1 files changed, 53 insertions, 13 deletions

diff --git a/kernel/hw_breakpoint.c b/kernel/hw_breakpoint.c
index dbcbf6a33a08..8a5c7d55ac9f 100644
--- a/kernel/hw_breakpoint.c
+++ b/kernel/hw_breakpoint.c
@@ -40,6 +40,7 @@
 #include <linux/percpu.h>
 #include <linux/sched.h>
 #include <linux/init.h>
+#include <linux/cpu.h>
 #include <linux/smp.h>
 
 #include <linux/hw_breakpoint.h>
@@ -242,38 +243,70 @@ static void toggle_bp_slot(struct perf_event *bp, bool enable)
  *       ((per_cpu(nr_bp_flexible, *) > 1) + max(per_cpu(nr_cpu_bp_pinned, *))
  *            + max(per_cpu(nr_task_bp_pinned, *))) < HBP_NUM
  */
-int reserve_bp_slot(struct perf_event *bp)
+static 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);
 
         /* Flexible counters need to keep at least one slot */
-        if (slots.pinned + (!!slots.flexible) == HBP_NUM) {
-                ret = -ENOSPC;
-                goto end;
-        }
+        if (slots.pinned + (!!slots.flexible) == HBP_NUM)
+                return -ENOSPC;
 
         toggle_bp_slot(bp, true);
 
-end:
+        return 0;
+}
+
+int reserve_bp_slot(struct perf_event *bp)
+{
+        int ret;
+
+        mutex_lock(&nr_bp_mutex);
+
+        ret = __reserve_bp_slot(bp);
+
         mutex_unlock(&nr_bp_mutex);
 
         return ret;
 }
 
+static void __release_bp_slot(struct perf_event *bp)
+{
+        toggle_bp_slot(bp, false);
+}
+
 void release_bp_slot(struct perf_event *bp)
 {
         mutex_lock(&nr_bp_mutex);
 
-        toggle_bp_slot(bp, false);
+        __release_bp_slot(bp);
 
         mutex_unlock(&nr_bp_mutex);
 }
 
+/*
+ * Allow the kernel debugger to reserve breakpoint slots without
+ * taking a lock using the dbg_* variant of for the reserve and
+ * release breakpoint slots.
+ */
+int dbg_reserve_bp_slot(struct perf_event *bp)
+{
+        if (mutex_is_locked(&nr_bp_mutex))
+                return -1;
+
+        return __reserve_bp_slot(bp);
+}
+
+int dbg_release_bp_slot(struct perf_event *bp)
+{
+        if (mutex_is_locked(&nr_bp_mutex))
+                return -1;
+
+        __release_bp_slot(bp);
+
+        return 0;
+}
 
 int register_perf_hw_breakpoint(struct perf_event *bp)
 {
@@ -295,6 +328,10 @@ int register_perf_hw_breakpoint(struct perf_event *bp)
         if (!bp->attr.disabled || !bp->overflow_handler)
                 ret = arch_validate_hwbkpt_settings(bp, bp->ctx->task);
 
+        /* if arch_validate_hwbkpt_settings() fails then release bp slot */
+        if (ret)
+                release_bp_slot(bp);
+
         return ret;
 }
 
@@ -388,7 +425,8 @@ register_wide_hw_breakpoint(struct perf_event_attr *attr,
         if (!cpu_events)
                 return ERR_PTR(-ENOMEM);
 
-        for_each_possible_cpu(cpu) {
+        get_online_cpus();
+        for_each_online_cpu(cpu) {
                 pevent = per_cpu_ptr(cpu_events, cpu);
                 bp = perf_event_create_kernel_counter(attr, cpu, -1, triggered);
 
@@ -399,18 +437,20 @@ register_wide_hw_breakpoint(struct perf_event_attr *attr,
                         goto fail;
                 }
         }
+        put_online_cpus();
 
         return cpu_events;
 
 fail:
-        for_each_possible_cpu(cpu) {
+        for_each_online_cpu(cpu) {
                 pevent = per_cpu_ptr(cpu_events, cpu);
                 if (IS_ERR(*pevent))
                         break;
                 unregister_hw_breakpoint(*pevent);
         }
+        put_online_cpus();
+
         free_percpu(cpu_events);
-        /* return the error if any */
         return ERR_PTR(err);
 }
 EXPORT_SYMBOL_GPL(register_wide_hw_breakpoint);