linux-kernel - Re: [PATCH 3/5] tracing: Have tracer option be instance specific

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Message-ID: <202511071533.domGENBS-lkp@intel.com>
Date: Mon, 5 Jan 2026 18:23:31 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: oe-kbuild@...ts.linux.dev, Steven Rostedt <rostedt@...dmis.org>,
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Cc: lkp@...el.com, oe-kbuild-all@...ts.linux.dev,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Memory Management List <linux-mm@...ck.org>
Subject: Re: [PATCH 3/5] tracing: Have tracer option be instance specific

Hi Steven,

kernel test robot noticed the following build warnings:

https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Steven-Rostedt/tracing-Remove-dummy-options-and-flags/20251106-010511
base:   https://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace for-next
patch link:    https://lore.kernel.org/r/20251105161935.545400234%40kernel.org
patch subject: [PATCH 3/5] tracing: Have tracer option be instance specific
config: i386-randconfig-r072-20251107 (https://download.01.org/0day-ci/archive/20251107/202511071533.domGENBS-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@...el.com>
| Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
| Closes: https://lore.kernel.org/r/202511071533.domGENBS-lkp@intel.com/

smatch warnings:
kernel/trace/trace.c:6313 tracing_set_tracer() warn: iterator used outside loop: 't'

vim +/t +6313 kernel/trace/trace.c

9c5b9d3d65e4858 Masami Hiramatsu         2020-01-11  6285  int tracing_set_tracer(struct trace_array *tr, const char *buf)
09d23a1d8a82e81 Steven Rostedt (Red Hat  2015-02-03  6286) {
4699bbb369ba1d3 Steven Rostedt           2025-11-05  6287  	struct tracer *trace;
4699bbb369ba1d3 Steven Rostedt           2025-11-05  6288  	struct tracers *t;
12883efb670c28d Steven Rostedt (Red Hat  2013-03-05  6289) #ifdef CONFIG_TRACER_MAX_TRACE
34600f0e9c33c9c Steven Rostedt           2013-01-22  6290  	bool had_max_tr;
12883efb670c28d Steven Rostedt (Red Hat  2013-03-05  6291) #endif
d33b10c0c73adca Steven Rostedt           2024-12-24  6292  	int ret;
bc0c38d139ec7fc Steven Rostedt           2008-05-12  6293  
d33b10c0c73adca Steven Rostedt           2024-12-24  6294  	guard(mutex)(&trace_types_lock);
1027fcb206a0fb8 Steven Rostedt           2009-03-12  6295  
7a1d1e4b9639ff0 Steven Rostedt (Google   2024-06-12  6296) 	update_last_data(tr);
7a1d1e4b9639ff0 Steven Rostedt (Google   2024-06-12  6297) 
a1f157c7a3bb342 Zheng Yejian             2023-09-06  6298  	if (!tr->ring_buffer_expanded) {
2b6080f28c7cc3e Steven Rostedt           2012-05-11  6299  		ret = __tracing_resize_ring_buffer(tr, trace_buf_size,
438ced1720b5840 Vaibhav Nagarnaik        2012-02-02  6300  						RING_BUFFER_ALL_CPUS);
73c5162aa362a54 Steven Rostedt           2009-03-11  6301  		if (ret < 0)
d33b10c0c73adca Steven Rostedt           2024-12-24  6302  			return ret;
73c5162aa362a54 Steven Rostedt           2009-03-11  6303  		ret = 0;
73c5162aa362a54 Steven Rostedt           2009-03-11  6304  	}
73c5162aa362a54 Steven Rostedt           2009-03-11  6305  
4699bbb369ba1d3 Steven Rostedt           2025-11-05  6306  	list_for_each_entry(t, &tr->tracers, list) {
4699bbb369ba1d3 Steven Rostedt           2025-11-05  6307  		if (strcmp(t->tracer->name, buf) == 0)
bc0c38d139ec7fc Steven Rostedt           2008-05-12  6308  			break;
bc0c38d139ec7fc Steven Rostedt           2008-05-12  6309  	}
d33b10c0c73adca Steven Rostedt           2024-12-24  6310  	if (!t)

t can't be NULL here.  It needs to be if (list_entry_is_head()) return;

d33b10c0c73adca Steven Rostedt           2024-12-24  6311  		return -EINVAL;
d33b10c0c73adca Steven Rostedt           2024-12-24  6312  
4699bbb369ba1d3 Steven Rostedt           2025-11-05 @6313  	if (t->tracer == tr->current_trace)
d33b10c0c73adca Steven Rostedt           2024-12-24  6314  		return 0;
bc0c38d139ec7fc Steven Rostedt           2008-05-12  6315  
4699bbb369ba1d3 Steven Rostedt           2025-11-05  6316  	trace = t->tracer;
4699bbb369ba1d3 Steven Rostedt           2025-11-05  6317  

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki