2 files changed, 24 insertions, 2 deletions

diff --git a/drivers/oprofile/buffer_sync.c b/drivers/oprofile/buffer_sync.c
index d969bb13a25..f9031d31eeb 100644
--- a/drivers/oprofile/buffer_sync.c
+++ b/drivers/oprofile/buffer_sync.c
@@ -524,6 +524,7 @@ void sync_buffer(int cpu)
 {
         struct mm_struct *mm = NULL;
         struct mm_struct *oldmm;
+        unsigned long val;
         struct task_struct *new;
         unsigned long cookie = 0;
         int in_kernel = 1;
@@ -559,10 +560,11 @@ void sync_buffer(int cpu)
                                         state = sb_sample_start;
                                 add_kernel_ctx_switch(flags & IS_KERNEL);
                         }
-                        if (flags & USER_CTX_SWITCH) {
+                        if (flags & USER_CTX_SWITCH
+                            && op_cpu_buffer_get_data(&entry, &val)) {
                                 /* userspace context switch */
+                                new = (struct task_struct *)val;
                                 oldmm = mm;
-                                new = (struct task_struct *)sample->data[0];
                                 release_mm(oldmm);
                                 mm = take_tasks_mm(new);
                                 if (mm != oldmm)
diff --git a/drivers/oprofile/cpu_buffer.h b/drivers/oprofile/cpu_buffer.h
index e178dd2799c..f3437604657 100644
--- a/drivers/oprofile/cpu_buffer.h
+++ b/drivers/oprofile/cpu_buffer.h
@@ -90,6 +90,26 @@ int op_cpu_buffer_add_data(struct op_entry *entry, unsigned long val)
         return entry->size;
 }
 
+/* returns the size of data in the entry */
+static inline
+int op_cpu_buffer_get_size(struct op_entry *entry)
+{
+        return entry->size;
+}
+
+/* returns 0 if empty or the size of data including the current value */
+static inline
+int op_cpu_buffer_get_data(struct op_entry *entry, unsigned long *val)
+{
+        int size = entry->size;
+        if (!size)
+                return 0;
+        *val = *entry->data;
+        entry->size--;
+        entry->data++;
+        return size;
+}
+
 /* extra data flags */
 #define KERNEL_CTX_SWITCH       (1UL << 0)
 #define IS_KERNEL               (1UL << 1)