path: root/litmus/dgl.c

#include <linux/sched.h>
#include <linux/slab.h>

#include <litmus/litmus.h>
#include <litmus/dgl.h>
#include <litmus/sched_trace.h>

#define DEBUG_DGL

#define STRACE2(fmt, args...) printk(KERN_ERR fmt, ## args)

#ifdef DEBUG_DGL
#define TRACE(fmt, args...) STRACE(fmt, ## args)
#define TRACE_GREQ(greq, fmt, args...)					       \
	TRACE("(greq-%s/%llu) " fmt, (greq->task ? greq->task->comm : "greq"), \
	      (greq->task ? greq->task->pid : (unsigned long long)greq), ## args)
#else
#define TRACE(fmt, args...)
#define TRACE_GREQ(greq, fmt, args...)
#endif

#define MASK_SIZE     (sizeof(unsigned long) * 8)

/* Return number of MASK_SIZE fields needed to store a mask in d */
#define WP(num, word) (num / word + (num % word != 0))
#define MASK_WORDS(d) WP(d->num_resources, MASK_SIZE)

/* Word, bit -> resource id */
#define ri(w, b) (w * MASK_SIZE + b)

 /* For loop, where @i iterates over each set bit in @bit_arr */
#define for_each_resource(bit_arr, d, w, b, i)				\
	for(w = 0; w < MASK_WORDS(d); ++w)				\
		 for(b = find_first_bit(&bit_arr[w],MASK_SIZE), i = ri(w, b);  \
		     b < MASK_SIZE;					       \
		     b = find_next_bit(&bit_arr[w],MASK_SIZE,b+1), i = ri(w, b))

/* Return resource id in dgl @d for resource @r */
#define resource_id(d, r) ((((void*)r) - (void*)((d)->resources))/ sizeof(*r))

/* Return request group of req @r for resource @i */
#define req_group(r, i) (container_of(((void*)r) - sizeof(*r)*(i),	\
				      struct dgl_group_req, requests))

static inline void set_bit_value(int bit, unsigned long *word, int value)
{
	if (value) {
		__set_bit(bit, word);
	} else {
		clear_bit(bit, word);
	}
}

/*
 * Resource id -> word, bit
 */
static inline void mask_idx(int resource, int *word, int *bit)
{
	*word = resource / MASK_SIZE;
	*bit  = resource % MASK_SIZE;
}

/*
 * Logical OR of words in @arr.
 */
static int arr_to_bool(struct dgl *dgl, unsigned long *arr)
{
	int word, ret = 0;
	for (word = 0; word < MASK_WORDS(dgl) && !ret; word++) {
		ret |= arr[word];
	}
	return (ret != 0);
}

static void print_queue(struct dgl *dgl, struct list_head *list)
{
	struct dgl_req *pos;
	struct dgl_group_req *greq;

	list_for_each_entry(pos, list, list) {
		greq = pos->greq;
		sched_trace_log_message("(%s-%d:r%d-p%d-b%d)->", greq->task->comm,
					greq->task->pid, pos->replicas,
					arr_to_bool(dgl, greq->need_prio),
					arr_to_bool(dgl, greq->blocked));
	}
	sched_trace_log_message("\n");
}

static void print_resource(struct dgl *dgl, struct dgl_resource *resource)
{
	STRACE2("\tResource %d, real_free: %d, goal_free: %d\n",
		resource_id(dgl, resource),
		resource->real_free,
		resource->goal_free);
	STRACE2("\t  acquired: ");
	print_queue(dgl, &resource->acquired);
	STRACE2("\t  will_acquire:");
	print_queue(dgl, &resource->will_acquire);
	STRACE2("\t  waiting:");
	print_queue(dgl, &resource->waiting);
	STRACE2("\t  will_wait:");
	print_queue(dgl, &resource->will_wait);
}

/*
 * Print stats and queues of every resource to the trace log.
 */
static void print_state(struct dgl *dgl)
{
	int i;
	struct dgl_resource *resource;

	sched_trace_log_message("\n");
	STRACE2("\t\tDGL: requests: %d\n", dgl->requests);

	for (i = 0; i < dgl->num_resources; ++i) {
		resource = &dgl->resources[i];

		if (!resource) {
			STRACE2("\tResource %d is null!\n", i);
		}

		if (!list_empty(&resource->waiting)    ||
		    !list_empty(&resource->will_wait)  ||
		    !list_empty(&resource->acquired)   ||
		    !list_empty(&resource->will_acquire)) {

			print_resource(dgl, resource);
		}
	}
	STRACE2("Dump complete\n");
	sched_trace_log_message("\n");
}

#ifdef DEBUG_DGL
#define BUG_DUMP(dgl, cond)			\
	do {					\
	if (cond) {				\
		STRACE2("BAD: %s", #cond);	\
		print_state(dgl);		\
		BUG();				\
	}} while(0)
#else
#define BUG_DUMP(dgl, cond)
#endif


static int higher_prio(struct dgl_group_req *a, struct dgl_group_req *b)
{
	return (a->priority < b->priority ||
		(a->priority == b->priority && (a->task->pid < b->task->pid)));
}

static void release_cpu(struct dgl *dgl, struct dgl_group_req *greq)
{
	int cpu = greq->cpu;

	BUG_DUMP(dgl, dgl->acquired[cpu] != greq);

	dgl->acquired[cpu] = NULL;
}

static void take_cpu(struct dgl *dgl, struct dgl_group_req *greq)
{
	int cpu = greq->cpu;

	BUG_DUMP(dgl, dgl->acquired[cpu]);

	dgl->acquired[cpu] = greq;
}

/*
 * Count lower priority replicas of @greq for @list in @resource.
 * @start   If specified, begin search at location at *@start
 */
static int __get_lp_replicas(struct dgl *dgl, struct dgl_group_req *greq,
			     struct dgl_resource *resource,
			     struct dgl_req **start,
			     struct list_head *list)
{
	int replicas = 0;
	struct list_head *pos_l;
	struct dgl_req *pos;

	pos_l = (*start) ? &(*start)->list : list;
	pos = list_entry(pos_l, struct dgl_req, list);

	list_for_each_entry(pos, list, list) {
		if (higher_prio(pos->greq, greq)) {
			break;
		}
		replicas += pos->replicas;
		BUG_DUMP(dgl, replicas > dgl->num_replicas);
	}

	if (start) {
		*start = pos;
	}

	return replicas;
}

/*
 * Count lower priority replicas of @greq in the acquired and will_acquire
 * queues of @resource.
 * @start_a  Request to start counting replicas in acquired list
 * @start_wa "" "" for will_acquire
 */
static int get_lp_replicas(struct dgl *dgl, struct dgl_group_req *greq,
			   struct dgl_resource *resource,
			   struct dgl_req **start_a, struct dgl_req **start_wa)
{
	int reps = 0;

	reps += __get_lp_replicas(dgl, greq, resource, start_a, &resource->acquired);
	reps += __get_lp_replicas(dgl, greq, resource, start_wa, &resource->will_acquire);

	return reps;
}

/*
 * Add @req to @list in priority order.
 * @reverse  Reverse priority
 */
static void add_request(struct list_head *list, struct dgl_req *req,
			int reverse)
{
	struct list_head *last;
	struct dgl_req *acquired;
	struct dgl_group_req *greqa, *greqb;

	BUG_ON(in_list(&req->list));

	last = list;
	list_for_each_entry(acquired, list, list) {
		if (!reverse) {
			greqa = req->greq;
			greqb = acquired->greq;
		} else {
			greqa = acquired->greq;
			greqb = req->greq;
		}
		if (higher_prio(greqa, greqb)) {
			break;
		}
		last = &acquired->list;
	}
	list_add(&req->list, last);
}

/*
 * Add @req to a waiting or will_wait list.
 */
static void add_waiting(struct dgl *dgl, struct list_head *list, struct dgl_req *req)
{
	BUG_DUMP(dgl, !arr_to_bool(dgl, req->greq->need_prio));
	add_request(list, req, 0);
}

/*
 * Add @req to an acquired or will_acquire list.
 */
static void add_acquired(struct dgl *dgl, struct list_head *list, struct dgl_req *req)
{
	BUG_DUMP(dgl, arr_to_bool(dgl, req->greq->need_prio));
	add_request(list, req, 1);
}

/*
 * Cancel preemption of @greq's requests.
 */
static void will_wait_to_acquire(struct dgl *dgl, struct dgl_group_req *greq)
{
	int w, b, i;
	struct dgl_req *our_req;
	struct dgl_resource *resource;

	BUG_DUMP(dgl, arr_to_bool(dgl, greq->need_prio));
	BUG_DUMP(dgl, arr_to_bool(dgl, greq->blocked));
	BUG_DUMP(dgl, dgl->acquired[greq->cpu] != greq);

	TRACE_GREQ(greq, "(WILL_WAIT)->(ACQUIRE)\n");

	for_each_resource(greq->requested, dgl, w, b, i) {
		our_req  = &greq->requests[i];
		resource = &dgl->resources[i];

		resource->goal_free -= our_req->replicas;

		list_del_init(&our_req->list);
		add_acquired(dgl, &resource->acquired, our_req);

		BUG_DUMP(dgl, resource->goal_free < 0);
	}
}

/*
 * Preempt @greq's requests.
 */
static void acquired_to_will_wait(struct dgl *dgl, struct dgl_group_req *greq,
				  struct dgl_group_req *blocked)
{
	int w, b, i;
	struct dgl_req *our_req;
	struct dgl_resource *resource;

	BUG_DUMP(dgl, !arr_to_bool(dgl, greq->need_prio));
	BUG_DUMP(dgl, dgl->acquired[greq->cpu] != greq);

	TRACE_GREQ(greq, "(ACQUIRED)->(WILL_WAIT)\n");

	for_each_resource(greq->requested, dgl, w, b, i) {
		our_req  = &greq->requests[i];
		resource = &dgl->resources[i];

		resource->goal_free += our_req->replicas;

		list_del_init(&our_req->list);
		add_waiting(dgl, &resource->will_wait, our_req);

		BUG_DUMP(dgl, resource->goal_free > dgl->num_replicas);
	}
}

/*
 * Cancel @greq's resource acquisition.
 */
static void will_acquire_to_waiting(struct dgl *dgl, struct dgl_group_req *greq)
{
	int w, b, i;
	struct dgl_req *our_req;
	struct dgl_resource *resource;

	BUG_DUMP(dgl, !arr_to_bool(dgl, greq->need_prio));
	BUG_DUMP(dgl, dgl->acquired[greq->cpu] == greq);

	TRACE_GREQ(greq, "(WILL_ACQUIRE)->(WAITING)\n");

	for_each_resource(greq->requested, dgl, w, b, i) {
		our_req  = &greq->requests[i];
		resource = &dgl->resources[i];

		resource->goal_free += our_req->replicas;

		list_del_init(&our_req->list);
		add_waiting(dgl, &resource->waiting, our_req);

		BUG_DUMP(dgl, resource->goal_free < 0);
	}
}

#define next_list(list, reverse) ((reverse) ? (list)->prev : (list)->next)

/*
 * @return        Next request from list_a U list_b
 * @reverse_prio  Return lower-priority requests
 * @revearse_read Read lists from end to beginning
 * @tmp_a and @tmp_b store the next item in the list so that the returned
 * item can be safely deleted during iteration
 */
static struct dgl_req *next_union(struct list_head *list_a,
				  struct list_head *list_b,
				  struct list_head **tmp_a,
				  struct list_head **tmp_b,
				  int reverse_prio, int reverse_read)
{
	int higher;
	struct dgl_req *next_a, *next_b;

	next_a = next_b = NULL;

	*tmp_a = (*tmp_a) ? *tmp_a : next_list(list_a, reverse_read);
	*tmp_b = (*tmp_b) ? *tmp_b : next_list(list_b, reverse_read);

	if (*tmp_a != list_a) {
		next_a = list_entry(*tmp_a, struct dgl_req, list);
	}
	if (*tmp_b != list_b) {
		next_b = list_entry(*tmp_b, struct dgl_req, list);
	}

	if (next_a && next_b) {
		higher = higher_prio(next_a->greq, next_b->greq);
		if ((reverse_prio && higher)|| (!reverse_prio && !higher)) {
			*tmp_b = next_list(&next_b->list, reverse_read);
			return next_b;
		} else {
			*tmp_a = next_list(&next_a->list, reverse_read);
			return next_a;
		}
	} else if (next_a) {
		*tmp_a = next_list(&next_a->list, reverse_read);
		return next_a;
	} else if (next_b) {
		*tmp_b = next_list(&next_b->list, reverse_read);
		return next_b;
	} else {
		return NULL;
	}
}

/*
 * @return Next logically waiting request in @resource
 */
static struct dgl_req *next_waiting(struct dgl_resource *resource,
				    struct list_head **pos_a,
				    struct list_head **pos_b,
				    int reverse)
{
	int reverse_prio = (reverse) ? 1 : 0;
	return next_union(&resource->waiting, &resource->will_wait,
			  pos_a, pos_b, reverse_prio, reverse);
}

/*
 * @return Next logically acquired request in @resource
 */
static struct dgl_req *next_acquired(struct dgl_resource *resource,
				     struct list_head **pos_a,
				     struct list_head **pos_b)
{
	return next_union(&resource->acquired, &resource->will_acquire,
			  pos_a, pos_b, 1, 0);
}


/*
 * Recalculate all need_prio bits for requests in @resource.
 */
static void update_prio(struct dgl *dgl, struct dgl_resource *resource)
{
	int lp_replicas, w, b, i;
	struct dgl_req *req, *acq_a, *acq_b;
	struct dgl_group_req *greq;
	struct list_head *tmp_a, *tmp_b;

	lp_replicas = resource->goal_free;
	tmp_a = tmp_b = NULL;
	acq_a = acq_b = NULL;

	i = resource_id(dgl, resource);
	mask_idx(i, &w, &b);

	while ((req = next_waiting(resource, &tmp_a, &tmp_b, 1))) {
		greq = req->greq;

		lp_replicas += get_lp_replicas(dgl, greq, resource,
					       &acq_a, &acq_b);

		set_bit_value(b, &greq->need_prio[w],
			      lp_replicas < req->replicas);

		BUG_DUMP(dgl, lp_replicas > dgl->num_replicas);
	}
}

/*
 * Recalculate all blocked bits for requests in @resource.
 */
static void update_blocked(struct dgl *dgl, struct dgl_resource *resource)
{
	int w, b, i;
	struct dgl_req *req;
	struct dgl_group_req *greq;

	i = resource_id(dgl, resource);
	mask_idx(i, &w, &b);

	list_for_each_entry(req, &resource->will_acquire, list) {
		greq = req->greq;
		set_bit_value(b, &greq->blocked[w],
			      resource->real_free < req->replicas);
	}
}

/*
 * Move @greq from logically running to physically running.
 */
static void will_acquire_to_acquire(struct dgl *dgl, struct dgl_group_req *greq)
{
	int w, b, i;
	struct dgl_req *our_req;
	struct dgl_resource *resource;

	BUG_DUMP(dgl, arr_to_bool(dgl, greq->need_prio));
	BUG_DUMP(dgl, arr_to_bool(dgl, greq->blocked));
	BUG_DUMP(dgl, dgl->acquired[greq->cpu] != greq);

	TRACE_GREQ(greq, "(WILL_ACQUIRE)->(ACQUIRE)\n");

	for_each_resource(greq->requested, dgl, w, b, i) {
		our_req  = &greq->requests[i];
		resource = &dgl->resources[i];

		list_del_init(&our_req->list);
		add_acquired(dgl, &resource->acquired, our_req);

		resource->real_free -= our_req->replicas;
		BUG_DUMP(dgl, (resource->real_free < 0));
	}
}

/*
 * If any requests in @resource are unblocked, schedule them.
 */
static void pull_blocked(struct dgl *dgl, struct dgl_resource *resource)
{
	struct dgl_req *req, *tmp;
	struct dgl_group_req *greq;

	list_for_each_entry_safe(req, tmp, &resource->will_acquire, list) {
		greq = req->greq;
		if (!arr_to_bool(dgl, greq->blocked)) {
			take_cpu(dgl, greq);
			will_acquire_to_acquire(dgl, greq);
			dgl->cpu_acquired(greq);
			update_blocked(dgl, resource);
		}
	}

}

/*
 * Free up enough goal_free in @resource to run @our_req.
 */
static void bump_resource(struct dgl *dgl, struct dgl_resource *resource,
			  struct dgl_group_req *greq, struct dgl_req *our_req)
{
	int w;
	struct list_head *tmp_a, *tmp_b;
	struct dgl_req *next;
	struct dgl_group_req *next_greq;

	tmp_a = tmp_b = NULL;

	while ((next = next_acquired(resource, &tmp_b, &tmp_a))) {
		if (resource->goal_free >= our_req->replicas) {
			break;
		}

		next_greq = next->greq;

		BUG_DUMP(dgl, higher_prio(next_greq, greq));

		for (w = 0; w < MASK_WORDS(dgl); w++) {
			next_greq->need_prio[w] |=
				next_greq->requested[w] &
				greq->requested[w];
		}

		if (dgl->acquired[next_greq->cpu] == next_greq) {
			BUG_DUMP(dgl, dgl->acquired[next_greq->cpu] != next_greq);
				acquired_to_will_wait(dgl, next_greq, greq);
		} else {
			will_acquire_to_waiting(dgl, next_greq);
		}

		dgl->cpu_preempted(next_greq);
	}
}

/*
 * Prepare high-priority request for acquisition.
 */
static void waiting_to_will_acquire(struct dgl *dgl, struct dgl_group_req *greq)
{
	int w, b, i;
	struct dgl_req *our_req;
	struct dgl_resource *resource;

	BUG_DUMP(dgl, arr_to_bool(dgl, greq->need_prio));
	BUG_DUMP(dgl, dgl->acquired[greq->cpu] == greq);

	TRACE_GREQ(greq, "(WAITING)->(WILL_ACQUIRE)\n");

	for_each_resource(greq->requested, dgl, w, b, i) {
		our_req  = &greq->requests[i];
		resource = &dgl->resources[i];

		list_del_init(&our_req->list);

		bump_resource(dgl, resource, greq, our_req);
		resource->goal_free -= our_req->replicas;

		BUG_DUMP(dgl, resource->goal_free < 0);

		add_acquired(dgl, &resource->will_acquire, our_req);
		update_prio(dgl, resource);
	}
}

/*
 * Logically waiting but physically running request moves to physically waiting.
 */
static void will_wait_to_waiting(struct dgl *dgl, struct dgl_group_req *greq)
{
	int w, b, i;
	struct dgl_req *our_req;
	struct dgl_resource *resource;

	BUG_DUMP(dgl, !arr_to_bool(dgl, greq->need_prio));
	BUG_DUMP(dgl, dgl->acquired[greq->cpu] == greq);

	TRACE_GREQ(greq, "(WILL_WAIT)->(WAITING)\n");

	for_each_resource(greq->requested, dgl, w, b, i) {
		our_req  = &greq->requests[i];
		resource = &dgl->resources[i];

		list_del_init(&our_req->list);
		add_waiting(dgl, &resource->waiting, our_req);

		resource->real_free += our_req->replicas;
		update_blocked(dgl, resource);

		BUG_DUMP(dgl, resource->real_free > dgl->num_replicas);
	}

	for_each_resource(greq->requested, dgl, w, b, i) {
		pull_blocked(dgl, &dgl->resources[i]);
	}
}

/*
 * If any requests in @resource have priority to logically acquire, start
 * resource acquisitions.
 */
static void pull_prio(struct dgl *dgl, struct dgl_resource *resource)
{
	struct dgl_req *next;
	struct dgl_group_req *greq;
	struct list_head *tmp_a, *tmp_b;

	tmp_a = tmp_b = NULL;

	while ((next = next_waiting(resource, &tmp_a, &tmp_b, 0))) {
		greq = next->greq;

		if (!arr_to_bool(dgl, greq->need_prio)) {
			if (dgl->acquired[greq->cpu] == greq) {
				will_wait_to_acquire(dgl, greq);
			} else {
				waiting_to_will_acquire(dgl, greq);
			}
			update_prio(dgl, resource);
		}
	}
}

/**
 * add_group_req - put in @greq for resources on @cpu.
 */
void add_group_req(struct dgl *dgl, struct dgl_group_req *greq, int cpu)
{
	int w, b, i, lp_reps;
	struct dgl_req *our_req;
	struct dgl_resource *resource;

	greq->cpu = cpu;
	greq->priority = dgl->assign_priority(dgl, greq);

	++dgl->requests;

	TRACE_GREQ(greq, "Group request added for CPU %d\n", cpu);
	BUG_DUMP(dgl, dgl->acquired[cpu] == greq);

	for (w = 0; w < MASK_WORDS(dgl); w++) {
		greq->need_prio[w] = greq->requested[w];
		greq->blocked[w]   = greq->requested[w];
	}

	for_each_resource(greq->requested, dgl, w, b, i) {
		our_req  = &greq->requests[i];
		resource = &dgl->resources[i];

		add_waiting(dgl, &resource->waiting, our_req);

		lp_reps = get_lp_replicas(dgl, greq, resource, NULL, NULL) +
			resource->goal_free;

		set_bit_value(b, &greq->need_prio[w],
			      lp_reps < our_req->replicas);
	}

	/* Take resources if it has priority */
	if (!arr_to_bool(dgl, greq->need_prio)) {
		for_each_resource(greq->requested, dgl, w, b, i) {
			our_req  = &greq->requests[i];
			resource = &dgl->resources[i];

			pull_prio(dgl, resource);
			set_bit_value(b, &greq->blocked[w],
				      resource->real_free < our_req->replicas);
		}

		/* Take CPUs if its not blocked */
		if (!arr_to_bool(dgl, greq->blocked)) {
			for_each_resource(greq->requested, dgl, w, b, i) {
				pull_blocked(dgl, &dgl->resources[i]);
			}
		}
	}
}

/**
 * update_group_req - update state of @greq in @dgl.
 */
void update_group_req(struct dgl *dgl, struct dgl_group_req *greq)
{
	if (arr_to_bool(dgl, greq->need_prio) &&
	    !arr_to_bool(dgl, greq->blocked)  &&
	    dgl->acquired[greq->cpu] == greq) {
		TRACE_GREQ(greq, "Blocker has called update\n");
		release_cpu(dgl, greq);
		will_wait_to_waiting(dgl, greq);
	} else {
		TRACE_GREQ(greq, "Unused update\n");
	}

	BUG_DUMP(dgl, arr_to_bool(dgl, greq->blocked) &&
		 dgl->acquired[greq->cpu] == greq);
}

/**
 * remove_group_req - remove @greq from contention in @dgl.
 */
void remove_group_req(struct dgl *dgl, struct dgl_group_req *greq)
{
	int w, b, i, running, has_prio;
	struct dgl_req *our_req;
	struct dgl_resource *resource;

	TRACE_GREQ(greq, "Removing group request\n");

	running  = dgl->acquired[greq->cpu] == greq;
	has_prio = !arr_to_bool(dgl, greq->need_prio);

	if (dgl->acquired[greq->cpu] == greq) {
		release_cpu(dgl, greq);
	}

	for_each_resource(greq->requested, dgl, w, b, i) {
		our_req  = &greq->requests[i];
		resource = &dgl->resources[i];

		if (running) {
			resource->real_free += our_req->replicas;
			BUG_DUMP(dgl, resource->real_free > dgl->num_replicas);
			update_blocked(dgl, resource);
		}
		if (has_prio) {
			resource->goal_free += our_req->replicas;
			BUG_DUMP(dgl, resource->goal_free > dgl->num_replicas);
			update_prio(dgl, resource);
		}

		list_del_init(&our_req->list);
	}

	/* if (!arr_to_bool(dgl, greq->need_prio)) { */
	/* 	for_each_resource(greq->requested, dgl, w, b, i) { */
	/* 		update_prio(dgl, &dgl->resources[i]); */
	/* 	} */
	/* 	for_each_resource(greq->requested, dgl, w, b, i) { */
	/* 		pull_prio(dgl, &dgl->resources[i]); */
	/* 	} */
	/* } */

	/* for_each_resource(greq->requested, dgl, w, b, i) { */
	/* 	resource = &dgl->resources[i]; */
	/* 	if (running)  update_blocked(dgl, resource); */
	/* 	if (has_prio) update_prio(dgl, resource); */
	/* } */
	for_each_resource(greq->requested, dgl, w, b, i) {
		resource = &dgl->resources[i];
		if (running)  pull_blocked(dgl, resource);
		if (has_prio) pull_prio(dgl, resource);
	}

	--dgl->requests;
}

/**
 * set_req - create request for @replicas of @resource.
 */
void set_req(struct dgl *dgl, struct dgl_group_req *greq,
	     int resource, int replicas)
{
	int word, bit;
	struct dgl_req *req;

	if (replicas > dgl->num_replicas)
		replicas = dgl->num_replicas;

	mask_idx(resource, &word, &bit);
	__set_bit(bit, &greq->requested[word]);

	TRACE_GREQ(greq, "requesting %d of %d\n", replicas, resource);

	req = &greq->requests[resource];

	req->greq = greq;
	req->replicas = replicas;

	INIT_LIST_HEAD(&req->list);
	BUG_DUMP(dgl, in_list(&req->list));
}

static void dummy_acquired(struct dgl_group_req *greq){}

static unsigned long long timestamp_prio (struct dgl *dgl, struct dgl_group_req *greq)
{
	return dgl->ts++;
}

void dgl_init(struct dgl *dgl, unsigned long num_resources,
	      unsigned long num_replicas)
{
	int i;
	struct dgl_resource *resource;

	dgl->num_replicas  = num_replicas;
	dgl->num_resources = num_resources;

	dgl->resources = kmalloc(sizeof(*dgl->resources) * num_resources,
				 GFP_ATOMIC);
	dgl->acquired  = kmalloc(sizeof(*dgl->acquired) * num_online_cpus(),
				 GFP_ATOMIC);

	for (i = 0; i < num_online_cpus(); ++i)
		dgl->acquired[i] = NULL;

	for (i = 0; i < num_resources; i++) {
		resource = &dgl->resources[i];

		INIT_LIST_HEAD(&resource->waiting);
		INIT_LIST_HEAD(&resource->acquired);
		INIT_LIST_HEAD(&resource->will_wait);
		INIT_LIST_HEAD(&resource->will_acquire);
		resource->real_free = dgl->num_replicas;
		resource->goal_free = dgl->num_replicas;
	}

	dgl->requests = 0;
	dgl->ts = 0;
	dgl->cpu_acquired = dummy_acquired;
	dgl->cpu_preempted = NULL;
	dgl->assign_priority = timestamp_prio;
}

void dgl_free(struct dgl *dgl)
{
	kfree(dgl->resources);
	kfree(dgl->acquired);
}

void dgl_group_req_init(struct dgl *dgl, struct dgl_group_req *greq)
{
	int i;

	greq->requested = kmalloc(sizeof(*greq->requested) * MASK_WORDS(dgl),
				  GFP_ATOMIC);
	greq->need_prio = kmalloc(sizeof(*greq->need_prio) * MASK_WORDS(dgl),
				  GFP_ATOMIC);
	greq->blocked   = kmalloc(sizeof(*greq->need_prio) * MASK_WORDS(dgl),
				  GFP_ATOMIC);
	greq->requests  = kmalloc(sizeof(*greq->requests) * dgl->num_resources,
				  GFP_ATOMIC);

	BUG_DUMP(dgl, !greq->requested);
	BUG_DUMP(dgl, !greq->need_prio);
	BUG_DUMP(dgl, !greq->requests);

	greq->cpu = NO_CPU;
	for (i = 0; i < MASK_WORDS(dgl); ++i) {
		greq->requested[i] = 0;
		greq->need_prio[i] = 0;
	}
}

void dgl_group_req_free(struct dgl_group_req *greq)
{
	kfree(greq->requested);
	kfree(greq->need_prio);
	kfree(greq->requests);
}