releases/3.18.62/tracing-use-softirq_offset-for-softirq-dectection-for-more-accurate-results.patch

   1 From c59f29cb144a6a0dfac16ede9dc8eafc02dc56ca Mon Sep 17 00:00:00 2001
   2 From: Pavankumar Kondeti <pkondeti@codeaurora.org>
   3 Date: Fri, 9 Dec 2016 21:50:17 +0530
   4 Subject: tracing: Use SOFTIRQ_OFFSET for softirq dectection for more accurate results
   5
   6 From: Pavankumar Kondeti <pkondeti@codeaurora.org>
   7
   8 commit c59f29cb144a6a0dfac16ede9dc8eafc02dc56ca upstream.
   9
  10 The 's' flag is supposed to indicate that a softirq is running. This
  11 can be detected by testing the preempt_count with SOFTIRQ_OFFSET.
  12
  13 The current code tests the preempt_count with SOFTIRQ_MASK, which
  14 would be true even when softirqs are disabled but not serving a
  15 softirq.
  16
  17 Link: http://lkml.kernel.org/r/1481300417-3564-1-git-send-email-pkondeti@codeaurora.org
  18
  19 Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
  20 Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
  21 Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
  22 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  23
  24 ---
  25  kernel/trace/trace.c |    2 +-
  26  1 file changed, 1 insertion(+), 1 deletion(-)
  27
  28 --- a/kernel/trace/trace.c
  29 +++ b/kernel/trace/trace.c
  30 @@ -1587,7 +1587,7 @@ tracing_generic_entry_update(struct trac
  31                 TRACE_FLAG_IRQS_NOSUPPORT |
  32  #endif
  33                 ((pc & HARDIRQ_MASK) ? TRACE_FLAG_HARDIRQ : 0) |
  34 -               ((pc & SOFTIRQ_MASK) ? TRACE_FLAG_SOFTIRQ : 0) |
  35 +               ((pc & SOFTIRQ_OFFSET) ? TRACE_FLAG_SOFTIRQ : 0) |
  36                 (tif_need_resched() ? TRACE_FLAG_NEED_RESCHED : 0) |
  37                 (test_preempt_need_resched() ? TRACE_FLAG_PREEMPT_RESCHED : 0);
  38  }