linux-kernel - [PATCH] tracing: Remove outdated comment in stack handling

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Message-ID: <20200727092840.18659-1-vincent.whitchurch@axis.com>
Date:   Mon, 27 Jul 2020 11:28:40 +0200
From:   Vincent Whitchurch <vincent.whitchurch@...s.com>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>
CC:     <kernel@...s.com>, <tglx@...utronix.de>,
        Vincent Whitchurch <vincent.whitchurch@...s.com>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH] tracing: Remove outdated comment in stack handling

This comment describes the behaviour before commit 2a820bf74918
("tracing: Use percpu stack trace buffer more intelligently").  Since
that commit, interrupts and NMIs do use the per-cpu stacks so the
comment is no longer correct.  Remove it.

(Note that the FTRACE_STACK_SIZE mentioned in the comment has never
existed, it probably should have said FTRACE_STACK_ENTRIES.)

Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>
---
 kernel/trace/trace.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index bb62269724d5..0a0fd197888c 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2932,12 +2932,6 @@ static void __ftrace_trace_stack(struct trace_buffer *buffer,
 		skip++;
 #endif
 
-	/*
-	 * Since events can happen in NMIs there's no safe way to
-	 * use the per cpu ftrace_stacks. We reserve it and if an interrupt
-	 * or NMI comes in, it will just have to use the default
-	 * FTRACE_STACK_SIZE.
-	 */
 	preempt_disable_notrace();
 
 	stackidx = __this_cpu_inc_return(ftrace_stack_reserve) - 1;
-- 
2.25.1