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@@ -0,0 +1,174 @@
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+/*
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+ * kernel/sched_cpupri.c
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+ *
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+ * CPU priority management
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+ *
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+ * Copyright (C) 2007-2008 Novell
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+ *
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+ * Author: Gregory Haskins <ghaskins@novell.com>
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+ *
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+ * This code tracks the priority of each CPU so that global migration
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+ * decisions are easy to calculate. Each CPU can be in a state as follows:
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+ *
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+ * (INVALID), IDLE, NORMAL, RT1, ... RT99
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+ *
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+ * going from the lowest priority to the highest. CPUs in the INVALID state
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+ * are not eligible for routing. The system maintains this state with
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+ * a 2 dimensional bitmap (the first for priority class, the second for cpus
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+ * in that class). Therefore a typical application without affinity
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+ * restrictions can find a suitable CPU with O(1) complexity (e.g. two bit
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+ * searches). For tasks with affinity restrictions, the algorithm has a
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+ * worst case complexity of O(min(102, nr_domcpus)), though the scenario that
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+ * yields the worst case search is fairly contrived.
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+ *
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+ * This program is free software; you can redistribute it and/or
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+ * modify it under the terms of the GNU General Public License
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+ * as published by the Free Software Foundation; version 2
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+ * of the License.
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+ */
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+
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+#include "sched_cpupri.h"
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+
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+/* Convert between a 140 based task->prio, and our 102 based cpupri */
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+static int convert_prio(int prio)
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+{
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+ int cpupri;
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+
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+ if (prio == CPUPRI_INVALID)
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+ cpupri = CPUPRI_INVALID;
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+ else if (prio == MAX_PRIO)
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+ cpupri = CPUPRI_IDLE;
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+ else if (prio >= MAX_RT_PRIO)
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+ cpupri = CPUPRI_NORMAL;
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+ else
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+ cpupri = MAX_RT_PRIO - prio + 1;
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+
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+ return cpupri;
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+}
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+
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+#define for_each_cpupri_active(array, idx) \
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+ for (idx = find_first_bit(array, CPUPRI_NR_PRIORITIES); \
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+ idx < CPUPRI_NR_PRIORITIES; \
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+ idx = find_next_bit(array, CPUPRI_NR_PRIORITIES, idx+1))
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+
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+/**
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+ * cpupri_find - find the best (lowest-pri) CPU in the system
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+ * @cp: The cpupri context
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+ * @p: The task
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+ * @lowest_mask: A mask to fill in with selected CPUs
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+ *
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+ * Note: This function returns the recommended CPUs as calculated during the
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+ * current invokation. By the time the call returns, the CPUs may have in
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+ * fact changed priorities any number of times. While not ideal, it is not
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+ * an issue of correctness since the normal rebalancer logic will correct
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+ * any discrepancies created by racing against the uncertainty of the current
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+ * priority configuration.
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+ *
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+ * Returns: (int)bool - CPUs were found
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+ */
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+int cpupri_find(struct cpupri *cp, struct task_struct *p,
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+ cpumask_t *lowest_mask)
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+{
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+ int idx = 0;
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+ int task_pri = convert_prio(p->prio);
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+
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+ for_each_cpupri_active(cp->pri_active, idx) {
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+ struct cpupri_vec *vec = &cp->pri_to_cpu[idx];
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+ cpumask_t mask;
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+
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+ if (idx >= task_pri)
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+ break;
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+
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+ cpus_and(mask, p->cpus_allowed, vec->mask);
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+
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+ if (cpus_empty(mask))
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+ continue;
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+
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+ *lowest_mask = mask;
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+ return 1;
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+ }
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+
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+ return 0;
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+}
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+
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+/**
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+ * cpupri_set - update the cpu priority setting
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+ * @cp: The cpupri context
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+ * @cpu: The target cpu
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+ * @pri: The priority (INVALID-RT99) to assign to this CPU
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+ *
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+ * Note: Assumes cpu_rq(cpu)->lock is locked
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+ *
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+ * Returns: (void)
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+ */
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+void cpupri_set(struct cpupri *cp, int cpu, int newpri)
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+{
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+ int *currpri = &cp->cpu_to_pri[cpu];
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+ int oldpri = *currpri;
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+ unsigned long flags;
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+
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+ newpri = convert_prio(newpri);
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+
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+ BUG_ON(newpri >= CPUPRI_NR_PRIORITIES);
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+
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+ if (newpri == oldpri)
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+ return;
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+
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+ /*
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+ * If the cpu was currently mapped to a different value, we
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+ * first need to unmap the old value
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+ */
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+ if (likely(oldpri != CPUPRI_INVALID)) {
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+ struct cpupri_vec *vec = &cp->pri_to_cpu[oldpri];
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+
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+ spin_lock_irqsave(&vec->lock, flags);
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+
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+ vec->count--;
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+ if (!vec->count)
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+ clear_bit(oldpri, cp->pri_active);
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+ cpu_clear(cpu, vec->mask);
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+
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+ spin_unlock_irqrestore(&vec->lock, flags);
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+ }
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+
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+ if (likely(newpri != CPUPRI_INVALID)) {
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+ struct cpupri_vec *vec = &cp->pri_to_cpu[newpri];
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+
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+ spin_lock_irqsave(&vec->lock, flags);
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+
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+ cpu_set(cpu, vec->mask);
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+ vec->count++;
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+ if (vec->count == 1)
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+ set_bit(newpri, cp->pri_active);
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+
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+ spin_unlock_irqrestore(&vec->lock, flags);
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+ }
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+
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+ *currpri = newpri;
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+}
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+
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+/**
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+ * cpupri_init - initialize the cpupri structure
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+ * @cp: The cpupri context
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+ *
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+ * Returns: (void)
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+ */
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+void cpupri_init(struct cpupri *cp)
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+{
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+ int i;
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+
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+ memset(cp, 0, sizeof(*cp));
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+
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+ for (i = 0; i < CPUPRI_NR_PRIORITIES; i++) {
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+ struct cpupri_vec *vec = &cp->pri_to_cpu[i];
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+
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+ spin_lock_init(&vec->lock);
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+ vec->count = 0;
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+ cpus_clear(vec->mask);
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+ }
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+
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+ for_each_possible_cpu(i)
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+ cp->cpu_to_pri[i] = CPUPRI_INVALID;
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+}
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+
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+
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Gregory Haskins