[LTP] [PATCH 2/3] Add process_mrelease01 test

[Cyril Hrubis]

Hi!
> +/*\
> + * [Description]
> + *
> + * This test verifies that process_mrelease() syscall is releasing memory from
> + * a killed process with memory allocation pending.
> + */
> +
> +#include "tst_test.h"
> +#include "lapi/syscalls.h"
> +
> +#define CHUNK (1 * TST_MB)
> +#define MAX_SIZE_MB (128 * TST_MB)
> +
> +static void *mem;
> +static volatile int *mem_size;
> +
> +static void do_child(int size)
> +{
> +	tst_res(TINFO, "Child: allocate %d bytes", size);
> +
> +	mem = SAFE_MMAP(NULL,
> +		size,
> +		PROT_READ | PROT_WRITE,
> +		MAP_PRIVATE | MAP_ANON,
> +		0, 0);

This does not actually alloate any memory, it set ups the vmas but the
actual memory is not allocated until you fault it by accessing it, so
you have to actually touch every page to get it faulted, e.g. memset()
it to something.


> +	TST_CHECKPOINT_WAKE_AND_WAIT(0);
> +
> +	tst_res(TINFO, "Child: releasing memory");
> +
> +	SAFE_MUNMAP(mem, size);
> +}
> +
> +static void run(void)
> +{
> +	int ret;
> +	int pidfd;
> +	int status;
> +	pid_t pid;
> +	volatile int restart;
> +
> +	for (*mem_size = CHUNK; *mem_size < MAX_SIZE_MB; *mem_size += CHUNK) {
> +		restart = 0;
> +
> +		pid = SAFE_FORK();
> +		if (!pid) {
> +			do_child(*mem_size);
> +			exit(0);
> +		}
> +
> +		TST_CHECKPOINT_WAIT(0);
> +		tst_disable_oom_protection(pid);

What is this needed for?

> +		pidfd = SAFE_PIDFD_OPEN(pid, 0);
> +
> +		tst_res(TINFO, "Parent: killing child with PID=%d", pid);
> +
> +		SAFE_KILL(pid, SIGKILL);
> +
> +		ret = tst_syscall(__NR_process_mrelease, pidfd, 0);
> +		if (ret == -1) {
> +			if (errno == ESRCH) {
> +				tst_res(TINFO, "Parent: child terminated before process_mrelease()."
> +					" Increase memory size and restart test");
> +
> +				restart = 1;

As far as I understand the documentation his condition should not happen
until you have called wait() on the process.

> +			} else {
> +				tst_res(TFAIL | TERRNO, "process_mrelease(%d,0) error", pidfd);
> +			}
> +		} else {
> +			tst_res(TPASS, "process_mrelease(%d,0) passed", pidfd);

Okay it passed, but did we free any memory?

Is the /proc/$pid/ still accessible before we wait on the killed
process? If it is we can parse the proc maps before and after
process_mrelease and check if the memory was really freed.

> +		}
> +
> +		SAFE_WAITPID(-1, &status, 0);
> +		SAFE_CLOSE(pidfd);
> +
> +		if (!restart)
> +			break;
> +	}
> +}
> +
> +static void setup(void)
> +{
> +	mem_size = SAFE_MMAP(
> +		NULL,
> +		sizeof(int),
> +		PROT_READ | PROT_WRITE,
> +		MAP_SHARED | MAP_ANONYMOUS,
> +		-1, 0);

Why do we keep the size in shared memory? The forked child has COW
access to the parent memory, we can use the variables set in the parent
just fine.

> +}
> +
> +static void cleanup(void)
> +{
> +	if (mem)
> +		SAFE_MUNMAP(mem, *mem_size);

This is allocated in chid and never non NULL in parent.

> +	if (mem_size)
> +		SAFE_MUNMAP((void *)mem_size, sizeof(int));
> +}
> +
> +static struct tst_test test = {
> +	.setup = setup,
> +	.cleanup = cleanup,
> +	.test_all = run,
> +	.needs_root = 1,
> +	.forks_child = 1,
> +	.min_kver = "5.15",
> +	.needs_checkpoints = 1,
> +	.needs_kconfigs = (const char *[]) {
> +		"CONFIG_MMU=y",
> +	},
> +};
> 
> -- 
> 2.35.3
> 
> 
> -- 
> Mailing list info: https://lists.linux.it/listinfo/ltp

-- 
Cyril Hrubis
chrubis@suse.cz