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Date:   Fri, 18 Feb 2022 23:27:34 +0100
From:   Ismael Luceno <ismael@iodev.co.uk>
To:     "Dr. Thomas Orgis" <thomas.orgis@uni-hamburg.de>
Cc:     Balbir Singh <bsingharora@gmail.com>, linux-kernel@vger.kernel.org,
        hannes@cmpxchg.org
Subject: Re: [PATCH] taskstats: version 12 with thread group and exe info
Message-ID: <YhAdVhaCgD2rHRRz@pirotess>
References: <20220218185557.69aed9f0@cortex.rrz.uni-hamburg.de>
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On 18/Feb/2022 18:55, Dr. Thomas Orgis wrote:
> The task exit struct needs some cruciual information to be able
> to provide an enhanced version of process and thread accounting. This
> change provides:
> 
> 1. ac_tgid in additon to ac_pid
> 2. thread group execution walltime in ac_tgetime
> 3. flag AGROUP in ac_flag to indicate the last task
>    in a thread group / process
> 4. device ID and inode of task's /proc/self/exe in
>    ac_exe_dev and ac_exe_inode
> 5. tools/accounting/procacct as demonstrator
> 
> When a task exits, taskstats are reported to userspace including the
> task's pid and ppid, but without the id of the thread group this task
> is part of. Without the tgid, the stats of single tasks cannot be
> correlated to each other as a thread group (process).
> 
> The taskstats documentation suggests that on process exit a data set
> consisting of accumulated stats for the whole group is produced. But
> such an additional set of stats is only produced for actually
> multithreaded processes, not groups that had only one thread, and
> also those stats only contain data about delay accounting and not
> the more basic information about CPU and memory resource usage. Adding
> the AGROP flag to be set when the last task of a group exited enables
> determination of process end also for single-threaded processes.
> 
> My applicaton basically does enhanced process accounting with
> summed cputime, biggest maxrss, tasks per process. The data is not
> available with the traditional BSD process accounting (which is not
> designed to be extensible) and the taskstats interface allows more
> efficient on-the-fly grouping and summing of the stats, anyway,
> without intermediate disk writes.
> 
> Furthermore, I do carry statistics on which exact program binary
> is used how often with associated resources, getting a picture
> on how important which parts of a collection of installed scientific
> software in different versions are, and how well they put load on the
> machine. This is enabled by providing information on /proc/self/exe
> for each task. I assume the two 64-bit fields for device ID and
> inode are more appropriate than the possibly large resolved path
> to keep the data volume down.
> 
> Add the tgid to the stats to complete task identification,
> the flag AGROUP to mark the last task of a group, the group wallclock
> time, and inode-based identification of the associated executable file.
> 
> Add tools/accounting/procacct.c as a simplified fork of getdelays.c
> to demonstrate process and thread accounting.
> 
> Base-commit: b3d971ec25346d6890e9e8f05b63f758cfcef8c5
> 
> Signed-off-by: Dr. Thomas Orgis <thomas.orgis@uni-hamburg.de>
> ---
>  include/uapi/linux/acct.h      |   3 +-
>  include/uapi/linux/taskstats.h |  23 +-
>  kernel/taskstats.c             |  23 ++
>  kernel/tsacct.c                |  10 +-
>  tools/accounting/.gitignore    |   1 +
>  tools/accounting/Makefile      |   2 +-
>  tools/accounting/procacct.c    | 421 +++++++++++++++++++++++++++++++++
>  7 files changed, 476 insertions(+), 7 deletions(-)
>  create mode 100644 tools/accounting/procacct.c
> 
> diff --git a/include/uapi/linux/acct.h b/include/uapi/linux/acct.h
> index 985b89068591..0e591152aa8a 100644
> --- a/include/uapi/linux/acct.h
> +++ b/include/uapi/linux/acct.h
> @@ -103,12 +103,13 @@ struct acct_v3
>  /*
>   *  accounting flags
>   */
> -				/* bit set when the process ... */
> +				/* bit set when the process/task ... */
>  #define AFORK		0x01	/* ... executed fork, but did not exec */
>  #define ASU		0x02	/* ... used super-user privileges */
>  #define ACOMPAT		0x04	/* ... used compatibility mode (VAX only not used) */
>  #define ACORE		0x08	/* ... dumped core */
>  #define AXSIG		0x10	/* ... was killed by a signal */
> +#define AGROUP		0x20	/* ... was the last task of the process (task group) */
>  
>  #if defined(__BYTE_ORDER) ? __BYTE_ORDER == __BIG_ENDIAN : defined(__BIG_ENDIAN)
>  #define ACCT_BYTEORDER	0x80	/* accounting file is big endian */
> diff --git a/include/uapi/linux/taskstats.h b/include/uapi/linux/taskstats.h
> index 12327d32378f..957ab8f1424e 100644
> --- a/include/uapi/linux/taskstats.h
> +++ b/include/uapi/linux/taskstats.h
> @@ -34,7 +34,7 @@
>   */
>  
>  
> -#define TASKSTATS_VERSION	11
> +#define TASKSTATS_VERSION	12
>  #define TS_COMM_LEN		32	/* should be >= TASK_COMM_LEN
>  					 * in linux/sched.h */
>  
> @@ -48,7 +48,8 @@ struct taskstats {
>  	__u32	ac_exitcode;		/* Exit status */
>  
>  	/* The accounting flags of a task as defined in <linux/acct.h>
> -	 * Defined values are AFORK, ASU, ACOMPAT, ACORE, and AXSIG.
> +	 * Defined values are AFORK, ASU, ACOMPAT, ACORE, AXSIG, and AGROUP.
> +	 * (AGROUP since version 11).
>  	 */
>  	__u8	ac_flag;		/* Record flags */
>  	__u8	ac_nice;		/* task_nice */
> @@ -173,9 +174,25 @@ struct taskstats {
>  	/* v10: 64-bit btime to avoid overflow */
>  	__u64	ac_btime64;		/* 64-bit begin time */
>  
> -	/* Delay waiting for memory compact */
> +	/* v11: Delay waiting for memory compact */
>  	__u64	compact_count;
>  	__u64	compact_delay_total;
> +
> +	/* v12 begin */
> +	__u32   ac_tgid;	/* thread group ID */
> +	/* Thread group walltime up to now. This is total process walltime if
> +	 * AGROUP flag is set. */
> +	__u64	ac_tgetime __attribute__((aligned(8)));
> +	/* Lightweight information to identify process binary files.
> +	 * This leaves userspace to match this to a file system path, using
> +	 * MAJOR() and MINOR() macros to identify a device and mount point,
> +	 * the inode to identify the executable file. This is /proc/self/exe
> +	 * at the end, so matching the most recent exec(). Values are zero
> +	 * for kernel threads.
> +	 */
> +	__u64   ac_exe_dev;     /* program binary device ID */
> +	__u64   ac_exe_inode;   /* program binary inode number */
> +	/* v11 end */
>  };
>  
>  
> diff --git a/kernel/taskstats.c b/kernel/taskstats.c
> index 2b4898b4752e..55c532214ca3 100644
> --- a/kernel/taskstats.c
> +++ b/kernel/taskstats.c
> @@ -9,6 +9,7 @@
>  #include <linux/kernel.h>
>  #include <linux/taskstats_kern.h>
>  #include <linux/tsacct_kern.h>
> +#include <linux/acct.h>
>  #include <linux/delayacct.h>
>  #include <linux/cpumask.h>
>  #include <linux/percpu.h>
> @@ -152,6 +153,23 @@ static void send_cpu_listeners(struct sk_buff *skb,
>  	up_write(&listeners->sem);
>  }
>  
> +static void exe_add_tsk(struct taskstats *stats, struct task_struct *tsk)
> +{
> +	/* No idea if I'm allowed to access that here, now. */
> +	struct file *exe_file = get_task_exe_file(tsk);
> +
> +	if (exe_file) {
> +		/* Following cp_new_stat64() in stat.c . */
> +		stats->ac_exe_dev =
> +			huge_encode_dev(exe_file->f_inode->i_sb->s_dev);
> +		stats->ac_exe_inode = exe_file->f_inode->i_ino;
> +		fput(exe_file);
> +	} else {
> +		stats->ac_exe_dev = 0;
> +		stats->ac_exe_inode = 0;
> +	}
> +}
> +
>  static void fill_stats(struct user_namespace *user_ns,
>  		       struct pid_namespace *pid_ns,
>  		       struct task_struct *tsk, struct taskstats *stats)
> @@ -174,6 +192,9 @@ static void fill_stats(struct user_namespace *user_ns,
>  
>  	/* fill in extended acct fields */
>  	xacct_add_tsk(stats, tsk);
> +
> +	/* add executable info */
> +	exe_add_tsk(stats, tsk);
>  }
>  
>  static int fill_stats_for_pid(pid_t pid, struct taskstats *stats)
> @@ -619,6 +640,8 @@ void taskstats_exit(struct task_struct *tsk, int group_dead)
>  		goto err;
>  
>  	fill_stats(&init_user_ns, &init_pid_ns, tsk, stats);
> +	if(group_dead)
> +		stats->ac_flag |= AGROUP;
>  
>  	/*
>  	 * Doesn't matter if tsk is the leader or the last group member leaving
> diff --git a/kernel/tsacct.c b/kernel/tsacct.c
> index 1d261fbe367b..4252f0645b9e 100644
> --- a/kernel/tsacct.c
> +++ b/kernel/tsacct.c
> @@ -23,15 +23,20 @@ void bacct_add_tsk(struct user_namespace *user_ns,
>  {
>  	const struct cred *tcred;
>  	u64 utime, stime, utimescaled, stimescaled;
> -	u64 delta;
> +	u64 now_ns, delta;
>  	time64_t btime;
>  
>  	BUILD_BUG_ON(TS_COMM_LEN < TASK_COMM_LEN);
>  
>  	/* calculate task elapsed time in nsec */
> -	delta = ktime_get_ns() - tsk->start_time;
> +	now_ns = ktime_get_ns();
> +	/* store whole group time first */
> +	delta = now_ns - tsk->group_leader->start_time;
>  	/* Convert to micro seconds */
>  	do_div(delta, NSEC_PER_USEC);
> +	stats->ac_tgetime = delta;
> +	delta = now_ns - tsk->start_time;
> +	do_div(delta, NSEC_PER_USEC);
>  	stats->ac_etime = delta;
>  	/* Convert to seconds for btime (note y2106 limit) */
>  	btime = ktime_get_real_seconds() - div_u64(delta, USEC_PER_SEC);
> @@ -51,6 +56,7 @@ void bacct_add_tsk(struct user_namespace *user_ns,
>  	stats->ac_nice	 = task_nice(tsk);
>  	stats->ac_sched	 = tsk->policy;
>  	stats->ac_pid	 = task_pid_nr_ns(tsk, pid_ns);
> +	stats->ac_tgid   = task_tgid_nr_ns(tsk, pid_ns);
>  	rcu_read_lock();
>  	tcred = __task_cred(tsk);
>  	stats->ac_uid	 = from_kuid_munged(user_ns, tcred->uid);
> diff --git a/tools/accounting/.gitignore b/tools/accounting/.gitignore
> index c45fb4ed4309..522a690aaf3d 100644
> --- a/tools/accounting/.gitignore
> +++ b/tools/accounting/.gitignore
> @@ -1,2 +1,3 @@
>  # SPDX-License-Identifier: GPL-2.0-only
>  getdelays
> +procacct
> diff --git a/tools/accounting/Makefile b/tools/accounting/Makefile
> index 03687f19cbb1..11def1ad046c 100644
> --- a/tools/accounting/Makefile
> +++ b/tools/accounting/Makefile
> @@ -2,7 +2,7 @@
>  CC := $(CROSS_COMPILE)gcc
>  CFLAGS := -I../../usr/include
>  
> -PROGS := getdelays
> +PROGS := getdelays procacct
>  
>  all: $(PROGS)
>  
> diff --git a/tools/accounting/procacct.c b/tools/accounting/procacct.c
> new file mode 100644
> index 000000000000..8390d1251bc9
> --- /dev/null
> +++ b/tools/accounting/procacct.c
> @@ -0,0 +1,421 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* procacct.c
> + *
> + * Demonstrator of fetching resource data on task exit, as a way
> + * to accumulate accurate program resource usage statistics, without
> + * prior identification of the programs. For that, the fields for
> + * device and inode of the program executable binary file are also
> + * extracted in addition to the command string.
> + *
> + * The TGID together with the PID and the AGROUP flag allow
> + * identification of threads in a process and single-threaded processes.
> + * The ac_tgetime field gives proper whole-process walltime.
> + *
> + * Written (changed) by Thomas Orgis, University of Hamburg in 2022
> + *
> + * This is a cheap derivation (inheriting the style) of getdelays.c:
> + *
> + * Utility to get per-pid and per-tgid delay accounting statistics
> + * Also illustrates usage of the taskstats interface
> + *
> + * Copyright (C) Shailabh Nagar, IBM Corp. 2005
> + * Copyright (C) Balbir Singh, IBM Corp. 2006
> + * Copyright (c) Jay Lan, SGI. 2006
> + */
> +
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <errno.h>
> +#include <unistd.h>
> +#include <poll.h>
> +#include <string.h>
> +#include <fcntl.h>
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <sys/socket.h>
> +#include <sys/wait.h>
> +#include <signal.h>
> +
> +#include <linux/genetlink.h>
> +#include <linux/acct.h>
> +#include <linux/taskstats.h>
> +#include <linux/kdev_t.h>
> +
> +/*
> + * Generic macros for dealing with netlink sockets. Might be duplicated
> + * elsewhere. It is recommended that commercial grade applications use
> + * libnl or libnetlink and use the interfaces provided by the library
> + */
> +#define GENLMSG_DATA(glh)	((void *)(NLMSG_DATA(glh) + GENL_HDRLEN))
> +#define GENLMSG_PAYLOAD(glh)	(NLMSG_PAYLOAD(glh, 0) - GENL_HDRLEN)
> +#define NLA_DATA(na)		((void *)((char *)(na) + NLA_HDRLEN))
> +#define NLA_PAYLOAD(len)	(len - NLA_HDRLEN)
> +
> +#define err(code, fmt, arg...)			\
> +	do {					\
> +		fprintf(stderr, fmt, ##arg);	\
> +		exit(code);			\
> +	} while (0)
> +
> +int done;
> +int rcvbufsz;
> +char name[100];
> +int dbg;
> +int print_delays;
> +int print_io_accounting;
> +int print_task_context_switch_counts;
> +
> +#define PRINTF(fmt, arg...) {			\
> +		if (dbg) {			\
> +			printf(fmt, ##arg);	\
> +		}				\
> +	}
> +
> +/* Maximum size of response requested or message sent */
> +#define MAX_MSG_SIZE	1024
> +/* Maximum number of cpus expected to be specified in a cpumask */
> +#define MAX_CPUS	32
> +
> +struct msgtemplate {
> +	struct nlmsghdr n;
> +	struct genlmsghdr g;
> +	char buf[MAX_MSG_SIZE];
> +};
> +
> +char cpumask[100+6*MAX_CPUS];
> +
> +static void usage(void)
> +{
> +	fprintf(stderr, "procacct [-v] [-w logfile] [-r bufsize] [-m cpumask]\n");
> +	fprintf(stderr, "  -v: debug on\n");
> +}
> +
> +/*
> + * Create a raw netlink socket and bind
> + */
> +static int create_nl_socket(int protocol)
> +{
> +	int fd;
> +	struct sockaddr_nl local;
> +
> +	fd = socket(AF_NETLINK, SOCK_RAW, protocol);
> +	if (fd < 0)
> +		return -1;
> +
> +	if (rcvbufsz)
> +		if (setsockopt(fd, SOL_SOCKET, SO_RCVBUF,
> +				&rcvbufsz, sizeof(rcvbufsz)) < 0) {
> +			fprintf(stderr, "Unable to set socket rcv buf size to %d\n",
> +				rcvbufsz);
> +			goto error;
> +		}
> +
> +	memset(&local, 0, sizeof(local));
> +	local.nl_family = AF_NETLINK;
> +
> +	if (bind(fd, (struct sockaddr *) &local, sizeof(local)) < 0)
> +		goto error;
> +
> +	return fd;
> +error:
> +	close(fd);
> +	return -1;
> +}
> +
> +
> +static int send_cmd(int sd, __u16 nlmsg_type, __u32 nlmsg_pid,
> +	     __u8 genl_cmd, __u16 nla_type,
> +	     void *nla_data, int nla_len)
> +{
> +	struct nlattr *na;
> +	struct sockaddr_nl nladdr;
> +	int r, buflen;
> +	char *buf;
> +
> +	struct msgtemplate msg;
> +
> +	msg.n.nlmsg_len = NLMSG_LENGTH(GENL_HDRLEN);
> +	msg.n.nlmsg_type = nlmsg_type;
> +	msg.n.nlmsg_flags = NLM_F_REQUEST;
> +	msg.n.nlmsg_seq = 0;
> +	msg.n.nlmsg_pid = nlmsg_pid;
> +	msg.g.cmd = genl_cmd;
> +	msg.g.version = 0x1;
> +	na = (struct nlattr *) GENLMSG_DATA(&msg);
> +	na->nla_type = nla_type;
> +	na->nla_len = nla_len + 1 + NLA_HDRLEN;
> +	memcpy(NLA_DATA(na), nla_data, nla_len);
> +	msg.n.nlmsg_len += NLMSG_ALIGN(na->nla_len);
> +
> +	buf = (char *) &msg;
> +	buflen = msg.n.nlmsg_len;
> +	memset(&nladdr, 0, sizeof(nladdr));
> +	nladdr.nl_family = AF_NETLINK;
> +	while ((r = sendto(sd, buf, buflen, 0, (struct sockaddr *) &nladdr,
> +			   sizeof(nladdr))) < buflen) {
> +		if (r > 0) {
> +			buf += r;
> +			buflen -= r;
> +		} else if (errno != EAGAIN)
> +			return -1;
> +	}
> +	return 0;
> +}
> +
> +
> +/*
> + * Probe the controller in genetlink to find the family id
> + * for the TASKSTATS family
> + */
> +static int get_family_id(int sd)
> +{
> +	struct {
> +		struct nlmsghdr n;
> +		struct genlmsghdr g;
> +		char buf[256];
> +	} ans;
> +
> +	int id = 0, rc;
> +	struct nlattr *na;
> +	int rep_len;
> +
> +	strcpy(name, TASKSTATS_GENL_NAME);
> +	rc = send_cmd(sd, GENL_ID_CTRL, getpid(), CTRL_CMD_GETFAMILY,
> +			CTRL_ATTR_FAMILY_NAME, (void *)name,
> +			strlen(TASKSTATS_GENL_NAME)+1);
> +	if (rc < 0)
> +		return 0;	/* sendto() failure? */
> +
> +	rep_len = recv(sd, &ans, sizeof(ans), 0);
> +	if (ans.n.nlmsg_type == NLMSG_ERROR ||
> +	    (rep_len < 0) || !NLMSG_OK((&ans.n), rep_len))
> +		return 0;
> +
> +	na = (struct nlattr *) GENLMSG_DATA(&ans);
> +	na = (struct nlattr *) ((char *) na + NLA_ALIGN(na->nla_len));
> +	if (na->nla_type == CTRL_ATTR_FAMILY_ID)
> +		id = *(__u16 *) NLA_DATA(na);
> +
> +	return id;
> +}
> +
> +#define average_ms(t, c) (t / 1000000ULL / (c ? c : 1))
> +
> +static void print_procacct(struct taskstats *t)
> +{
> +	printf( /* First letter: T is a mere thread, G the last in a group, U  unknown. */
> +		"%c pid=%lu tgid=%lu uid=%lu wall=%llu gwall=%llu cpu=%llu vmpeak=%llu rsspeak=%llu"
> +		" dev=%llu:%llu inode=%llu comm=%s\n"
> +	,	t->version >= 12 ? (t->ac_flag & AGROUP ? 'P' : 'T') : '?'
> +	,	(unsigned long)t->ac_pid
> +	,	(unsigned long)(t->version >= 12 ? t->ac_tgid : 0)
> +	,	(unsigned long)t->ac_uid
> +	,	(unsigned long long)t->ac_etime
> +	,	(unsigned long long)(t->version >= 12 ? t->ac_tgetime : 0)
> +	,	(unsigned long long)(t->ac_utime+t->ac_stime)
> +	,	(unsigned long long)t->hiwater_vm
> +	,	(unsigned long long)t->hiwater_rss
> +	,	(unsigned long)(t->version >= 12 ? MAJOR(t->ac_exe_dev) : 0)
> +	,	(unsigned long)(t->version >= 12 ? MINOR(t->ac_exe_dev) : 0)
> +	,	(unsigned long long)(t->version >= 12 ? t->ac_exe_inode : 0)
> +	,	t->ac_comm
> +	);
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +	int c, rc, rep_len, aggr_len, len2;
> +	int cmd_type = TASKSTATS_CMD_ATTR_UNSPEC;
> +	__u16 id;
> +	__u32 mypid;
> +
> +	struct nlattr *na;
> +	int nl_sd = -1;
> +	int len = 0;
> +	pid_t tid = 0;
> +	pid_t rtid = 0;
> +
> +	int fd = 0;
> +	int count = 0;
> +	int write_file = 0;
> +	int maskset = 0;
> +	char *logfile = NULL;
> +	int loop = 1;
> +	int containerset = 0;
> +	char *containerpath = NULL;
> +	int cfd = 0;
> +	int forking = 0;
> +	sigset_t sigset;
> +
> +	struct msgtemplate msg;
> +
> +	while (!forking) {
> +		c = getopt(argc, argv, "m:vr:");
> +		if (c < 0)
> +			break;
> +
> +		switch (c) {
> +		case 'w':
> +			logfile = strdup(optarg);
> +			printf("write to file %s\n", logfile);
> +			write_file = 1;
> +			break;
> +		case 'r':
> +			rcvbufsz = atoi(optarg);
> +			printf("receive buf size %d\n", rcvbufsz);
> +			if (rcvbufsz < 0)
> +				err(1, "Invalid rcv buf size\n");
> +			break;
> +		case 'm':
> +			strncpy(cpumask, optarg, sizeof(cpumask));
> +			cpumask[sizeof(cpumask) - 1] = '\0';
> +			maskset = 1;
> +			break;
> +		case 'v':
> +			printf("debug on\n");
> +			dbg = 1;
> +			break;
> +		default:
> +			usage();
> +			exit(-1);
> +		}
> +	}
> +	if (!maskset) {
> +		maskset = 1;
> +		strncpy(cpumask, "1", sizeof(cpumask));
> +		cpumask[sizeof(cpumask) - 1] = '\0';
> +	}
> +	printf("cpumask %s maskset %d\n", cpumask, maskset);
> +
> +	if (write_file) {
> +		fd = open(logfile, O_WRONLY | O_CREAT | O_TRUNC, 0644);
> +		if (fd == -1) {
> +			perror("Cannot open output file\n");
> +			exit(1);
> +		}
> +	}
> +
> +	nl_sd = create_nl_socket(NETLINK_GENERIC);
> +	if (nl_sd < 0)
> +		err(1, "error creating Netlink socket\n");
> +
> +	mypid = getpid();
> +	id = get_family_id(nl_sd);
> +	if (!id) {
> +		fprintf(stderr, "Error getting family id, errno %d\n", errno);
> +		goto err;
> +	}
> +	PRINTF("family id %d\n", id);
> +
> +	if (maskset) {
> +		rc = send_cmd(nl_sd, id, mypid, TASKSTATS_CMD_GET,
> +			      TASKSTATS_CMD_ATTR_REGISTER_CPUMASK,
> +			      &cpumask, strlen(cpumask) + 1);
> +		PRINTF("Sent register cpumask, retval %d\n", rc);
> +		if (rc < 0) {
> +			fprintf(stderr, "error sending register cpumask\n");
> +			goto err;
> +		}
> +	}
> +
> +	do {
> +		rep_len = recv(nl_sd, &msg, sizeof(msg), 0);
> +		PRINTF("received %d bytes\n", rep_len);
> +
> +		if (rep_len < 0) {
> +			fprintf(stderr, "nonfatal reply error: errno %d\n",
> +				errno);
> +			continue;
> +		}
> +		if (msg.n.nlmsg_type == NLMSG_ERROR ||
> +		    !NLMSG_OK((&msg.n), rep_len)) {
> +			struct nlmsgerr *err = NLMSG_DATA(&msg);
> +
> +			fprintf(stderr, "fatal reply error,  errno %d\n",
> +				err->error);
> +			goto done;
> +		}
> +
> +		PRINTF("nlmsghdr size=%zu, nlmsg_len=%d, rep_len=%d\n",
> +		       sizeof(struct nlmsghdr), msg.n.nlmsg_len, rep_len);
> +
> +
> +		rep_len = GENLMSG_PAYLOAD(&msg.n);
> +
> +		na = (struct nlattr *) GENLMSG_DATA(&msg);
> +		len = 0;
> +		while (len < rep_len) {
> +			len += NLA_ALIGN(na->nla_len);
> +			int mother = na->nla_type;
> +
> +			PRINTF("mother=%i\n", mother);
> +			switch (na->nla_type) {
> +			case TASKSTATS_TYPE_AGGR_PID:
> +				/* Fall through */
> +			case TASKSTATS_TYPE_AGGR_TGID:
> +				aggr_len = NLA_PAYLOAD(na->nla_len);
> +				len2 = 0;
> +				/* For nested attributes, na follows */
> +				na = (struct nlattr *) NLA_DATA(na);
> +				done = 0;
> +				while (len2 < aggr_len) {
> +					switch (na->nla_type) {
> +					case TASKSTATS_TYPE_PID:
> +						rtid = *(int *) NLA_DATA(na);
> +						PRINTF("PID\t%d\n", rtid);
> +						break;
> +					case TASKSTATS_TYPE_TGID:
> +						rtid = *(int *) NLA_DATA(na);
> +						PRINTF("TGID\t%d\n", rtid);
> +						break;
> +					case TASKSTATS_TYPE_STATS:
> +						count++;
> +						if (mother == TASKSTATS_TYPE_AGGR_PID)
> +							print_procacct((struct taskstats *) NLA_DATA(na));
> +						if (fd) {
> +							if (write(fd, NLA_DATA(na), na->nla_len) < 0)
> +								err(1, "write error\n");
> +						}
> +						if (!loop)
> +							goto done;
> +						break;
> +					case TASKSTATS_TYPE_NULL:
> +						break;
> +					default:
> +						fprintf(stderr, "Unknown nested"
> +							" nla_type %d\n",
> +							na->nla_type);
> +						break;
> +					}
> +					len2 += NLA_ALIGN(na->nla_len);
> +					na = (struct nlattr *)((char *)na +
> +							       NLA_ALIGN(na->nla_len));
> +				}
> +				break;
> +
> +			default:
> +				fprintf(stderr, "Unexpected nla_type %d\n",
> +					na->nla_type);
> +			case TASKSTATS_TYPE_NULL:
> +				break;
> +			}
> +			na = (struct nlattr *) (GENLMSG_DATA(&msg) + len);
> +		}
> +	} while (loop);
> +done:
> +	if (maskset) {
> +		rc = send_cmd(nl_sd, id, mypid, TASKSTATS_CMD_GET,
> +			      TASKSTATS_CMD_ATTR_DEREGISTER_CPUMASK,
> +			      &cpumask, strlen(cpumask) + 1);
> +		printf("Sent deregister mask, retval %d\n", rc);
> +		if (rc < 0)
> +			err(rc, "error sending deregister cpumask\n");
> +	}
> +err:
> +	close(nl_sd);
> +	if (fd)
> +		close(fd);
> +	if (cfd)
> +		close(cfd);
> +	return 0;
> +}
> -- 
> 2.35.0
> 

Reviewed-by: Ismael Luceno <ismael@iodev.co.uk>