tracing: Use SOFTIRQ_OFFSET for softirq dectection for more accurate results

BugLink: http://bugs.launchpad.net/bugs/1705707
commit c59f29cb144a6a0dfac16ede9dc8eafc02dc56ca upstream.

The 's' flag is supposed to indicate that a softirq is running. This
can be detected by testing the preempt_count with SOFTIRQ_OFFSET.

The current code tests the preempt_count with SOFTIRQ_MASK, which
would be true even when softirqs are disabled but not serving a
softirq.

Link: http://lkml.kernel.org/r/1481300417-3564-1-git-send-email-pkondeti@codeaurora.org
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index f2c9befd516b2d9aa81b2ddccceae607d8de1cbf..dde6126e78df41103518e7b8a3f6ddc654b9b17b 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1660,7 +1660,7 @@ tracing_generic_entry_update(struct trace_entry *entry, unsigned long flags,
                TRACE_FLAG_IRQS_NOSUPPORT |
 #endif
                ((pc & HARDIRQ_MASK) ? TRACE_FLAG_HARDIRQ : 0) |
-               ((pc & SOFTIRQ_MASK) ? TRACE_FLAG_SOFTIRQ : 0) |
+               ((pc & SOFTIRQ_OFFSET) ? TRACE_FLAG_SOFTIRQ : 0) |
                (tif_need_resched() ? TRACE_FLAG_NEED_RESCHED : 0) |
                (test_preempt_need_resched() ? TRACE_FLAG_PREEMPT_RESCHED : 0);
 }