tracing: move tgid out of generic entry and into userstack

The userstack trace required the recording of the tgid entry.
Unfortunately, it was added to the generic entry where it wasted
4 bytes of every entry and was only used by one entry.

This patch moves it out of the generic field and moves it into the
only user (userstack_entry).
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

include/linux/ftrace_event.h

@@ -34,7 +34,6 @@ struct trace_entry {
 	unsigned char		flags;
 	unsigned char		preempt_count;
 	int			pid;
-	int			tgid;
 };
 
 #define FTRACE_MAX_EVENT						\

kernel/trace/trace.c

@@ -886,7 +886,6 @@ tracing_generic_entry_update(struct trace_entry *entry, unsigned long flags,
 
 	entry->preempt_count		= pc & 0xff;
 	entry->pid			= (tsk) ? tsk->pid : 0;
-	entry->tgid			= (tsk) ? tsk->tgid : 0;
 	entry->flags =
 #ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT
 		(irqs_disabled_flags(flags) ? TRACE_FLAG_IRQS_OFF : 0) |
@@ -1068,6 +1067,7 @@ ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc)
 		return;
 	entry	= ring_buffer_event_data(event);
 
+	entry->tgid		= current->tgid;
 	memset(&entry->caller, 0, sizeof(entry->caller));
 
 	trace.nr_entries	= 0;

kernel/trace/trace.h

@@ -101,6 +101,7 @@ struct stack_entry {
 
 struct userstack_entry {
 	struct trace_entry	ent;
+	unsigned int		tgid;
 	unsigned long		caller[FTRACE_STACK_ENTRIES];
 };
 

kernel/trace/trace_events.c

@@ -86,7 +86,6 @@ int trace_define_common_fields(struct ftrace_event_call *call)
 	__common_field(unsigned char, flags);
 	__common_field(unsigned char, preempt_count);
 	__common_field(int, pid);
-	__common_field(int, tgid);
 
 	return ret;
 }
@@ -572,13 +571,11 @@ static int trace_write_header(struct trace_seq *s)
 				"\tfield:%s %s;\toffset:%zu;\tsize:%zu;\n"
 				"\tfield:%s %s;\toffset:%zu;\tsize:%zu;\n"
 				"\tfield:%s %s;\toffset:%zu;\tsize:%zu;\n"
-				"\tfield:%s %s;\toffset:%zu;\tsize:%zu;\n"
 				"\n",
 				FIELD(unsigned short, type),
 				FIELD(unsigned char, flags),
 				FIELD(unsigned char, preempt_count),
-				FIELD(int, pid),
-				FIELD(int, tgid));
+				FIELD(int, pid));
 }
 
 static ssize_t

kernel/trace/trace_output.c

@@ -407,7 +407,7 @@ seq_print_userip_objs(const struct userstack_entry *entry, struct trace_seq *s,
 		 * since individual threads might have already quit!
 		 */
 		rcu_read_lock();
-		task = find_task_by_vpid(entry->ent.tgid);
+		task = find_task_by_vpid(entry->tgid);
 		if (task)
 			mm = get_task_mm(task);
 		rcu_read_unlock();