* Copyright (C) 2007 Alan Stern
* Copyright (C) IBM Corporation, 2009
* Copyright (C) 2009, Frederic Weisbecker <fweisbec@gmail.com>
+ *
+ * Thanks to Ingo Molnar for his many suggestions.
*/
/*
#include <asm/debugreg.h>
#endif
-static atomic_t bp_slot;
+/*
+ * Constraints data
+ */
+
+/* Number of pinned cpu breakpoints in a cpu */
+static DEFINE_PER_CPU(unsigned int, nr_cpu_bp_pinned);
-int reserve_bp_slot(struct perf_event *bp)
+/* Number of pinned task breakpoints in a cpu */
+static DEFINE_PER_CPU(unsigned int, task_bp_pinned[HBP_NUM]);
+
+/* Number of non-pinned cpu/task breakpoints in a cpu */
+static DEFINE_PER_CPU(unsigned int, nr_bp_flexible);
+
+/* Gather the number of total pinned and un-pinned bp in a cpuset */
+struct bp_busy_slots {
+ unsigned int pinned;
+ unsigned int flexible;
+};
+
+/* Serialize accesses to the above constraints */
+static DEFINE_MUTEX(nr_bp_mutex);
+
+/*
+ * Report the maximum number of pinned breakpoints a task
+ * have in this cpu
+ */
+static unsigned int max_task_bp_pinned(int cpu)
{
- if (atomic_inc_return(&bp_slot) == HBP_NUM) {
- atomic_dec(&bp_slot);
+ int i;
+ unsigned int *tsk_pinned = per_cpu(task_bp_pinned, cpu);
- return -ENOSPC;
+ for (i = HBP_NUM -1; i >= 0; i--) {
+ if (tsk_pinned[i] > 0)
+ return i + 1;
}
return 0;
}
+/*
+ * Report the number of pinned/un-pinned breakpoints we have in
+ * a given cpu (cpu > -1) or in all of them (cpu = -1).
+ */
+static void fetch_bp_busy_slots(struct bp_busy_slots *slots, int cpu)
+{
+ if (cpu >= 0) {
+ slots->pinned = per_cpu(nr_cpu_bp_pinned, cpu);
+ slots->pinned += max_task_bp_pinned(cpu);
+ slots->flexible = per_cpu(nr_bp_flexible, cpu);
+
+ return;
+ }
+
+ for_each_online_cpu(cpu) {
+ unsigned int nr;
+
+ nr = per_cpu(nr_cpu_bp_pinned, cpu);
+ nr += max_task_bp_pinned(cpu);
+
+ if (nr > slots->pinned)
+ slots->pinned = nr;
+
+ nr = per_cpu(nr_bp_flexible, cpu);
+
+ if (nr > slots->flexible)
+ slots->flexible = nr;
+ }
+}
+
+/*
+ * Add a pinned breakpoint for the given task in our constraint table
+ */
+static void toggle_bp_task_slot(struct task_struct *tsk, int cpu, bool enable)
+{
+ int count = 0;
+ struct perf_event *bp;
+ struct perf_event_context *ctx = tsk->perf_event_ctxp;
+ unsigned int *task_bp_pinned;
+ struct list_head *list;
+ unsigned long flags;
+
+ if (WARN_ONCE(!ctx, "No perf context for this task"))
+ return;
+
+ list = &ctx->event_list;
+
+ spin_lock_irqsave(&ctx->lock, flags);
+
+ /*
+ * The current breakpoint counter is not included in the list
+ * at the open() callback time
+ */
+ list_for_each_entry(bp, list, event_entry) {
+ if (bp->attr.type == PERF_TYPE_BREAKPOINT)
+ count++;
+ }
+
+ spin_unlock_irqrestore(&ctx->lock, flags);
+
+ if (WARN_ONCE(count < 0, "No breakpoint counter found in the counter list"))
+ return;
+
+ task_bp_pinned = per_cpu(task_bp_pinned, cpu);
+ if (enable) {
+ task_bp_pinned[count]++;
+ if (count > 0)
+ task_bp_pinned[count-1]--;
+ } else {
+ task_bp_pinned[count]--;
+ if (count > 0)
+ task_bp_pinned[count-1]++;
+ }
+}
+
+/*
+ * Add/remove the given breakpoint in our constraint table
+ */
+static void toggle_bp_slot(struct perf_event *bp, bool enable)
+{
+ int cpu = bp->cpu;
+ struct task_struct *tsk = bp->ctx->task;
+
+ /* Pinned counter task profiling */
+ if (tsk) {
+ if (cpu >= 0) {
+ toggle_bp_task_slot(tsk, cpu, enable);
+ return;
+ }
+
+ for_each_online_cpu(cpu)
+ toggle_bp_task_slot(tsk, cpu, enable);
+ return;
+ }
+
+ /* Pinned counter cpu profiling */
+ if (enable)
+ per_cpu(nr_cpu_bp_pinned, bp->cpu)++;
+ else
+ per_cpu(nr_cpu_bp_pinned, bp->cpu)--;
+}
+
+/*
+ * Contraints to check before allowing this new breakpoint counter:
+ *
+ * == Non-pinned counter == (Considered as pinned for now)
+ *
+ * - If attached to a single cpu, check:
+ *
+ * (per_cpu(nr_bp_flexible, cpu) || (per_cpu(nr_cpu_bp_pinned, cpu)
+ * + max(per_cpu(task_bp_pinned, cpu)))) < HBP_NUM
+ *
+ * -> If there are already non-pinned counters in this cpu, it means
+ * there is already a free slot for them.
+ * Otherwise, we check that the maximum number of per task
+ * breakpoints (for this cpu) plus the number of per cpu breakpoint
+ * (for this cpu) doesn't cover every registers.
+ *
+ * - If attached to every cpus, check:
+ *
+ * (per_cpu(nr_bp_flexible, *) || (max(per_cpu(nr_cpu_bp_pinned, *))
+ * + max(per_cpu(task_bp_pinned, *)))) < HBP_NUM
+ *
+ * -> This is roughly the same, except we check the number of per cpu
+ * bp for every cpu and we keep the max one. Same for the per tasks
+ * breakpoints.
+ *
+ *
+ * == Pinned counter ==
+ *
+ * - If attached to a single cpu, check:
+ *
+ * ((per_cpu(nr_bp_flexible, cpu) > 1) + per_cpu(nr_cpu_bp_pinned, cpu)
+ * + max(per_cpu(task_bp_pinned, cpu))) < HBP_NUM
+ *
+ * -> Same checks as before. But now the nr_bp_flexible, if any, must keep
+ * one register at least (or they will never be fed).
+ *
+ * - If attached to every cpus, check:
+ *
+ * ((per_cpu(nr_bp_flexible, *) > 1) + max(per_cpu(nr_cpu_bp_pinned, *))
+ * + max(per_cpu(task_bp_pinned, *))) < HBP_NUM
+ */
+int reserve_bp_slot(struct perf_event *bp)
+{
+ struct bp_busy_slots slots = {0};
+ int ret = 0;
+
+ mutex_lock(&nr_bp_mutex);
+
+ fetch_bp_busy_slots(&slots, bp->cpu);
+
+ /* Flexible counters need to keep at least one slot */
+ if (slots.pinned + (!!slots.flexible) == HBP_NUM) {
+ ret = -ENOSPC;
+ goto end;
+ }
+
+ toggle_bp_slot(bp, true);
+
+end:
+ mutex_unlock(&nr_bp_mutex);
+
+ return ret;
+}
+
void release_bp_slot(struct perf_event *bp)
{
- atomic_dec(&bp_slot);
+ mutex_lock(&nr_bp_mutex);
+
+ toggle_bp_slot(bp, false);
+
+ mutex_unlock(&nr_bp_mutex);
}
+
int __register_perf_hw_breakpoint(struct perf_event *bp)
{
int ret;
projects / openwrt / staging / blogic.git / commitdiff