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tracing: Clean up use of trace_create_maxlat_file()

PATCH In review Steven Rostedt 2 participants 3 messages Feb 8 Tracing

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Steven Rostedt

author maintainer
#0 lore raw

PATCH 1/1 tracing: Clean up use of trace_create_maxlat_file()

From: Steven Rostedt <[email protected]>

In trace.c, the function trace_create_maxlat_file() is defined behind the
#ifdef CONFIG_TRACER_MAX_TRACE block. The #else part defines it as:

 #define trace_create_maxlat_file(tr, d_tracer)				\
	trace_create_file("tracing_max_latency", TRACE_MODE_WRITE,	\
			  d_tracer, tr, &tracing_max_lat_fops)

But the one place that it it used has:

 #ifdef CONFIG_TRACER_MAX_TRACE
	trace_create_maxlat_file(tr, d_tracer);

#endif

Which is pointless and also wrong!

It only gets created when both CONFIG_TRACE_MAX_TRACE and CONFIG_FS_NOTIFY is defined, but the file itself should not be dependent on CONFIG_FS_NOTIFY. Always create that file when TRACE_MAX_TRACE is defined regardless if FS_NOTIFY is or is not.

Signed-off-by Steven Rostedt (Google) <[email protected]>

---
Changes since v2: https://patch.msgid.link/20260206230410.4ed96e9f@robin

- On further inspection, tracing_max_latency should always be created if CONFIG_TRACER_MAX_TRACE is defined regardless if CONFIG_FS_NOTIFY is.

 kernel/trace/trace.c | 38 ++++++++++++++++----------------------
 1 file changed, 16 insertions(+), 22 deletions(-)
kernel/trace/trace.c +16 -22
index 702ef851db45..d02c4004c718 100644
@@ -1912,10 +1912,7 @@ static ssize_t trace_seq_to_buffer(struct trace_seq *s, void *buf, size_t cnt)
 unsigned long __read_mostly	tracing_thresh;
 
 #ifdef CONFIG_TRACER_MAX_TRACE
-static const struct file_operations tracing_max_lat_fops;
-
 #ifdef LATENCY_FS_NOTIFY
-
 static struct workqueue_struct *fsnotify_wq;
 
 static void latency_fsnotify_workfn(struct work_struct *work)

@@ -1932,17 +1929,6 @@ static void latency_fsnotify_workfn_irq(struct irq_work *iwork)
 	queue_work(fsnotify_wq, &tr->fsnotify_work);
 }
 
-static void trace_create_maxlat_file(struct trace_array *tr,
-				     struct dentry *d_tracer)
-{
-	INIT_WORK(&tr->fsnotify_work, latency_fsnotify_workfn);
-	init_irq_work(&tr->fsnotify_irqwork, latency_fsnotify_workfn_irq);
-	tr->d_max_latency = trace_create_file("tracing_max_latency",
-					      TRACE_MODE_WRITE,
-					      d_tracer, tr,
-					      &tracing_max_lat_fops);
-}
-
 __init static int latency_fsnotify_init(void)
 {
 	fsnotify_wq = alloc_workqueue("tr_max_lat_wq",

@@ -1967,14 +1953,22 @@ void latency_fsnotify(struct trace_array *tr)
 	 */
 	irq_work_queue(&tr->fsnotify_irqwork);
 }
+#endif /* !LATENCY_FS_NOTIFY */
 
-#else /* !LATENCY_FS_NOTIFY */
-
-#define trace_create_maxlat_file(tr, d_tracer)				\
-	trace_create_file("tracing_max_latency", TRACE_MODE_WRITE,	\
-			  d_tracer, tr, &tracing_max_lat_fops)
+static const struct file_operations tracing_max_lat_fops;
 
+static void trace_create_maxlat_file(struct trace_array *tr,
+				     struct dentry *d_tracer)
+{
+#ifdef LATENCY_FS_NOTIFY
+	INIT_WORK(&tr->fsnotify_work, latency_fsnotify_workfn);
+	init_irq_work(&tr->fsnotify_irqwork, latency_fsnotify_workfn_irq);
 #endif
+	tr->d_max_latency = trace_create_file("tracing_max_latency",
+					      TRACE_MODE_WRITE,
+					      d_tracer, tr,
+					      &tracing_max_lat_fops);
+}
 
 /*
  * Copy the new maximum trace into the separate maximum-trace

@@ -2109,7 +2103,9 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)
 	__update_max_tr(tr, tsk, cpu);
 	arch_spin_unlock(&tr->max_lock);
 }
-
+#else /* !CONFIG_TRACER_MAX_TRACE */
+static inline void trace_create_maxlat_file(struct trace_array *tr,
+					    struct dentry *d_tracer) { }
 #endif /* CONFIG_TRACER_MAX_TRACE */
 
 struct pipe_wait {

@@ -10664,9 +10660,7 @@ init_tracer_tracefs(struct trace_array *tr, struct dentry *d_tracer)
 
 	create_trace_options_dir(tr);
 
-#ifdef CONFIG_TRACER_MAX_TRACE
 	trace_create_maxlat_file(tr, d_tracer);
-#endif
 
 	if (ftrace_create_function_files(tr, d_tracer))
 		MEM_FAIL(1, "Could not allocate function filter files");
Signature · 1 line
2.51.0
author maintainer
#1 lore raw

Was supposed to be "v3" in the subject.

-- Steve

build bot
#2 lore raw
In reply to Steven Rostedt
kernel test robot noticed the following build errors:

Hi Steven,

kernel test robot noticed the following build errors:

[auto build test ERROR on trace/for-next]
[also build test ERROR on linus/master v6.19-rc8 next-20260205] [If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Steven-Rostedt/tracing-Clean-up-use-of-trace_create_maxlat_file/20260208-081407
base:   https://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace for-next
patch link:    https://lore.kernel.org/r/20260207191101.0e014abd%40robin
patch subject: [PATCH] tracing: Clean up use of trace_create_maxlat_file()
config: arm-randconfig-r071-20260208 (https://download.01.org/0day-ci/archive/20260208/[email protected]/config)
compiler: arm-linux-gnueabi-gcc (GCC) 11.5.0
smatch version: v0.5.0-8994-gd50c5a4c
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260208/[email protected]/reproduce)

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 <[email protected]>
| Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/

All errors (new ones prefixed by >>):

kernel/trace/trace.c: In function 'trace_create_maxlat_file':

>> kernel/trace/trace.c:1967:13: error: 'struct trace_array' has no member named 'd_max_latency'; did you mean 'max_latency'?
    1967 |         tr->d_max_latency = trace_create_file("tracing_max_latency",
         |             ^~~~~~~~~~~~~
         |             max_latency

vim +1967 kernel/trace/trace.c

1959
1960 static void trace_create_maxlat_file(struct trace_array *tr,
1961 struct dentry *d_tracer)
1962 {
1963 #ifdef LATENCY_FS_NOTIFY
1964 INIT_WORK(&tr->fsnotify_work, latency_fsnotify_workfn);
1965 init_irq_work(&tr->fsnotify_irqwork, latency_fsnotify_workfn_irq);
1966 #endif

> 1967		tr->d_max_latency = trace_create_file("tracing_max_latency",
  1968						      TRACE_MODE_WRITE,
  1969						      d_tracer, tr,
  1970						      &tracing_max_lat_fops);

1971 }
1972

Signature · 2 lines
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki