/*
   *  kernel/sched_cpupri.c
   *
   *  CPU priority management
   *
   *  Copyright (C) 2007-2008 Novell
   *
   *  Author: Gregory Haskins <ghaskins@novell.com>
   *
   *  This code tracks the priority of each CPU so that global migration
   *  decisions are easy to calculate.  Each CPU can be in a state as follows:
   *
   *                 (INVALID), IDLE, NORMAL, RT1, ... RT99
   *
   *  going from the lowest priority to the highest.  CPUs in the INVALID state
   *  are not eligible for routing.  The system maintains this state with
   *  a 2 dimensional bitmap (the first for priority class, the second for cpus
   *  in that class).  Therefore a typical application without affinity
   *  restrictions can find a suitable CPU with O(1) complexity (e.g. two bit
   *  searches).  For tasks with affinity restrictions, the algorithm has a
   *  worst case complexity of O(min(102, nr_domcpus)), though the scenario that
   *  yields the worst case search is fairly contrived.
   *
   *  This program is free software; you can redistribute it and/or
   *  modify it under the terms of the GNU General Public License
   *  as published by the Free Software Foundation; version 2
   *  of the License.
   */

  #include <linux/gfp.h>

  #include "sched_cpupri.h"
  
  /* Convert between a 140 based task->prio, and our 102 based cpupri */
  static int convert_prio(int prio)
  {
  	int cpupri;
  
  	if (prio == CPUPRI_INVALID)
  		cpupri = CPUPRI_INVALID;
  	else if (prio == MAX_PRIO)
  		cpupri = CPUPRI_IDLE;
  	else if (prio >= MAX_RT_PRIO)
  		cpupri = CPUPRI_NORMAL;
  	else
  		cpupri = MAX_RT_PRIO - prio + 1;
  
  	return cpupri;
  }
  
  #define for_each_cpupri_active(array, idx)                    \

  	for_each_set_bit(idx, array, CPUPRI_NR_PRIORITIES)

  
  /**
   * cpupri_find - find the best (lowest-pri) CPU in the system
   * @cp: The cpupri context
   * @p: The task

   * @lowest_mask: A mask to fill in with selected CPUs (or NULL)

   *
   * Note: This function returns the recommended CPUs as calculated during the

   * current invocation.  By the time the call returns, the CPUs may have in

   * fact changed priorities any number of times.  While not ideal, it is not
   * an issue of correctness since the normal rebalancer logic will correct
   * any discrepancies created by racing against the uncertainty of the current
   * priority configuration.
   *
   * Returns: (int)bool - CPUs were found
   */
  int cpupri_find(struct cpupri *cp, struct task_struct *p,

  		struct cpumask *lowest_mask)

  {
  	int                  idx      = 0;
  	int                  task_pri = convert_prio(p->prio);
  
  	for_each_cpupri_active(cp->pri_active, idx) {
  		struct cpupri_vec *vec  = &cp->pri_to_cpu[idx];

  
  		if (idx >= task_pri)
  			break;

  		if (cpumask_any_and(&p->cpus_allowed, vec->mask) >= nr_cpu_ids)

  			continue;

  		if (lowest_mask) {

  			cpumask_and(lowest_mask, &p->cpus_allowed, vec->mask);

  
  			/*
  			 * We have to ensure that we have at least one bit
  			 * still set in the array, since the map could have
  			 * been concurrently emptied between the first and
  			 * second reads of vec->mask.  If we hit this
  			 * condition, simply act as though we never hit this
  			 * priority level and continue on.
  			 */
  			if (cpumask_any(lowest_mask) >= nr_cpu_ids)
  				continue;
  		}

  		return 1;
  	}
  
  	return 0;
  }
  
  /**
   * cpupri_set - update the cpu priority setting
   * @cp: The cpupri context
   * @cpu: The target cpu
   * @pri: The priority (INVALID-RT99) to assign to this CPU
   *
   * Note: Assumes cpu_rq(cpu)->lock is locked
   *
   * Returns: (void)
   */
  void cpupri_set(struct cpupri *cp, int cpu, int newpri)
  {
  	int                 *currpri = &cp->cpu_to_pri[cpu];
  	int                  oldpri  = *currpri;
  	unsigned long        flags;
  
  	newpri = convert_prio(newpri);
  
  	BUG_ON(newpri >= CPUPRI_NR_PRIORITIES);
  
  	if (newpri == oldpri)
  		return;
  
  	/*
  	 * If the cpu was currently mapped to a different value, we

  	 * need to map it to the new value then remove the old value.
  	 * Note, we must add the new value first, otherwise we risk the
  	 * cpu being cleared from pri_active, and this cpu could be
  	 * missed for a push or pull.

  	 */

  	if (likely(newpri != CPUPRI_INVALID)) {
  		struct cpupri_vec *vec = &cp->pri_to_cpu[newpri];

  		raw_spin_lock_irqsave(&vec->lock, flags);

  		cpumask_set_cpu(cpu, vec->mask);

  		vec->count++;
  		if (vec->count == 1)
  			set_bit(newpri, cp->pri_active);

  		raw_spin_unlock_irqrestore(&vec->lock, flags);

  	}

  	if (likely(oldpri != CPUPRI_INVALID)) {
  		struct cpupri_vec *vec  = &cp->pri_to_cpu[oldpri];

  		raw_spin_lock_irqsave(&vec->lock, flags);

  
  		vec->count--;
  		if (!vec->count)
  			clear_bit(oldpri, cp->pri_active);
  		cpumask_clear_cpu(cpu, vec->mask);

  		raw_spin_unlock_irqrestore(&vec->lock, flags);

  	}

  
  	*currpri = newpri;
  }
  
  /**
   * cpupri_init - initialize the cpupri structure
   * @cp: The cpupri context

   * @bootmem: true if allocations need to use bootmem

   *

   * Returns: -ENOMEM if memory fails.

   */

  int cpupri_init(struct cpupri *cp, bool bootmem)

  {

  	gfp_t gfp = GFP_KERNEL;

  	int i;

  	if (bootmem)
  		gfp = GFP_NOWAIT;

  	memset(cp, 0, sizeof(*cp));
  
  	for (i = 0; i < CPUPRI_NR_PRIORITIES; i++) {
  		struct cpupri_vec *vec = &cp->pri_to_cpu[i];

  		raw_spin_lock_init(&vec->lock);

  		vec->count = 0;

  		if (!zalloc_cpumask_var(&vec->mask, gfp))

  			goto cleanup;

  	}
  
  	for_each_possible_cpu(i)
  		cp->cpu_to_pri[i] = CPUPRI_INVALID;

  	return 0;
  
  cleanup:
  	for (i--; i >= 0; i--)
  		free_cpumask_var(cp->pri_to_cpu[i].mask);
  	return -ENOMEM;

  }

  /**
   * cpupri_cleanup - clean up the cpupri structure
   * @cp: The cpupri context
   */
  void cpupri_cleanup(struct cpupri *cp)
  {
  	int i;

  	for (i = 0; i < CPUPRI_NR_PRIORITIES; i++)
  		free_cpumask_var(cp->pri_to_cpu[i].mask);
  }