4 files changed, 33 insertions, 11 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index b90a827a4641..88111b08b2c1 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -78,6 +78,13 @@ static int dummy_set_flag(u32 old_flags, u32 bit, int set)
 }
 
 /*
+ * To prevent the comm cache from being overwritten when no
+ * tracing is active, only save the comm when a trace event
+ * occurred.
+ */
+static DEFINE_PER_CPU(bool, trace_cmdline_save);
+
+/*
  * Kill all tracing for good (never come back).
  * It is initialized to 1 but will turn to zero if the initialization
  * of the tracer is successful. But that is the only place that sets
@@ -1135,6 +1142,11 @@ void tracing_record_cmdline(struct task_struct *tsk)
             !tracing_is_on())
                 return;
 
+        if (!__this_cpu_read(trace_cmdline_save))
+                return;
+
+        __this_cpu_write(trace_cmdline_save, false);
+
         trace_save_cmdline(tsk);
 }
 
@@ -1178,13 +1190,20 @@ trace_buffer_lock_reserve(struct ring_buffer *buffer,
         return event;
 }
 
+void
+__buffer_unlock_commit(struct ring_buffer *buffer, struct ring_buffer_event *event)
+{
+        __this_cpu_write(trace_cmdline_save, true);
+        ring_buffer_unlock_commit(buffer, event);
+}
+
 static inline void
 __trace_buffer_unlock_commit(struct ring_buffer *buffer,
                              struct ring_buffer_event *event,
                              unsigned long flags, int pc,
                              int wake)
 {
-        ring_buffer_unlock_commit(buffer, event);
+        __buffer_unlock_commit(buffer, event);
 
         ftrace_trace_stack(buffer, flags, 6, pc);
         ftrace_trace_userstack(buffer, flags, pc);
@@ -1232,7 +1251,7 @@ void trace_nowake_buffer_unlock_commit_regs(struct ring_buffer *buffer,
                                             unsigned long flags, int pc,
                                             struct pt_regs *regs)
 {
-        ring_buffer_unlock_commit(buffer, event);
+        __buffer_unlock_commit(buffer, event);
 
         ftrace_trace_stack_regs(buffer, flags, 0, pc, regs);
         ftrace_trace_userstack(buffer, flags, pc);
@@ -1269,7 +1288,7 @@ trace_function(struct trace_array *tr,
         entry->parent_ip                = parent_ip;
 
         if (!filter_check_discard(call, entry, buffer, event))
-                ring_buffer_unlock_commit(buffer, event);
+                __buffer_unlock_commit(buffer, event);
 }
 
 void
@@ -1362,7 +1381,7 @@ static void __ftrace_trace_stack(struct ring_buffer *buffer,
         entry->size = trace.nr_entries;
 
         if (!filter_check_discard(call, entry, buffer, event))
-                ring_buffer_unlock_commit(buffer, event);
+                __buffer_unlock_commit(buffer, event);
 
  out:
         /* Again, don't let gcc optimize things here */
@@ -1458,7 +1477,7 @@ ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc)
 
         save_stack_trace_user(&trace);
         if (!filter_check_discard(call, entry, buffer, event))
-                ring_buffer_unlock_commit(buffer, event);
+                __buffer_unlock_commit(buffer, event);
 
  out_drop_count:
         __this_cpu_dec(user_stack_count);
@@ -1653,7 +1672,7 @@ int trace_vbprintk(unsigned long ip, const char *fmt, va_list args)
 
         memcpy(entry->buf, tbuffer, sizeof(u32) * len);
         if (!filter_check_discard(call, entry, buffer, event)) {
-                ring_buffer_unlock_commit(buffer, event);
+                __buffer_unlock_commit(buffer, event);
                 ftrace_trace_stack(buffer, flags, 6, pc);
         }
 
@@ -1724,7 +1743,7 @@ int trace_array_vprintk(struct trace_array *tr,
         memcpy(&entry->buf, tbuffer, len);
         entry->buf[len] = '\0';
         if (!filter_check_discard(call, entry, buffer, event)) {
-                ring_buffer_unlock_commit(buffer, event);
+                __buffer_unlock_commit(buffer, event);
                 ftrace_trace_stack(buffer, flags, 6, pc);
         }
  out:
@@ -3993,7 +4012,7 @@ tracing_mark_write(struct file *filp, const char __user *ubuf,
         } else
                 entry->buf[cnt] = '\0';
 
-        ring_buffer_unlock_commit(buffer, event);
+        __buffer_unlock_commit(buffer, event);
 
         written = cnt;
 
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 7824a55bd3fc..839ae003a053 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -359,6 +359,9 @@ struct trace_entry *tracing_get_trace_entry(struct trace_array *tr,
 struct trace_entry *trace_find_next_entry(struct trace_iterator *iter,
                                           int *ent_cpu, u64 *ent_ts);
 
+void __buffer_unlock_commit(struct ring_buffer *buffer,
+                            struct ring_buffer_event *event);
+
 int trace_empty(struct trace_iterator *iter);
 
 void *trace_find_next_entry_inc(struct trace_iterator *iter);
diff --git a/kernel/trace/trace_branch.c b/kernel/trace/trace_branch.c
index bd3e0eef4eaa..95e96842ed29 100644
--- a/kernel/trace/trace_branch.c
+++ b/kernel/trace/trace_branch.c
@@ -77,7 +77,7 @@ probe_likely_condition(struct ftrace_branch_data *f, int val, int expect)
         entry->correct = val == expect;
 
         if (!filter_check_discard(call, entry, buffer, event))
-                ring_buffer_unlock_commit(buffer, event);
+                __buffer_unlock_commit(buffer, event);
 
  out:
         atomic_dec(&tr->data[cpu]->disabled);
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index a84b55879bc4..4edb4b74eb7e 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -223,7 +223,7 @@ int __trace_graph_entry(struct trace_array *tr,
         entry   = ring_buffer_event_data(event);
         entry->graph_ent                        = *trace;
         if (!filter_current_check_discard(buffer, call, entry, event))
-                ring_buffer_unlock_commit(buffer, event);
+                __buffer_unlock_commit(buffer, event);
 
         return 1;
 }
@@ -327,7 +327,7 @@ void __trace_graph_return(struct trace_array *tr,
         entry   = ring_buffer_event_data(event);
         entry->ret                              = *trace;
         if (!filter_current_check_discard(buffer, call, entry, event))
-                ring_buffer_unlock_commit(buffer, event);
+                __buffer_unlock_commit(buffer, event);
 }
 
 void trace_graph_return(struct ftrace_graph_ret *trace)