rtla: Fix -C/--cgroup interface

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]`.

Refactor identical logic between -t/--trace and -C/--cgroup into a
common function.

Change documentation to reflect this user interface change.

Fixes: a957cbc02531 ("rtla: Add -C cgroup support")
Signed-off-by: Ivan Pravdin <ipravdin.official@gmail.com>
Reviewed-by: Tomas Glozar <tglozar@redhat.com>
Link: https://lore.kernel.org/r/16132f1565cf5142b5fbd179975be370b529ced7.1762186418.git.ipravdin.official@gmail.com
[ use capital letter in subject, as required by tracing subsystem ]
Signed-off-by: Tomas Glozar <tglozar@redhat.com>

1 files changed, 7 insertions, 19 deletions

diff --git a/tools/tracing/rtla/src/osnoise_hist.c b/tools/tracing/rtla/src/osnoise_hist.c
index 1d841a3056bc..1d06ea47b663 100644
--- a/tools/tracing/rtla/src/osnoise_hist.c
+++ b/tools/tracing/rtla/src/osnoise_hist.c
@@ -414,9 +414,9 @@ static void osnoise_hist_usage(void)
 	static const char * const msg[] = {
 		"",
 		"  usage: rtla osnoise hist [-h] [-D] [-d s] [-a us] [-p us] [-r us] [-s us] [-S us] \\",
-		"	  [-T us] [-t[file]] [-e sys[:event]] [--filter <filter>] [--trigger <trigger>] \\",
+		"	  [-T us] [-t [file]] [-e sys[:event]] [--filter <filter>] [--trigger <trigger>] \\",
 		"	  [-c cpu-list] [-H cpu-list] [-P priority] [-b N] [-E N] [--no-header] [--no-summary] \\",
-		"	  [--no-index] [--with-zeros] [-C[=cgroup_name]] [--warm-up]",
+		"	  [--no-index] [--with-zeros] [-C [cgroup_name]] [--warm-up]",
 		"",
 		"	  -h/--help: print this menu",
 		"	  -a/--auto: set automatic trace mode, stopping the session if argument in us sample is hit",
@@ -427,10 +427,10 @@ static void osnoise_hist_usage(void)
 		"	  -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]",
+		"	  -t/--trace [file]: save the stopped trace to [file|osnoise_trace.txt]",
 		"	  -e/--event <sys:event>: enable the <sys:event> in the trace instance, multiple -e are allowed",
 		"	     --filter <filter>: enable a trace event filter to the previous -e event",
 		"	     --trigger <trigger>: enable a trace event trigger to the previous -e event",
@@ -551,13 +551,7 @@ static struct common_params
 			break;
 		case 'C':
 			params->common.cgroup = 1;
-			if (!optarg) {
-				/* will inherit this cgroup */
-				params->common.cgroup_name = NULL;
-			} else if (*optarg == '=') {
-				/* skip the = */
-				params->common.cgroup_name = ++optarg;
-			}
+			params->common.cgroup_name = parse_optional_arg(argc, argv);
 			break;
 		case 'D':
 			config_debug = 1;
@@ -619,14 +613,8 @@ static struct common_params
 			params->threshold = get_llong_from_str(optarg);
 			break;
 		case 't':
-			if (optarg) {
-				if (optarg[0] == '=')
-					trace_output = &optarg[1];
-				else
-					trace_output = &optarg[0];
-			} else if (optind < argc && argv[optind][0] != '0')
-				trace_output = argv[optind];
-			else
+			trace_output = parse_optional_arg(argc, argv);
+			if (!trace_output)
 				trace_output = "osnoise_trace.txt";
 			break;
 		case '0': /* no header */