linux-kernel - [PATCH 2/6] tools/rtla: Fix uninitialized bucket/data->bucket

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Message-ID: <6e1b1665cd99042ae705b3e0fc410858c4c42346.1707217097.git.bristot@kernel.org>
Date: Tue,  6 Feb 2024 12:05:30 +0100
From: Daniel Bristot de Oliveira <bristot@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Daniel Bristot de Oliveira <bristot@...nel.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Donald Zickus <dzickus@...hat.com>,
	stable@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev
Subject: [PATCH 2/6] tools/rtla: Fix uninitialized bucket/data->bucket_size warning

When compiling rtla with clang, I am getting the following warnings:

$ make HOSTCC=clang CC=clang LLVM_IAS=1

[..]
clang -O -g -DVERSION=\"6.8.0-rc3\" -flto=auto -fexceptions
	-fstack-protector-strong -fasynchronous-unwind-tables
	-fstack-clash-protection  -Wall -Werror=format-security
	-Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS
	$(pkg-config --cflags libtracefs)
	-c -o src/osnoise_hist.o src/osnoise_hist.c
src/osnoise_hist.c:138:6: warning: variable 'bucket' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
  138 |         if (data->bucket_size)
      |             ^~~~~~~~~~~~~~~~~
src/osnoise_hist.c:149:6: note: uninitialized use occurs here
  149 |         if (bucket < entries)
      |             ^~~~~~
src/osnoise_hist.c:138:2: note: remove the 'if' if its condition is always true
  138 |         if (data->bucket_size)
      |         ^~~~~~~~~~~~~~~~~~~~~~
  139 |                 bucket = duration / data->bucket_size;
src/osnoise_hist.c:132:12: note: initialize the variable 'bucket' to silence this warning
  132 |         int bucket;
      |                   ^
      |                    = 0
1 warning generated.

[...]

clang -O -g -DVERSION=\"6.8.0-rc3\" -flto=auto -fexceptions
	-fstack-protector-strong -fasynchronous-unwind-tables
	-fstack-clash-protection  -Wall -Werror=format-security
	-Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS
	$(pkg-config --cflags libtracefs)
	-c -o src/timerlat_hist.o src/timerlat_hist.c
src/timerlat_hist.c:181:6: warning: variable 'bucket' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
  181 |         if (data->bucket_size)
      |             ^~~~~~~~~~~~~~~~~
src/timerlat_hist.c:204:6: note: uninitialized use occurs here
  204 |         if (bucket < entries)
      |             ^~~~~~
src/timerlat_hist.c:181:2: note: remove the 'if' if its condition is always true
  181 |         if (data->bucket_size)
      |         ^~~~~~~~~~~~~~~~~~~~~~
  182 |                 bucket = latency / data->bucket_size;
src/timerlat_hist.c:175:12: note: initialize the variable 'bucket' to silence this warning
  175 |         int bucket;
      |                   ^
      |                    = 0
1 warning generated.

This is a legit warning, but data->bucket_size is always > 0 (see
timerlat_hist_parse_args()), so the if is not necessary.

Remove the unneeded if (data->bucket_size) to avoid the warning.

Cc: stable@...r.kernel.org
Fixes: 1eeb6328e8b3 ("rtla/timerlat: Add timerlat hist mode")
Fixes: 829a6c0b5698 ("rtla/osnoise: Add the hist mode")
Signed-off-by: Daniel Bristot de Oliveira <bristot@...nel.org>
---
 tools/tracing/rtla/src/osnoise_hist.c  | 3 +--
 tools/tracing/rtla/src/timerlat_hist.c | 3 +--
 2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/tools/tracing/rtla/src/osnoise_hist.c b/tools/tracing/rtla/src/osnoise_hist.c
index 8f81fa007364..67128171c29d 100644
--- a/tools/tracing/rtla/src/osnoise_hist.c
+++ b/tools/tracing/rtla/src/osnoise_hist.c
@@ -135,8 +135,7 @@ static void osnoise_hist_update_multiple(struct osnoise_tool *tool, int cpu,
 	if (params->output_divisor)
 		duration = duration / params->output_divisor;
 
-	if (data->bucket_size)
-		bucket = duration / data->bucket_size;
+	bucket = duration / data->bucket_size;
 
 	total_duration = duration * count;
 
diff --git a/tools/tracing/rtla/src/timerlat_hist.c b/tools/tracing/rtla/src/timerlat_hist.c
index 47d3d8b53cb2..3a5b8c409e7d 100644
--- a/tools/tracing/rtla/src/timerlat_hist.c
+++ b/tools/tracing/rtla/src/timerlat_hist.c
@@ -178,8 +178,7 @@ timerlat_hist_update(struct osnoise_tool *tool, int cpu,
 	if (params->output_divisor)
 		latency = latency / params->output_divisor;
 
-	if (data->bucket_size)
-		bucket = latency / data->bucket_size;
+	bucket = latency / data->bucket_size;
 
 	if (!context) {
 		hist = data->hist[cpu].irq;
-- 
2.43.0