[LTP] cgroup: Add cgroup_burst01 test

[linuxtestproject.agent@gmail.com]

Hi Samir,

On Mon, 28 Sep 2026 07:17:34 +0200, Samir Mulani wrote:
> cgroup: Add cgroup_burst01 test

--- [PATCH 1/2] ---

> cgroup: Add cgroup_burst01 test

The test and binary name is cpu_max_burst01. Update the subject line
to match the test name.

>   TC3 - A worker underruns to build up burst credit, then overloads
>         to consume it; cpu.stat nr_bursts and burst_usec counters
>         must increase. Also checks that burst can be updated while
>         tasks are running.

The test code never updates cpu.max.burst while tasks are running.
Update the commit message or add the missing check to the test.

> diff --git a/runtest/controllers b/runtest/controllers
> --- a/runtest/controllers
> +++ b/runtest/controllers
> @@ -3,6 +3,7 @@ cgroup_core01	cgroup_core01
>  cgroup_core02	cgroup_core02
>  cgroup_core03	cgroup_core03
>  cgroup		cgroup_regression_test.sh
> +cpu_max_burst01  cpu_max_burst01

Use a tab character instead of spaces between the test name and the
binary path.

>  * Test scenarios:
>  *   TC 1 - Default value and write-zero: cpu.max.burst defaults to 0;

Insert a blank line before the list in the documentation comment block.

> 		if (err != EINVAL) {
> 			tst_res(TWARN,
> 				"tc2_burst_exceeds_quota: got errno=%d (%s), expected EINVAL",
> 				err, tst_strerrno(err));
> 		}
> 
> 		if (burst != BURST_US) {
> 			tst_res(TFAIL,
> 				"tc2_burst_exceeds_quota: burst corrupted after rejected write (expected %llu us, got %llu us)",
> 				BURST_US, burst);
> 		} else {
> 			tst_res(TPASS,
> 				"tc2_burst_exceeds_quota: burst=%llu rejected (errno=%d), stored value unchanged (%llu us)",
> 				bad_burst, err, burst);
> 		}

If err != EINVAL, report TFAIL instead of TWARN. As written, receiving an
unexpected errno still reports TPASS when burst remains unchanged.

> 	read_burst_stat(cg_child, &after);

Check the return value of read_burst_stat(). If reading cpu.stat fails,
abort with TBROK rather than proceeding with zeroed stats to TFAIL.

> 	if (cmd_pipe[1] >= 0) {
> 		SAFE_CLOSE(cmd_pipe[1]);
> 		cmd_pipe[1] = -1;
> 	}
> 	if (ack_pipe[0] >= 0) {
> 		SAFE_CLOSE(ack_pipe[0]);
> 		ack_pipe[0] = -1;
> 	}

Use '!= -1' instead of '>= 0' to check file descriptor validity.

--- [PATCH 2/2] ---

> cgroup: Add invalid burst test

Name the test explicitly in the subject line (e.g. cgroup: Add
cpu_max_burst_invalid01 test).

> diff --git a/runtest/controllers b/runtest/controllers
> --- a/runtest/controllers
> +++ b/runtest/controllers
> @@ -4,6 +4,7 @@ cgroup_core02	cgroup_core02
>  cgroup_core03	cgroup_core03
>  cgroup		cgroup_regression_test.sh
>  cpu_max_burst01  cpu_max_burst01
> +cpu_max_burst_invalid01  cpu_max_burst_invalid01

Use a tab character instead of spaces between the test name and the
binary path.

>  * Test scenarios:
>  *   TC 1 - Boundary and sign violations: burst = quota+1 (B) and burst = "-1"

Insert a blank line before the list in the documentation comment block.

> /* MAX_BW_US: kernel max_bw_runtime_us = (1 << BW_SHIFT) * USEC_PER_SEC */
> #define MAX_BW_US	(((uint64_t)1 << 20) * 1000000ULL)

The kernel defines MAX_BW as ((1ULL << (64 - BW_SHIFT)) - 1), which is
(1ULL << 44) - 1. The current calculation is too small and does not exceed
the kernel limit, causing tc2 to always take the TCONF fallback path.

> static int cg_write_str(const struct tst_cg_group *cg,
> 			const char *fname, const char *str)
> {
> 	int fd, saved = 0;
> 	ssize_t n;
> 
> 	fd = SAFE_OPENAT(cg_dirfd(cg), fname, O_WRONLY);
> 	n  = write(fd, str, strlen(str));

Use TST_EXP_FAIL2(write(...), EINVAL) rather than calling bare write()
and propagating errno through helper return values.

Verdict - Needs revision

---
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