1 files changed, 53 insertions, 37 deletions

diff --git a/kernel/hw_breakpoint.c b/kernel/hw_breakpoint.c
index 7a56b22e0602..d71a987fd2bf 100644
--- a/kernel/hw_breakpoint.c
+++ b/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;
@@ -188,7 +180,7 @@ 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;
@@ -196,10 +188,11 @@ static void toggle_bp_task_slot(struct task_struct *tsk, int cpu, bool enable,
         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 +215,41 @@ 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);
+}
+
+/*
+ * Function to perform processor-specific cleanup during unregistration
+ */
+__weak void arch_unregister_hw_breakpoint(struct perf_event *bp)
+{
+        /*
+         * A weak stub function here for those archs that don't define
+         * it inside arch/.../kernel/hw_breakpoint.c
+         */
 }
 
 /*
@@ -301,6 +312,10 @@ 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 */
@@ -339,6 +354,7 @@ void release_bp_slot(struct perf_event *bp)
 {
         mutex_lock(&nr_bp_mutex);
 
+        arch_unregister_hw_breakpoint(bp);
         __release_bp_slot(bp);
 
         mutex_unlock(&nr_bp_mutex);