---

yaml
---
r: 205271
b: refs/heads/master
c: 45a7337
h: refs/heads/master
i:
  205269: 8024a77
  205267: f8d3f83
  205263: 82c1e01
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: c882e0feb937af4e5b991cbd1c81536f37053e86
+refs/heads/master: 45a73372efe4a63f44aa2e1125d4a777c2fdc8d8

trunk/include/linux/perf_event.h

@@ -533,8 +533,10 @@ struct hw_perf_event {
 			struct hrtimer	hrtimer;
 		};
 #ifdef CONFIG_HAVE_HW_BREAKPOINT
-		/* breakpoint */
-		struct arch_hw_breakpoint	info;
+		struct { /* breakpoint */
+			struct arch_hw_breakpoint	info;
+			struct list_head		bp_list;
+		};
 #endif
 	};
 	local64_t			prev_count;

trunk/kernel/hw_breakpoint.c

@@ -41,6 +41,7 @@
 #include <linux/sched.h>
 #include <linux/init.h>
 #include <linux/slab.h>
+#include <linux/list.h>
 #include <linux/cpu.h>
 #include <linux/smp.h>
 
@@ -62,6 +63,9 @@ static DEFINE_PER_CPU(unsigned int, nr_bp_flexible[TYPE_MAX]);
 
 static int nr_slots[TYPE_MAX];
 
+/* Keep track of the breakpoints attached to tasks */
+static LIST_HEAD(bp_task_head);
+
 static int constraints_initialized;
 
 /* Gather the number of total pinned and un-pinned bp in a cpuset */
@@ -103,33 +107,21 @@ static unsigned int max_task_bp_pinned(int cpu, enum bp_type_idx type)
 	return 0;
 }
 
-static int task_bp_pinned(struct task_struct *tsk, enum bp_type_idx type)
+/*
+ * Count the number of breakpoints of the same type and same task.
+ * The given event must be not on the list.
+ */
+static int task_bp_pinned(struct perf_event *bp, enum bp_type_idx type)
 {
-	struct perf_event_context *ctx = tsk->perf_event_ctxp;
-	struct list_head *list;
-	struct perf_event *bp;
-	unsigned long flags;
+	struct perf_event_context *ctx = bp->ctx;
+	struct perf_event *iter;
 	int count = 0;
 
-	if (WARN_ONCE(!ctx, "No perf context for this task"))
-		return 0;
-
-	list = &ctx->event_list;
-
-	raw_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)
-			if (find_slot_idx(bp) == type)
-				count += hw_breakpoint_weight(bp);
+	list_for_each_entry(iter, &bp_task_head, hw.bp_list) {
+		if (iter->ctx == ctx && find_slot_idx(iter) == type)
+			count += hw_breakpoint_weight(iter);
 	}
 
-	raw_spin_unlock_irqrestore(&ctx->lock, flags);
-
 	return count;
 }
 
@@ -149,7 +141,7 @@ fetch_bp_busy_slots(struct bp_busy_slots *slots, struct perf_event *bp,
 		if (!tsk)
 			slots->pinned += max_task_bp_pinned(cpu, type);
 		else
-			slots->pinned += task_bp_pinned(tsk, type);
+			slots->pinned += task_bp_pinned(bp, type);
 		slots->flexible = per_cpu(nr_bp_flexible[type], cpu);
 
 		return;
@@ -162,7 +154,7 @@ fetch_bp_busy_slots(struct bp_busy_slots *slots, struct perf_event *bp,
 		if (!tsk)
 			nr += max_task_bp_pinned(cpu, type);
 		else
-			nr += task_bp_pinned(tsk, type);
+			nr += task_bp_pinned(bp, type);
 
 		if (nr > slots->pinned)
 			slots->pinned = nr;
@@ -188,18 +180,19 @@ fetch_this_slot(struct bp_busy_slots *slots, int weight)
 /*
  * 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,
+static void toggle_bp_task_slot(struct perf_event *bp, int cpu, bool enable,
 				enum bp_type_idx type, int weight)
 {
 	unsigned int *tsk_pinned;
 	int old_count = 0;
 	int old_idx = 0;
 	int idx = 0;
 
-	old_count = task_bp_pinned(tsk, type);
+	old_count = task_bp_pinned(bp, type);
 	old_idx = old_count - 1;
 	idx = old_idx + weight;
 
+	/* tsk_pinned[n] is the number of tasks having n breakpoints */
 	tsk_pinned = per_cpu(nr_task_bp_pinned[type], cpu);
 	if (enable) {
 		tsk_pinned[idx]++;
@@ -222,23 +215,30 @@ toggle_bp_slot(struct perf_event *bp, bool enable, enum bp_type_idx type,
 	int cpu = bp->cpu;
 	struct task_struct *tsk = bp->ctx->task;
 
+	/* Pinned counter cpu profiling */
+	if (!tsk) {
+
+		if (enable)
+			per_cpu(nr_cpu_bp_pinned[type], bp->cpu) += weight;
+		else
+			per_cpu(nr_cpu_bp_pinned[type], bp->cpu) -= weight;
+		return;
+	}
+
 	/* Pinned counter task profiling */
-	if (tsk) {
-		if (cpu >= 0) {
-			toggle_bp_task_slot(tsk, cpu, enable, type, weight);
-			return;
-		}
 
+	if (!enable)
+		list_del(&bp->hw.bp_list);
+
+	if (cpu >= 0) {
+		toggle_bp_task_slot(bp, cpu, enable, type, weight);
+	} else {
 		for_each_online_cpu(cpu)
-			toggle_bp_task_slot(tsk, cpu, enable, type, weight);
-		return;
+			toggle_bp_task_slot(bp, cpu, enable, type, weight);
 	}
 
-	/* Pinned counter cpu profiling */
 	if (enable)
-		per_cpu(nr_cpu_bp_pinned[type], bp->cpu) += weight;
-	else
-		per_cpu(nr_cpu_bp_pinned[type], bp->cpu) -= weight;
+		list_add_tail(&bp->hw.bp_list, &bp_task_head);
 }
 
 /*
@@ -301,6 +301,10 @@ static int __reserve_bp_slot(struct perf_event *bp)
 	weight = hw_breakpoint_weight(bp);
 
 	fetch_bp_busy_slots(&slots, bp, type);
+	/*
+	 * Simulate the addition of this breakpoint to the constraints
+	 * and see the result.
+	 */
 	fetch_this_slot(&slots, weight);
 
 	/* Flexible counters need to keep at least one slot */