[PATCH v2 0/3] rtla: fix cgroup and trace options parsing

[PATCH v2 0/3] rtla: fix cgroup and trace options parsing

[Ivan Pravdin]

This series fixes 3 issue in rtla timerlat and osnoise parsing.

1. Fix buffer overflow when using --on-threshold option. Currently
   passing `--on-threshold trace` causes rtla timerlat to segfault.
   First patch addresses this issue.

2. Make -C/--cgroup option more user-friendly. Currently rtla timerlat
   and osnoise parses does not allow to specify tracer's threads cgroup
   name as `-C [cgroup]` or `--cgroup [cgroup]`. Second patch fixes this
   by allowing users to specify cgroup in the aforementioned manner.

3. When specifying `-t/--trace` before `-a/--auto`, trace filename is
   override to default <osnoise|timerlat>_trace.txt. For example, when
   running rtla as

       `rtla timerlat top -t custom_file.txt -a 100`

   when the threshold is reached, timerlat_trace.txt file is created
   instead of specified custom_file.txt. Third patch addresses this
   issue.

changes v1 -> v2:
   - Moved removing clear_terminal from `fix -C/--cgroup interface`
     patch to `fix -a overriding -t argument` patch
   - Added clarification why to remove clear_terminal
   - Added `Fixes:` tag to the `fix -C/--cgroup interface` patch

v1: https://lore.kernel.org/linux-trace-kernel/cover.1755014784.git.ipravdin.official@gmail.com/T/#t

Ivan Pravdin (3):
  rtla: fix buffer overflow in actions_parse
  rtla: fix -C/--cgroup interface
  rtla: fix -a overriding -t argument

 Documentation/tools/rtla/common_options.rst |  2 +-
 tools/tracing/rtla/src/actions.c            |  2 +-
 tools/tracing/rtla/src/osnoise_hist.c       | 25 +++++++++-----
 tools/tracing/rtla/src/osnoise_top.c        | 25 +++++++++-----
 tools/tracing/rtla/src/timerlat_hist.c      | 25 +++++++++-----
 tools/tracing/rtla/src/timerlat_top.c       | 37 +++++++++------------
 6 files changed, 66 insertions(+), 50 deletions(-)

-- 
2.48.1

[PATCH v2 1/3] rtla: fix buffer overflow in actions_parse

[Ivan Pravdin]

Currently, tests 3 and 13-22 in tests/timerlat.t fail with error:

    *** buffer overflow detected ***: terminated
    timeout: the monitored command dumped core

The result of running `sudo make check` is

    tests/timerlat.t (Wstat: 0 Tests: 22 Failed: 11)
      Failed tests:  3, 13-22
    Files=3, Tests=34, 140 wallclock secs ( 0.07 usr  0.01 sys + 27.63 cusr
    27.96 csys = 55.67 CPU)
    Result: FAIL

Fix buffer overflow in actions_parse to avoid this error. After this
change, the tests results are

    tests/hwnoise.t ... ok
    tests/osnoise.t ... ok
    tests/timerlat.t .. ok
    All tests successful.
    Files=3, Tests=34, 186 wallclock secs ( 0.06 usr  0.01 sys + 41.10 cusr
    44.38 csys = 85.55 CPU)
    Result: PASS

Fixes: 6ea082b171e0 ("rtla/timerlat: Add action on threshold feature")
Signed-off-by: Ivan Pravdin <ipravdin.official@gmail.com>
---
 tools/tracing/rtla/src/actions.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/tracing/rtla/src/actions.c b/tools/tracing/rtla/src/actions.c
index aaf0808125d7..eab51c0c0ce2 100644
--- a/tools/tracing/rtla/src/actions.c
+++ b/tools/tracing/rtla/src/actions.c
@@ -131,7 +131,7 @@ actions_parse(struct actions *self, const char *trigger)
 {
 	enum action_type type = ACTION_NONE;
 	char *token;
-	char trigger_c[strlen(trigger)];
+	char trigger_c[strlen(trigger) + 1];
 
 	/* For ACTION_SIGNAL */
 	int signal = 0, pid = 0;
-- 
2.48.1

[PATCH v2 2/3] rtla: fix -C/--cgroup interface

[Ivan Pravdin]

Currently, user can only specify cgroup to the tracer's thread the
following ways:

    `-C[cgroup]`
    `-C[=cgroup]`
    `--cgroup[=cgroup]`

If user tries to specify cgroup as `-C [cgroup]` or `--cgroup [cgroup]`,
the parser silently fails and rtla's cgroup is used for the tracer
threads.

To make interface more user-friendly, allow user to specify cgroup in
the aforementioned way, i.e. `-C [cgroup]` and `--cgroup [cgroup]`

Change documentation to reflect this user interface change.

Fixes: a957cbc02531 ("rtla: Add -C cgroup support")
Signed-off-by: Ivan Pravdin <ipravdin.official@gmail.com>
---
 Documentation/tools/rtla/common_options.rst |  2 +-
 tools/tracing/rtla/src/osnoise_hist.c       | 17 +++++++++++------
 tools/tracing/rtla/src/osnoise_top.c        | 17 +++++++++++------
 tools/tracing/rtla/src/timerlat_hist.c      | 17 +++++++++++------
 tools/tracing/rtla/src/timerlat_top.c       | 17 +++++++++++------
 5 files changed, 45 insertions(+), 25 deletions(-)

diff --git a/Documentation/tools/rtla/common_options.rst b/Documentation/tools/rtla/common_options.rst
index 2dc1575210aa..3f292a12b7af 100644
--- a/Documentation/tools/rtla/common_options.rst
+++ b/Documentation/tools/rtla/common_options.rst
@@ -42,7 +42,7 @@
         - *f:prio* - use SCHED_FIFO with *prio*;
         - *d:runtime[us|ms|s]:period[us|ms|s]* - use SCHED_DEADLINE with *runtime* and *period* in nanoseconds.
 
-**-C**, **--cgroup**\[*=cgroup*]
+**-C**, **--cgroup** \[*cgroup*]
 
         Set a *cgroup* to the tracer's threads. If the **-C** option is passed without arguments, the tracer's thread will inherit **rtla**'s *cgroup*. Otherwise, the threads will be placed on the *cgroup* passed to the option.
 
diff --git a/tools/tracing/rtla/src/osnoise_hist.c b/tools/tracing/rtla/src/osnoise_hist.c
index 8d579bcee709..298640d92434 100644
--- a/tools/tracing/rtla/src/osnoise_hist.c
+++ b/tools/tracing/rtla/src/osnoise_hist.c
@@ -435,7 +435,7 @@ static void osnoise_hist_usage(char *usage)
 		"	  -T/--threshold us: the minimum delta to be considered a noise",
 		"	  -c/--cpus cpu-list: list of cpus to run osnoise threads",
 		"	  -H/--house-keeping cpus: run rtla control threads only on the given cpus",
-		"	  -C/--cgroup[=cgroup_name]: set cgroup, if no cgroup_name is passed, the rtla's cgroup will be inherited",
+		"	  -C/--cgroup [cgroup_name]: set cgroup, if no cgroup_name is passed, the rtla's cgroup will be inherited",
 		"	  -d/--duration time[s|m|h|d]: duration of the session",
 		"	  -D/--debug: print debug info",
 		"	  -t/--trace[file]: save the stopped trace to [file|osnoise_trace.txt]",
@@ -559,12 +559,17 @@ static struct osnoise_params
 			break;
 		case 'C':
 			params->cgroup = 1;
-			if (!optarg) {
-				/* will inherit this cgroup */
+			if (optarg) {
+				if (optarg[0] == '=') {
+					/* skip the = */
+					params->cgroup_name = &optarg[1];
+				} else {
+					params->cgroup_name = optarg;
+				}
+			} else if (optind < argc && argv[optind][0] != '-') {
+				params->cgroup_name = argv[optind];
+			} else {
 				params->cgroup_name = NULL;
-			} else if (*optarg == '=') {
-				/* skip the = */
-				params->cgroup_name = ++optarg;
 			}
 			break;
 		case 'D':
diff --git a/tools/tracing/rtla/src/osnoise_top.c b/tools/tracing/rtla/src/osnoise_top.c
index 2c12780c8aa9..70924242bcdd 100644
--- a/tools/tracing/rtla/src/osnoise_top.c
+++ b/tools/tracing/rtla/src/osnoise_top.c
@@ -269,7 +269,7 @@ static void osnoise_top_usage(struct osnoise_params *params, char *usage)
 		"	  -T/--threshold us: the minimum delta to be considered a noise",
 		"	  -c/--cpus cpu-list: list of cpus to run osnoise threads",
 		"	  -H/--house-keeping cpus: run rtla control threads only on the given cpus",
-		"	  -C/--cgroup[=cgroup_name]: set cgroup, if no cgroup_name is passed, the rtla's cgroup will be inherited",
+		"	  -C/--cgroup [cgroup_name]: set cgroup, if no cgroup_name is passed, the rtla's cgroup will be inherited",
 		"	  -d/--duration time[s|m|h|d]: duration of the session",
 		"	  -D/--debug: print debug info",
 		"	  -t/--trace[file]: save the stopped trace to [file|osnoise_trace.txt]",
@@ -394,12 +394,17 @@ struct osnoise_params *osnoise_top_parse_args(int argc, char **argv)
 			break;
 		case 'C':
 			params->cgroup = 1;
-			if (!optarg) {
-				/* will inherit this cgroup */
+			if (optarg) {
+			if (optarg[0] == '=') {
+					/* skip the = */
+					params->cgroup_name = &optarg[1];
+				} else {
+					params->cgroup_name = optarg;
+				}
+			} else if (optind < argc && argv[optind][0] != '-') {
+				params->cgroup_name = argv[optind];
+			} else {
 				params->cgroup_name = NULL;
-			} else if (*optarg == '=') {
-				/* skip the = */
-				params->cgroup_name = ++optarg;
 			}
 			break;
 		case 'D':
diff --git a/tools/tracing/rtla/src/timerlat_hist.c b/tools/tracing/rtla/src/timerlat_hist.c
index 9baea1b251ed..2a48a076d941 100644
--- a/tools/tracing/rtla/src/timerlat_hist.c
+++ b/tools/tracing/rtla/src/timerlat_hist.c
@@ -726,7 +726,7 @@ static void timerlat_hist_usage(char *usage)
 		"	  -s/--stack us: save the stack trace at the IRQ if a thread latency is higher than the argument in us",
 		"	  -c/--cpus cpus: run the tracer only on the given cpus",
 		"	  -H/--house-keeping cpus: run rtla control threads only on the given cpus",
-		"	  -C/--cgroup[=cgroup_name]: set cgroup, if no cgroup_name is passed, the rtla's cgroup will be inherited",
+		"	  -C/--cgroup [cgroup_name]: set cgroup, if no cgroup_name is passed, the rtla's cgroup will be inherited",
 		"	  -d/--duration time[m|h|d]: duration of the session in seconds",
 		"	     --dump-tasks: prints the task running on all CPUs if stop conditions are met (depends on !--no-aa)",
 		"	  -D/--debug: print debug info",
@@ -885,12 +885,17 @@ static struct timerlat_params
 			break;
 		case 'C':
 			params->cgroup = 1;
-			if (!optarg) {
-				/* will inherit this cgroup */
+			if (optarg) {
+				if (optarg[0] == '=') {
+					/* skip the = */
+					params->cgroup_name = &optarg[1];
+				} else {
+					params->cgroup_name = optarg;
+				}
+			} else if (optind < argc && argv[optind][0] != '-') {
+				params->cgroup_name = argv[optind];
+			} else {
 				params->cgroup_name = NULL;
-			} else if (*optarg == '=') {
-				/* skip the = */
-				params->cgroup_name = ++optarg;
 			}
 			break;
 		case 'b':
diff --git a/tools/tracing/rtla/src/timerlat_top.c b/tools/tracing/rtla/src/timerlat_top.c
index c80b81c0b4da..e45d9978744c 100644
--- a/tools/tracing/rtla/src/timerlat_top.c
+++ b/tools/tracing/rtla/src/timerlat_top.c
@@ -492,7 +492,7 @@ static void timerlat_top_usage(char *usage)
 		"	  -s/--stack us: save the stack trace at the IRQ if a thread latency is higher than the argument in us",
 		"	  -c/--cpus cpus: run the tracer only on the given cpus",
 		"	  -H/--house-keeping cpus: run rtla control threads only on the given cpus",
-		"	  -C/--cgroup[=cgroup_name]: set cgroup, if no cgroup_name is passed, the rtla's cgroup will be inherited",
+		"	  -C/--cgroup [cgroup_name]: set cgroup, if no cgroup_name is passed, the rtla's cgroup will be inherited",
 		"	  -d/--duration time[s|m|h|d]: duration of the session",
 		"	  -D/--debug: print debug info",
 		"	     --dump-tasks: prints the task running on all CPUs if stop conditions are met (depends on !--no-aa)",
@@ -650,12 +650,17 @@ static struct timerlat_params
 			break;
 		case 'C':
 			params->cgroup = 1;
-			if (!optarg) {
-				/* will inherit this cgroup */
+			if (optarg) {
+				if (optarg[0] == '=') {
+					/* skip the = */
+					params->cgroup_name = &optarg[1];
+				} else {
+					params->cgroup_name = optarg;
+				}
+			} else if (optind < argc && argv[optind][0] != '-') {
+				params->cgroup_name = argv[optind];
+			} else {
 				params->cgroup_name = NULL;
-			} else if (*optarg == '=') {
-				/* skip the = */
-				params->cgroup_name = ++optarg;
 			}
 			break;
 		case 'D':
-- 
2.48.1

[PATCH v2 3/3] rtla: fix -a overriding -t argument

[Ivan Pravdin]

When running rtla as

    `rtla <timerlat|osnoise> <top|hist> -t custom_file.txt -a 100`

-a options override trace output filename specified by -t option.
Running the command above will create <timerlat|osnoise>_trace.txt file
instead of custom_file.txt. Fix this by making sure that -a option does
not override trace output filename even if it's passed after trace
output filename is specified.

Remove clear_terminal in timerlat top as it removes "Saving trace to <filename>"
line from the terminal and is not used in other modes.

Fixes: 173a3b014827 ("rtla/timerlat: Add the automatic trace option")
Signed-off-by: Ivan Pravdin <ipravdin.official@gmail.com>
---
 tools/tracing/rtla/src/osnoise_hist.c  |  8 +++++---
 tools/tracing/rtla/src/osnoise_top.c   |  8 +++++---
 tools/tracing/rtla/src/timerlat_hist.c |  8 +++++---
 tools/tracing/rtla/src/timerlat_top.c  | 20 +++++---------------
 4 files changed, 20 insertions(+), 24 deletions(-)

diff --git a/tools/tracing/rtla/src/osnoise_hist.c b/tools/tracing/rtla/src/osnoise_hist.c
index 298640d92434..53655bccbbad 100644
--- a/tools/tracing/rtla/src/osnoise_hist.c
+++ b/tools/tracing/rtla/src/osnoise_hist.c
@@ -543,7 +543,8 @@ static struct osnoise_params
 			params->threshold = 1;
 
 			/* set trace */
-			params->trace_output = "osnoise_trace.txt";
+			if (!params->trace_output)
+				params->trace_output = "osnoise_trace.txt";
 
 			break;
 		case 'b':
@@ -640,10 +641,11 @@ static struct osnoise_params
 					params->trace_output = &optarg[1];
 				else
 					params->trace_output = &optarg[0];
-			} else if (optind < argc && argv[optind][0] != '0')
+			} else if (optind < argc && argv[optind][0] != '0') {
 				params->trace_output = argv[optind];
-			else
+			} else {
 				params->trace_output = "osnoise_trace.txt";
+			}
 			break;
 		case '0': /* no header */
 			params->no_header = 1;
diff --git a/tools/tracing/rtla/src/osnoise_top.c b/tools/tracing/rtla/src/osnoise_top.c
index 70924242bcdd..db61a0c970e9 100644
--- a/tools/tracing/rtla/src/osnoise_top.c
+++ b/tools/tracing/rtla/src/osnoise_top.c
@@ -383,7 +383,8 @@ struct osnoise_params *osnoise_top_parse_args(int argc, char **argv)
 			params->threshold = 1;
 
 			/* set trace */
-			params->trace_output = "osnoise_trace.txt";
+			if (!params->trace_output)
+				params->trace_output = "osnoise_trace.txt";
 
 			break;
 		case 'c':
@@ -470,10 +471,11 @@ struct osnoise_params *osnoise_top_parse_args(int argc, char **argv)
 					params->trace_output = &optarg[1];
 				else
 					params->trace_output = &optarg[0];
-			} else if (optind < argc && argv[optind][0] != '-')
+			} else if (optind < argc && argv[optind][0] != '-') {
 				params->trace_output = argv[optind];
-			else
+			} else {
 				params->trace_output = "osnoise_trace.txt";
+			}
 			break;
 		case 'T':
 			params->threshold = get_llong_from_str(optarg);
diff --git a/tools/tracing/rtla/src/timerlat_hist.c b/tools/tracing/rtla/src/timerlat_hist.c
index 2a48a076d941..123b7f89f80a 100644
--- a/tools/tracing/rtla/src/timerlat_hist.c
+++ b/tools/tracing/rtla/src/timerlat_hist.c
@@ -874,7 +874,8 @@ static struct timerlat_params
 			params->print_stack = auto_thresh;
 
 			/* set trace */
-			trace_output = "timerlat_trace.txt";
+			if (!trace_output)
+				trace_output = "timerlat_trace.txt";
 
 			break;
 		case 'c':
@@ -972,10 +973,11 @@ static struct timerlat_params
 					trace_output = &optarg[1];
 				else
 					trace_output = &optarg[0];
-			} else if (optind < argc && argv[optind][0] != '-')
+			} else if (optind < argc && argv[optind][0] != '-') {
 				trace_output = argv[optind];
-			else
+			} else {
 				trace_output = "timerlat_trace.txt";
+			}
 			break;
 		case 'u':
 			params->user_workload = 1;
diff --git a/tools/tracing/rtla/src/timerlat_top.c b/tools/tracing/rtla/src/timerlat_top.c
index e45d9978744c..4d7c3d74ac50 100644
--- a/tools/tracing/rtla/src/timerlat_top.c
+++ b/tools/tracing/rtla/src/timerlat_top.c
@@ -423,15 +423,6 @@ timerlat_top_print_sum(struct osnoise_tool *top, struct timerlat_top_cpu *summar
 	}
 }
 
-/*
- * clear_terminal - clears the output terminal
- */
-static void clear_terminal(struct trace_seq *seq)
-{
-	if (!config_debug)
-		trace_seq_printf(seq, "\033c");
-}
-
 /*
  * timerlat_print_stats - print data for all cpus
  */
@@ -449,9 +440,6 @@ timerlat_print_stats(struct timerlat_params *params, struct osnoise_tool *top)
 	if (nr_cpus == -1)
 		nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
 
-	if (!params->quiet)
-		clear_terminal(trace->seq);
-
 	timerlat_top_reset_sum(&summary);
 
 	timerlat_top_header(params, top);
@@ -625,7 +613,8 @@ static struct timerlat_params
 			params->print_stack = auto_thresh;
 
 			/* set trace */
-			trace_output = "timerlat_trace.txt";
+			if (!trace_output)
+				trace_output = "timerlat_trace.txt";
 
 			break;
 		case '5':
@@ -729,10 +718,11 @@ static struct timerlat_params
 					trace_output = &optarg[1];
 				else
 					trace_output = &optarg[0];
-			} else if (optind < argc && argv[optind][0] != '-')
+			} else if (optind < argc && argv[optind][0] != '-') {
 				trace_output = argv[optind];
-			else
+			} else {
 				trace_output = "timerlat_trace.txt";
+			}
 			break;
 		case 'u':
 			params->user_workload = true;
-- 
2.48.1

Re: [PATCH v2 1/3] rtla: fix buffer overflow in actions_parse

[Tomas Glozar]

út 12. 8. 2025 v 19:21 odesílatel Ivan Pravdin
<ipravdin.official@gmail.com> napsal:
>
> Currently, tests 3 and 13-22 in tests/timerlat.t fail with error:
>
>     *** buffer overflow detected ***: terminated
>     timeout: the monitored command dumped core
>
> The result of running `sudo make check` is
>
>     tests/timerlat.t (Wstat: 0 Tests: 22 Failed: 11)
>       Failed tests:  3, 13-22
>     Files=3, Tests=34, 140 wallclock secs ( 0.07 usr  0.01 sys + 27.63 cusr
>     27.96 csys = 55.67 CPU)
>     Result: FAIL
>

Interestingly, I don't get this failure on my machine. Maybe due to
some compiler difference, the buffer overflow is not caught. Thank you
for the fix. Since the "signal" field is next to the buffer, and is
written after the strcpy, this might corrupt the PID number reading
for a command like:

$ rtla timerlat hist -D --on-threshold signal,num=2,pid=42

Reviewed-by: Tomas Glozar <tglozar@redhat.com>

Tomas

Re: [PATCH v2 2/3] rtla: fix -C/--cgroup interface

[Crystal Wood]

On Tue, 2025-08-12 at 13:21 -0400, Ivan Pravdin wrote:
> Currently, user can only specify cgroup to the tracer's thread the
> following ways:
> 
>     `-C[cgroup]`
>     `-C[=cgroup]`
>     `--cgroup[=cgroup]`
> 
> If user tries to specify cgroup as `-C [cgroup]` or `--cgroup [cgroup]`,
> the parser silently fails and rtla's cgroup is used for the tracer
> threads.
> 
> To make interface more user-friendly, allow user to specify cgroup in
> the aforementioned way, i.e. `-C [cgroup]` and `--cgroup [cgroup]`
> 
> Change documentation to reflect this user interface change.

I know these are the semantics that --trace implements, but they're
rather atypical... especially -C=group.


> @@ -559,12 +559,17 @@ static struct osnoise_params
>  			break;
>  		case 'C':
>  			params->cgroup = 1;
> -			if (!optarg) {
> -				/* will inherit this cgroup */
> +			if (optarg) {
> +				if (optarg[0] == '=') {
> +					/* skip the = */
> +					params->cgroup_name = &optarg[1];
> +				} else {
> +					params->cgroup_name = optarg;
> +				}
> +			} else if (optind < argc && argv[optind][0] != '-') {
> +				params->cgroup_name = argv[optind];
> +			} else {
>  				params->cgroup_name = NULL;
> -			} else if (*optarg == '=') {
> -				/* skip the = */
> -				params->cgroup_name = ++optarg;

If we're going to be consistently using these semantics, we should move
this logic into a utility function rather than open-coding it
everywhere.

Also, theoretically, shouldn't we be advancing optind for the case where
that's consumed?  Not that it matters much if we don't have positional
arguments once the options begin, and if we did, then allowing
"--arg optional-thing" would be ambiguous...

-Crystal

Re: [PATCH v2 3/3] rtla: fix -a overriding -t argument

[Tomas Glozar]

út 12. 8. 2025 v 19:22 odesílatel Ivan Pravdin
<ipravdin.official@gmail.com> napsal:
>
> When running rtla as
>
>     `rtla <timerlat|osnoise> <top|hist> -t custom_file.txt -a 100`
>
> -a options override trace output filename specified by -t option.
> Running the command above will create <timerlat|osnoise>_trace.txt file
> instead of custom_file.txt. Fix this by making sure that -a option does
> not override trace output filename even if it's passed after trace
> output filename is specified.
>

Yes, this should not be overridden, it's a bug in both the old
implementation and the new one using actions. Thank you for the fix.

> Remove clear_terminal in timerlat top as it removes "Saving trace to <filename>"
> line from the terminal and is not used in other modes.
>

This is not the correct fix for the issue. clear_terminal is needed in
timerlat top (and osnoise top) to clear the terminal before the
updated status is printed, the fix removes it without a replacement,
breaking this behavior. Also, this is a different issue that appeared
only when the actions patchset [1] was merged, and should go into a
separate patch with a different Fixes tag.

[1] https://lore.kernel.org/linux-trace-kernel/20250626123405.1496931-1-tglozar@redhat.com/T/#t

Tomas

Re: [PATCH v2 3/3] rtla: fix -a overriding -t argument

[Ivan Pravdin]

On Mon, Sep 01, 2025 at 04:23:55PM +0200, Tomas Glozar wrote:
> út 12. 8. 2025 v 19:22 odesílatel Ivan Pravdin
> <ipravdin.official@gmail.com> napsal:
> >
> > When running rtla as
> >
> >     `rtla <timerlat|osnoise> <top|hist> -t custom_file.txt -a 100`
> >
> > -a options override trace output filename specified by -t option.
> > Running the command above will create <timerlat|osnoise>_trace.txt file
> > instead of custom_file.txt. Fix this by making sure that -a option does
> > not override trace output filename even if it's passed after trace
> > output filename is specified.
> >
> 
> Yes, this should not be overridden, it's a bug in both the old
> implementation and the new one using actions. Thank you for the fix.
> 
> > Remove clear_terminal in timerlat top as it removes "Saving trace to <filename>"
> > line from the terminal and is not used in other modes.
> >
> 
> This is not the correct fix for the issue. clear_terminal is needed in
> timerlat top (and osnoise top) to clear the terminal before the
> updated status is printed, the fix removes it without a replacement,
> breaking this behavior. Also, this is a different issue that appeared
> only when the actions patchset [1] was merged, and should go into a
> separate patch with a different Fixes tag.
> 
> [1] https://lore.kernel.org/linux-trace-kernel/20250626123405.1496931-1-tglozar@redhat.com/T/#t

Makes sense. This problem indeed does not happend for osnoise. I will
update it in the next version of the patch.

> 
> Tomas
> 

	Ivan Pravdin

Re: [PATCH v2 2/3] rtla: fix -C/--cgroup interface

[Ivan Pravdin]

On Fri, Aug 29, 2025 at 02:12:28PM -0500, Crystal Wood wrote:
> On Tue, 2025-08-12 at 13:21 -0400, Ivan Pravdin wrote:
> > Currently, user can only specify cgroup to the tracer's thread the
> > following ways:
> > 
> >     `-C[cgroup]`
> >     `-C[=cgroup]`
> >     `--cgroup[=cgroup]`
> > 
> > If user tries to specify cgroup as `-C [cgroup]` or `--cgroup [cgroup]`,
> > the parser silently fails and rtla's cgroup is used for the tracer
> > threads.
> > 
> > To make interface more user-friendly, allow user to specify cgroup in
> > the aforementioned way, i.e. `-C [cgroup]` and `--cgroup [cgroup]`
> > 
> > Change documentation to reflect this user interface change.
> 
> I know these are the semantics that --trace implements, but they're
> rather atypical... especially -C=group.

The new semantics allow for -C [group] which is the same as -t
[filename] that has been fixed for -t/--trace.

> 
> > @@ -559,12 +559,17 @@ static struct osnoise_params
> >  			break;
> >  		case 'C':
> >  			params->cgroup = 1;
> > -			if (!optarg) {
> > -				/* will inherit this cgroup */
> > +			if (optarg) {
> > +				if (optarg[0] == '=') {
> > +					/* skip the = */
> > +					params->cgroup_name = &optarg[1];
> > +				} else {
> > +					params->cgroup_name = optarg;
> > +				}
> > +			} else if (optind < argc && argv[optind][0] != '-') {
> > +				params->cgroup_name = argv[optind];
> > +			} else {
> >  				params->cgroup_name = NULL;
> > -			} else if (*optarg == '=') {
> > -				/* skip the = */
> > -				params->cgroup_name = ++optarg;
> 
> If we're going to be consistently using these semantics, we should move
> this logic into a utility function rather than open-coding it
> everywhere.

Sure, I will move it into a utility function in the next version.
 
> Also, theoretically, shouldn't we be advancing optind for the case where
> that's consumed?  Not that it matters much if we don't have positional
> arguments once the options begin, and if we did, then allowing
> "--arg optional-thing" would be ambiguous...

It does seem that we should advance optind when optional argument is
provided. Good catch. I will fix it in the next version.

> -Crystal
> 

	Ivan Pravdin