock);
}

void next_core_to_alloc(uint32_t pcoreid)
{
	spin_lock(&sched_lock);
	__next_core_to_alloc(pcoreid);
	spin_unlock(&sched_lock);
}

void sort_idle_cores(void)
{
	spin_lock(&sched_lock);
	__sort_idle_cores();
	spin_unlock(&sched_lock);
}