/* Number of pinned CPU breakpoints globally. */
static struct bp_slots_histogram cpu_pinned[TYPE_MAX];
+/* Number of pinned CPU-independent task breakpoints. */
+static struct bp_slots_histogram tsk_pinned_all[TYPE_MAX];
/* Keep track of the breakpoints attached to tasks */
static struct rhltable task_bps_ht;
for (i = 0; i < TYPE_MAX; i++) {
if (!bp_slots_histogram_alloc(&cpu_pinned[i], i))
goto err;
+ if (!bp_slots_histogram_alloc(&tsk_pinned_all[i], i))
+ goto err;
}
return 0;
if (err_cpu == cpu)
break;
}
- for (i = 0; i < TYPE_MAX; i++)
+ for (i = 0; i < TYPE_MAX; i++) {
bp_slots_histogram_free(&cpu_pinned[i]);
+ bp_slots_histogram_free(&tsk_pinned_all[i]);
+ }
return -ENOMEM;
}
return 0;
}
+static int
+bp_slots_histogram_max_merge(struct bp_slots_histogram *hist1, struct bp_slots_histogram *hist2,
+ enum bp_type_idx type)
+{
+ for (int i = hw_breakpoint_slots_cached(type) - 1; i >= 0; i--) {
+ const int count1 = atomic_read(&hist1->count[i]);
+ const int count2 = atomic_read(&hist2->count[i]);
+
+ /* Catch unexpected writers; we want a stable snapshot. */
+ ASSERT_EXCLUSIVE_WRITER(hist1->count[i]);
+ ASSERT_EXCLUSIVE_WRITER(hist2->count[i]);
+ if (count1 + count2 > 0)
+ return i + 1;
+ WARN(count1 < 0, "inconsistent breakpoint slots histogram");
+ WARN(count2 < 0, "inconsistent breakpoint slots histogram");
+ }
+
+ return 0;
+}
+
#ifndef hw_breakpoint_weight
static inline int hw_breakpoint_weight(struct perf_event *bp)
{
* toggle_bp_task_slot() to tsk_pinned, and we get a stable snapshot.
*/
lockdep_assert_held_write(&bp_cpuinfo_sem);
- return bp_slots_histogram_max(tsk_pinned, type);
+ return bp_slots_histogram_max_merge(tsk_pinned, &tsk_pinned_all[type], type);
}
/*
}
/*
- * Add a pinned breakpoint for the given task in our constraint table
- */
-static void toggle_bp_task_slot(struct perf_event *bp, int cpu,
- enum bp_type_idx type, int weight)
-{
- struct bp_slots_histogram *tsk_pinned = &get_bp_info(cpu, type)->tsk_pinned;
-
- /*
- * If bp->hw.target, tsk_pinned is only modified, but not used
- * otherwise. We can permit concurrent updates as long as there are no
- * other uses: having acquired bp_cpuinfo_sem as a reader allows
- * concurrent updates here. Uses of tsk_pinned will require acquiring
- * bp_cpuinfo_sem as a writer to stabilize tsk_pinned's value.
- */
- lockdep_assert_held_read(&bp_cpuinfo_sem);
- bp_slots_histogram_add(tsk_pinned, task_bp_pinned(cpu, bp, type), weight);
-}
-
-/*
* Add/remove the given breakpoint in our constraint table
*/
static int
-toggle_bp_slot(struct perf_event *bp, bool enable, enum bp_type_idx type,
- int weight)
+toggle_bp_slot(struct perf_event *bp, bool enable, enum bp_type_idx type, int weight)
{
- const struct cpumask *cpumask = cpumask_of_bp(bp);
- int cpu;
+ int cpu, next_tsk_pinned;
if (!enable)
weight = -weight;
- /* Pinned counter cpu profiling */
if (!bp->hw.target) {
+ /*
+ * Update the pinned CPU slots, in per-CPU bp_cpuinfo and in the
+ * global histogram.
+ */
struct bp_cpuinfo *info = get_bp_info(bp->cpu, type);
lockdep_assert_held_write(&bp_cpuinfo_sem);
return 0;
}
- /* Pinned counter task profiling */
- for_each_cpu(cpu, cpumask)
- toggle_bp_task_slot(bp, cpu, type, weight);
+ /*
+ * If bp->hw.target, tsk_pinned is only modified, but not used
+ * otherwise. We can permit concurrent updates as long as there are no
+ * other uses: having acquired bp_cpuinfo_sem as a reader allows
+ * concurrent updates here. Uses of tsk_pinned will require acquiring
+ * bp_cpuinfo_sem as a writer to stabilize tsk_pinned's value.
+ */
+ lockdep_assert_held_read(&bp_cpuinfo_sem);
+
+ /*
+ * Update the pinned task slots, in per-CPU bp_cpuinfo and in the global
+ * histogram. We need to take care of 4 cases:
+ *
+ * 1. This breakpoint targets all CPUs (cpu < 0), and there may only
+ * exist other task breakpoints targeting all CPUs. In this case we
+ * can simply update the global slots histogram.
+ *
+ * 2. This breakpoint targets a specific CPU (cpu >= 0), but there may
+ * only exist other task breakpoints targeting all CPUs.
+ *
+ * a. On enable: remove the existing breakpoints from the global
+ * slots histogram and use the per-CPU histogram.
+ *
+ * b. On disable: re-insert the existing breakpoints into the global
+ * slots histogram and remove from per-CPU histogram.
+ *
+ * 3. Some other existing task breakpoints target specific CPUs. Only
+ * update the per-CPU slots histogram.
+ */
+
+ if (!enable) {
+ /*
+ * Remove before updating histograms so we can determine if this
+ * was the last task breakpoint for a specific CPU.
+ */
+ int ret = rhltable_remove(&task_bps_ht, &bp->hw.bp_list, task_bps_ht_params);
+
+ if (ret)
+ return ret;
+ }
+ /*
+ * Note: If !enable, next_tsk_pinned will not count the to-be-removed breakpoint.
+ */
+ next_tsk_pinned = task_bp_pinned(-1, bp, type);
+
+ if (next_tsk_pinned >= 0) {
+ if (bp->cpu < 0) { /* Case 1: fast path */
+ if (!enable)
+ next_tsk_pinned += hw_breakpoint_weight(bp);
+ bp_slots_histogram_add(&tsk_pinned_all[type], next_tsk_pinned, weight);
+ } else if (enable) { /* Case 2.a: slow path */
+ /* Add existing to per-CPU histograms. */
+ for_each_possible_cpu(cpu) {
+ bp_slots_histogram_add(&get_bp_info(cpu, type)->tsk_pinned,
+ 0, next_tsk_pinned);
+ }
+ /* Add this first CPU-pinned task breakpoint. */
+ bp_slots_histogram_add(&get_bp_info(bp->cpu, type)->tsk_pinned,
+ next_tsk_pinned, weight);
+ /* Rebalance global task pinned histogram. */
+ bp_slots_histogram_add(&tsk_pinned_all[type], next_tsk_pinned,
+ -next_tsk_pinned);
+ } else { /* Case 2.b: slow path */
+ /* Remove this last CPU-pinned task breakpoint. */
+ bp_slots_histogram_add(&get_bp_info(bp->cpu, type)->tsk_pinned,
+ next_tsk_pinned + hw_breakpoint_weight(bp), weight);
+ /* Remove all from per-CPU histograms. */
+ for_each_possible_cpu(cpu) {
+ bp_slots_histogram_add(&get_bp_info(cpu, type)->tsk_pinned,
+ next_tsk_pinned, -next_tsk_pinned);
+ }
+ /* Rebalance global task pinned histogram. */
+ bp_slots_histogram_add(&tsk_pinned_all[type], 0, next_tsk_pinned);
+ }
+ } else { /* Case 3: slow path */
+ const struct cpumask *cpumask = cpumask_of_bp(bp);
+
+ for_each_cpu(cpu, cpumask) {
+ next_tsk_pinned = task_bp_pinned(cpu, bp, type);
+ if (!enable)
+ next_tsk_pinned += hw_breakpoint_weight(bp);
+ bp_slots_histogram_add(&get_bp_info(cpu, type)->tsk_pinned,
+ next_tsk_pinned, weight);
+ }
+ }
/*
* Readers want a stable snapshot of the per-task breakpoint list.
if (enable)
return rhltable_insert(&task_bps_ht, &bp->hw.bp_list, task_bps_ht_params);
- else
- return rhltable_remove(&task_bps_ht, &bp->hw.bp_list, task_bps_ht_params);
+
+ return 0;
}
__weak int arch_reserve_bp_slot(struct perf_event *bp)
*/
if (WARN_ON(atomic_read(&cpu_pinned[type].count[slot])))
return true;
+
+ if (atomic_read(&tsk_pinned_all[type].count[slot]))
+ return true;
}
}
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