Re: [PATCH v22 01/13] trace-cmd: Find and store pids of tasks, which run virtual CPUs of given VM

[Steven Rostedt <rostedt@goodmis.org>]

On Wed,  4 Mar 2020 11:12:08 +0200
"Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com> wrote:

> +static int read_qemu_guests_pids(char *guest_task, struct guest *guest)
> +{
> +	struct dirent *entry;
> +	char path[PATH_MAX];
> +	char *buf = NULL;
> +	size_t n = 0;
> +	int ret = 0;
> +	long vcpu;
> +	long pid;
> +	DIR *dir;
> +	FILE *f;
> +
> +	snprintf(path, sizeof(path), "/proc/%s/task", guest_task);
> +	dir = opendir(path);
> +	if (!dir)
> +		return -1;
> +
> +	while (!ret && (entry = readdir(dir))) {
> +		if (!(entry->d_type == DT_DIR && is_digits(entry->d_name)))
> +			continue;
> +
> +		snprintf(path, sizeof(path), "/proc/%s/task/%s/comm",
> +			 guest_task, entry->d_name);
> +		f = fopen(path, "r");
> +		if (!f)
> +			continue;
> +
> +		if (getline(&buf, &n, f) >= 0 &&
> +		    strncmp(buf, "CPU ", 4) == 0) {
> +			vcpu = strtol(buf + 4, NULL, 10);
> +			pid = strtol(entry->d_name, NULL, 10);
> +			if (vcpu < INT_MAX && pid < INT_MAX &&
> +			    vcpu >= 0 && pid >= 0) {
> +				if (set_vcpu_pid_mapping(guest, vcpu, pid))
> +					ret = 1;

Small nit. For errors, I usually return negative numbers (positive numbers
are usually successful values). But unless there another issue with this
series, this is not big enough for a resend. I could always just patch it
as well.

-- Steve

> +			}
> +		}
> +
> +		fclose(f);
> +	}
> +	free(buf);
> +	return ret;
> +}