[PATCH] Regression: partial revert "tracing: Remove lock_depth from event entry"

[Arjan van de Ven]

This patch partially reverts commit e6e1e2593592a8f6f6380496655d8c6f67431266.
That commit changed the structure layout of the trace structure, which in
turn broke PowerTOP (1.9x generation) quite badly.

I appreciate not wanting to expose the variable in question, and PowerTOP was
not using it, so I've replaced the variable with just a padding byte....
... that way if in the future a new field is needed it can just use this padding
byte.

Signed-off-by: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
---
 include/linux/ftrace_event.h |    1 +
 kernel/trace/trace.c         |    1 +
 kernel/trace/trace_events.c  |    1 +
 3 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 22b32af1..b5a550a 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -37,6 +37,7 @@ struct trace_entry {
 	unsigned char		flags;
 	unsigned char		preempt_count;
 	int			pid;
+	int			padding;
 };
 
 #define FTRACE_MAX_EVENT						\
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index d38c16a..1cb49be 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1110,6 +1110,7 @@ tracing_generic_entry_update(struct trace_entry *entry, unsigned long flags,
 
 	entry->preempt_count		= pc & 0xff;
 	entry->pid			= (tsk) ? tsk->pid : 0;
+	entry->padding			= 0;
 	entry->flags =
 #ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT
 		(irqs_disabled_flags(flags) ? TRACE_FLAG_IRQS_OFF : 0) |
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index e88f74f..2fe1103 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -116,6 +116,7 @@ static int trace_define_common_fields(void)
 	__common_field(unsigned char, flags);
 	__common_field(unsigned char, preempt_count);
 	__common_field(int, pid);
+	__common_field(int, padding);
 
 	return ret;
 }
-- 
1.7.2.2


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