patches/0044-ring-buffer-Fix-duplicate-results-in-mapping-context.patch

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Date: Thu, 18 Jan 2018 15:42:09 -0500
Subject: [PATCH 44/48] ring-buffer: Fix duplicate results in mapping context
 to bits in recursive lock

In bringing back the context checks, the code checks first if its normal
(non-interrupt) context, and then for NMI then IRQ then softirq. The final
check is redundant. Since the if branch is only hit if the context is one of
NMI, IRQ, or SOFTIRQ, if it's not NMI or IRQ there's no reason to check if
it is SOFTIRQ. The current code returns the same result even if its not a
SOFTIRQ. Which is confusing.

  pc & SOFTIRQ_OFFSET ? 2 : RB_CTX_SOFTIRQ

Is redundant as RB_CTX_SOFTIRQ *is* 2!

Fixes: a0e3a18f4baf ("ring-buffer: Bring back context level recursive checks")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
(cherry picked from commit 0164e0d7e803af3ee1c63770978c728f8778ad01)
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 kernel/trace/ring_buffer.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -2630,8 +2630,7 @@ trace_recursive_lock(struct ring_buffer_
 		bit = RB_CTX_NORMAL;
 	else
 		bit = pc & NMI_MASK ? RB_CTX_NMI :
-			pc & HARDIRQ_MASK ? RB_CTX_IRQ :
-			pc & SOFTIRQ_OFFSET ? 2 : RB_CTX_SOFTIRQ;
+			pc & HARDIRQ_MASK ? RB_CTX_IRQ : RB_CTX_SOFTIRQ;
 
 	if (unlikely(val & (1 << bit)))
 		return 1;