linux-kernel - Fix powerTOP regression with 2.6.39-rc5

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Date:	Fri, 06 May 2011 13:08:23 -0700
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Ingo Molnar <mingo@...e.hu>, Steven Rostedt <rostedt@...dmis.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Fix powerTOP regression with 2.6.39-rc5

 From c2db3ab8cff0d1cfb9582fc149df2794978a332e Mon Sep 17 00:00:00 2001
From: Arjan van de Ven <arjan@...ux.intel.com>
Date: Thu, 5 May 2011 23:55:18 -0400
Subject: [PATCH] Regression: partial revert "tracing: Remove lock_depth 
from event entry"

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 field....
... that way if in the future a new field is needed it can just use this 
padding
variable.

Signed-off-by: Arjan van de Ven <arjan@...ux.intel.com>
---
  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


View attachment "0001-Regression-partial-revert-tracing-Remove-lock_depth.patch" of type "text/plain" (2127 bytes)