linux-kernel - [PATCH] ftrace: sample: avoid open-coded 64-bit division

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Message-Id: <20230130130246.247537-1-arnd@kernel.org>
Date:   Mon, 30 Jan 2023 14:02:37 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Cc:     Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org
Subject: [PATCH] ftrace: sample: avoid open-coded 64-bit division

From: Arnd Bergmann <arnd@...db.de>

Calculating the average period requires a 64-bit division that leads
to a link failure on 32-bit architectures:

x86_64-linux-ld: samples/ftrace/ftrace-ops.o: in function `ftrace_ops_sample_init':
ftrace-ops.c:(.init.text+0x23b): undefined reference to `__udivdi3'

Use the div_u64() helper to do this instead. Since this is an init function that
is not called frequently, the runtime overhead is going to be acceptable.

Fixes: b56c68f705ca ("ftrace: Add sample with custom ops")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 samples/ftrace/ftrace-ops.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/samples/ftrace/ftrace-ops.c b/samples/ftrace/ftrace-ops.c
index 24deb51c7261..0c8da87ff5c3 100644
--- a/samples/ftrace/ftrace-ops.c
+++ b/samples/ftrace/ftrace-ops.c
@@ -223,7 +223,7 @@ static int __init ftrace_ops_sample_init(void)
 
 	pr_info("Attempted %u calls to %ps in %lluns (%lluns / call)\n",
 		nr_function_calls, tracee_relevant,
-		period, period / nr_function_calls);
+		period, div_u64(period, nr_function_calls));
 
 	if (persist)
 		return 0;
-- 
2.39.0