8 files changed, 646 insertions, 0 deletions

diff --git a/Documentation/accounting/taskstats.txt b/Documentation/accounting/taskstats.txt
new file mode 100644
index 000000000000..ad9b6997e162
--- /dev/null
+++ b/Documentation/accounting/taskstats.txt
@@ -0,0 +1,146 @@
+Per-task statistics interface
+-----------------------------
+
+
+Taskstats is a netlink-based interface for sending per-task and
+per-process statistics from the kernel to userspace.
+
+Taskstats was designed for the following benefits:
+
+- efficiently provide statistics during lifetime of a task and on its exit
+- unified interface for multiple accounting subsystems
+- extensibility for use by future accounting patches
+
+Terminology
+-----------
+
+"pid", "tid" and "task" are used interchangeably and refer to the standard
+Linux task defined by struct task_struct.  per-pid stats are the same as
+per-task stats.
+
+"tgid", "process" and "thread group" are used interchangeably and refer to the
+tasks that share an mm_struct i.e. the traditional Unix process. Despite the
+use of tgid, there is no special treatment for the task that is thread group
+leader - a process is deemed alive as long as it has any task belonging to it.
+
+Usage
+-----
+
+To get statistics during task's lifetime, userspace opens a unicast netlink
+socket (NETLINK_GENERIC family) and sends commands specifying a pid or a tgid.
+The response contains statistics for a task (if pid is specified) or the sum of
+statistics for all tasks of the process (if tgid is specified).
+
+To obtain statistics for tasks which are exiting, userspace opens a multicast
+netlink socket. Each time a task exits, two records are sent by the kernel to
+each listener on the multicast socket. The first the per-pid task's statistics
+and the second is the sum for all tasks of the process to which the task
+belongs (the task does not need to be the thread group leader). The need for
+per-tgid stats to be sent for each exiting task is explained in the per-tgid
+stats section below.
+
+
+Interface
+---------
+
+The user-kernel interface is encapsulated in include/linux/taskstats.h
+
+To avoid this documentation becoming obsolete as the interface evolves, only
+an outline of the current version is given. taskstats.h always overrides the
+description here.
+
+struct taskstats is the common accounting structure for both per-pid and
+per-tgid data. It is versioned and can be extended by each accounting subsystem
+that is added to the kernel. The fields and their semantics are defined in the
+taskstats.h file.
+
+The data exchanged between user and kernel space is a netlink message belonging
+to the NETLINK_GENERIC family and using the netlink attributes interface.
+The messages are in the format
+
+    +----------+- - -+-------------+-------------------+
+    | nlmsghdr | Pad |  genlmsghdr | taskstats payload |
+    +----------+- - -+-------------+-------------------+
+
+
+The taskstats payload is one of the following three kinds:
+
+1. Commands: Sent from user to kernel. The payload is one attribute, of type
+TASKSTATS_CMD_ATTR_PID/TGID, containing a u32 pid or tgid in the attribute
+payload. The pid/tgid denotes the task/process for which userspace wants
+statistics.
+
+2. Response for a command: sent from the kernel in response to a userspace
+command. The payload is a series of three attributes of type:
+
+a) TASKSTATS_TYPE_AGGR_PID/TGID : attribute containing no payload but indicates
+a pid/tgid will be followed by some stats.
+
+b) TASKSTATS_TYPE_PID/TGID: attribute whose payload is the pid/tgid whose stats
+is being returned.
+
+c) TASKSTATS_TYPE_STATS: attribute with a struct taskstsats as payload. The
+same structure is used for both per-pid and per-tgid stats.
+
+3. New message sent by kernel whenever a task exits. The payload consists of a
+   series of attributes of the following type:
+
+a) TASKSTATS_TYPE_AGGR_PID: indicates next two attributes will be pid+stats
+b) TASKSTATS_TYPE_PID: contains exiting task's pid
+c) TASKSTATS_TYPE_STATS: contains the exiting task's per-pid stats
+d) TASKSTATS_TYPE_AGGR_TGID: indicates next two attributes will be tgid+stats
+e) TASKSTATS_TYPE_TGID: contains tgid of process to which task belongs
+f) TASKSTATS_TYPE_STATS: contains the per-tgid stats for exiting task's process
+
+
+per-tgid stats
+--------------
+
+Taskstats provides per-process stats, in addition to per-task stats, since
+resource management is often done at a process granularity and aggregating task
+stats in userspace alone is inefficient and potentially inaccurate (due to lack
+of atomicity).
+
+However, maintaining per-process, in addition to per-task stats, within the
+kernel has space and time overheads. Hence the taskstats implementation
+dynamically sums up the per-task stats for each task belonging to a process
+whenever per-process stats are needed.
+
+Not maintaining per-tgid stats creates a problem when userspace is interested
+in getting these stats when the process dies i.e. the last thread of
+a process exits. It isn't possible to simply return some aggregated per-process
+statistic from the kernel.
+
+The approach taken by taskstats is to return the per-tgid stats *each* time
+a task exits, in addition to the per-pid stats for that task. Userspace can
+maintain task<->process mappings and use them to maintain the per-process stats
+in userspace, updating the aggregate appropriately as the tasks of a process
+exit.
+
+Extending taskstats
+-------------------
+
+There are two ways to extend the taskstats interface to export more
+per-task/process stats as patches to collect them get added to the kernel
+in future:
+
+1. Adding more fields to the end of the existing struct taskstats. Backward
+   compatibility is ensured by the version number within the
+   structure. Userspace will use only the fields of the struct that correspond
+   to the version its using.
+
+2. Defining separate statistic structs and using the netlink attributes
+   interface to return them. Since userspace processes each netlink attribute
+   independently, it can always ignore attributes whose type it does not
+   understand (because it is using an older version of the interface).
+
+
+Choosing between 1. and 2. is a matter of trading off flexibility and
+overhead. If only a few fields need to be added, then 1. is the preferable
+path since the kernel and userspace don't need to incur the overhead of
+processing new netlink attributes. But if the new fields expand the existing
+struct too much, requiring disparate userspace accounting utilities to
+unnecessarily receive large structures whose fields are of no interest, then
+extending the attributes structure would be worthwhile.
+
+----
diff --git a/include/linux/taskstats.h b/include/linux/taskstats.h
new file mode 100644
index 000000000000..51f62759bea9
--- /dev/null
+++ b/include/linux/taskstats.h
@@ -0,0 +1,84 @@
+/* taskstats.h - exporting per-task statistics
+ *
+ * Copyright (C) Shailabh Nagar, IBM Corp. 2006
+ *           (C) Balbir Singh,   IBM Corp. 2006
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of version 2.1 of the GNU Lesser General Public License
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ */
+
+#ifndef _LINUX_TASKSTATS_H
+#define _LINUX_TASKSTATS_H
+
+/* Format for per-task data returned to userland when
+ *      - a task exits
+ *      - listener requests stats for a task
+ *
+ * The struct is versioned. Newer versions should only add fields to
+ * the bottom of the struct to maintain backward compatibility.
+ *
+ *
+ * To add new fields
+ *      a) bump up TASKSTATS_VERSION
+ *      b) add comment indicating new version number at end of struct
+ *      c) add new fields after version comment; maintain 64-bit alignment
+ */
+
+#define TASKSTATS_VERSION       1
+
+struct taskstats {
+
+        /* Version 1 */
+        __u64   version;
+};
+
+
+#define TASKSTATS_LISTEN_GROUP  0x1
+
+/*
+ * Commands sent from userspace
+ * Not versioned. New commands should only be inserted at the enum's end
+ * prior to __TASKSTATS_CMD_MAX
+ */
+
+enum {
+        TASKSTATS_CMD_UNSPEC = 0,       /* Reserved */
+        TASKSTATS_CMD_GET,              /* user->kernel request/get-response */
+        TASKSTATS_CMD_NEW,              /* kernel->user event */
+        __TASKSTATS_CMD_MAX,
+};
+
+#define TASKSTATS_CMD_MAX (__TASKSTATS_CMD_MAX - 1)
+
+enum {
+        TASKSTATS_TYPE_UNSPEC = 0,      /* Reserved */
+        TASKSTATS_TYPE_PID,             /* Process id */
+        TASKSTATS_TYPE_TGID,            /* Thread group id */
+        TASKSTATS_TYPE_STATS,           /* taskstats structure */
+        TASKSTATS_TYPE_AGGR_PID,        /* contains pid + stats */
+        TASKSTATS_TYPE_AGGR_TGID,       /* contains tgid + stats */
+        __TASKSTATS_TYPE_MAX,
+};
+
+#define TASKSTATS_TYPE_MAX (__TASKSTATS_TYPE_MAX - 1)
+
+enum {
+        TASKSTATS_CMD_ATTR_UNSPEC = 0,
+        TASKSTATS_CMD_ATTR_PID,
+        TASKSTATS_CMD_ATTR_TGID,
+        __TASKSTATS_CMD_ATTR_MAX,
+};
+
+#define TASKSTATS_CMD_ATTR_MAX (__TASKSTATS_CMD_ATTR_MAX - 1)
+
+/* NETLINK_GENERIC related info */
+
+#define TASKSTATS_GENL_NAME     "TASKSTATS"
+#define TASKSTATS_GENL_VERSION  0x1
+
+#endif /* _LINUX_TASKSTATS_H */
diff --git a/include/linux/taskstats_kern.h b/include/linux/taskstats_kern.h
new file mode 100644
index 000000000000..bd0ecb969c26
--- /dev/null
+++ b/include/linux/taskstats_kern.h
@@ -0,0 +1,57 @@
+/* taskstats_kern.h - kernel header for per-task statistics interface
+ *
+ * Copyright (C) Shailabh Nagar, IBM Corp. 2006
+ *           (C) Balbir Singh,   IBM Corp. 2006
+ */
+
+#ifndef _LINUX_TASKSTATS_KERN_H
+#define _LINUX_TASKSTATS_KERN_H
+
+#include <linux/taskstats.h>
+#include <linux/sched.h>
+
+enum {
+        TASKSTATS_MSG_UNICAST,          /* send data only to requester */
+        TASKSTATS_MSG_MULTICAST,        /* send data to a group */
+};
+
+#ifdef CONFIG_TASKSTATS
+extern kmem_cache_t *taskstats_cache;
+
+static inline void taskstats_exit_alloc(struct taskstats **ptidstats,
+                                        struct taskstats **ptgidstats)
+{
+        *ptidstats = kmem_cache_zalloc(taskstats_cache, SLAB_KERNEL);
+        *ptgidstats = kmem_cache_zalloc(taskstats_cache, SLAB_KERNEL);
+}
+
+static inline void taskstats_exit_free(struct taskstats *tidstats,
+                                        struct taskstats *tgidstats)
+{
+        if (tidstats)
+                kmem_cache_free(taskstats_cache, tidstats);
+        if (tgidstats)
+                kmem_cache_free(taskstats_cache, tgidstats);
+}
+
+extern void taskstats_exit_send(struct task_struct *, struct taskstats *,
+                                struct taskstats *);
+extern void taskstats_init_early(void);
+
+#else
+static inline void taskstats_exit_alloc(struct taskstats **ptidstats,
+                                        struct taskstats **ptgidstats)
+{}
+static inline void taskstats_exit_free(struct taskstats *ptidstats,
+                                        struct taskstats *ptgidstats)
+{}
+static inline void taskstats_exit_send(struct task_struct *tsk,
+                                        struct taskstats *tidstats,
+                                        struct taskstats *tgidstats)
+{}
+static inline void taskstats_init_early(void)
+{}
+#endif /* CONFIG_TASKSTATS */
+
+#endif
+
diff --git a/init/Kconfig b/init/Kconfig
index 90498a3e53da..56a7093b4e4c 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -158,6 +158,19 @@ config BSD_PROCESS_ACCT_V3
           for processing it. A preliminary version of these tools is available
           at <http://www.physik3.uni-rostock.de/tim/kernel/utils/acct/>.
 
+config TASKSTATS
+        bool "Export task/process statistics through netlink (EXPERIMENTAL)"
+        depends on NET
+        default n
+        help
+          Export selected statistics for tasks/processes through the
+          generic netlink interface. Unlike BSD process accounting, the
+          statistics are available during the lifetime of tasks/processes as
+          responses to commands. Like BSD accounting, they are sent to user
+          space on task exit.
+
+          Say N if unsure.
+
 config TASK_DELAY_ACCT
         bool "Enable per-task delay accounting (EXPERIMENTAL)"
         help
diff --git a/init/main.c b/init/main.c
index 9e8e8c152142..8651a720a092 100644
--- a/init/main.c
+++ b/init/main.c
@@ -41,6 +41,7 @@
 #include <linux/cpu.h>
 #include <linux/cpuset.h>
 #include <linux/efi.h>
+#include <linux/taskstats_kern.h>
 #include <linux/delayacct.h>
 #include <linux/unistd.h>
 #include <linux/rmap.h>
@@ -575,6 +576,7 @@ asmlinkage void __init start_kernel(void)
         proc_root_init();
 #endif
         cpuset_init();
+        taskstats_init_early();
         delayacct_init();
 
         check_bugs();
diff --git a/kernel/Makefile b/kernel/Makefile
index 87bb34cc8938..d62ec66c1af2 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -49,6 +49,7 @@ obj-$(CONFIG_SECCOMP) += seccomp.o
 obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
 obj-$(CONFIG_RELAY) += relay.o
 obj-$(CONFIG_TASK_DELAY_ACCT) += delayacct.o
+obj-$(CONFIG_TASKSTATS) += taskstats.o
 
 ifneq ($(CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER),y)
 # According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
diff --git a/kernel/exit.c b/kernel/exit.c
index 3c2cf91defa7..9852ed8c2988 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -25,6 +25,7 @@
 #include <linux/mount.h>
 #include <linux/proc_fs.h>
 #include <linux/mempolicy.h>
+#include <linux/taskstats_kern.h>
 #include <linux/delayacct.h>
 #include <linux/cpuset.h>
 #include <linux/syscalls.h>
@@ -844,6 +845,7 @@ static void exit_notify(struct task_struct *tsk)
 fastcall NORET_TYPE void do_exit(long code)
 {
         struct task_struct *tsk = current;
+        struct taskstats *tidstats, *tgidstats;
         int group_dead;
 
         profile_task_exit(tsk);
@@ -882,6 +884,8 @@ fastcall NORET_TYPE void do_exit(long code)
                                 current->comm, current->pid,
                                 preempt_count());
 
+        taskstats_exit_alloc(&tidstats, &tgidstats);
+
         acct_update_integrals(tsk);
         if (tsk->mm) {
                 update_hiwater_rss(tsk->mm);
@@ -901,7 +905,10 @@ fastcall NORET_TYPE void do_exit(long code)
 #endif
         if (unlikely(tsk->audit_context))
                 audit_free(tsk);
+        taskstats_exit_send(tsk, tidstats, tgidstats);
+        taskstats_exit_free(tidstats, tgidstats);
         delayacct_tsk_exit(tsk);
+
         exit_mm(tsk);
 
         if (group_dead)
diff --git a/kernel/taskstats.c b/kernel/taskstats.c
new file mode 100644
index 000000000000..82ec9137d908
--- /dev/null
+++ b/kernel/taskstats.c
@@ -0,0 +1,336 @@
+/*
+ * taskstats.c - Export per-task statistics to userland
+ *
+ * Copyright (C) Shailabh Nagar, IBM Corp. 2006
+ *           (C) Balbir Singh,   IBM Corp. 2006
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/taskstats_kern.h>
+#include <net/genetlink.h>
+#include <asm/atomic.h>
+
+static DEFINE_PER_CPU(__u32, taskstats_seqnum) = { 0 };
+static int family_registered;
+kmem_cache_t *taskstats_cache;
+static DEFINE_MUTEX(taskstats_exit_mutex);
+
+static struct genl_family family = {
+        .id             = GENL_ID_GENERATE,
+        .name           = TASKSTATS_GENL_NAME,
+        .version        = TASKSTATS_GENL_VERSION,
+        .maxattr        = TASKSTATS_CMD_ATTR_MAX,
+};
+
+static struct nla_policy taskstats_cmd_get_policy[TASKSTATS_CMD_ATTR_MAX+1]
+__read_mostly = {
+        [TASKSTATS_CMD_ATTR_PID]  = { .type = NLA_U32 },
+        [TASKSTATS_CMD_ATTR_TGID] = { .type = NLA_U32 },
+};
+
+
+static int prepare_reply(struct genl_info *info, u8 cmd, struct sk_buff **skbp,
+                        void **replyp, size_t size)
+{
+        struct sk_buff *skb;
+        void *reply;
+
+        /*
+         * If new attributes are added, please revisit this allocation
+         */
+        skb = nlmsg_new(size);
+        if (!skb)
+                return -ENOMEM;
+
+        if (!info) {
+                int seq = get_cpu_var(taskstats_seqnum)++;
+                put_cpu_var(taskstats_seqnum);
+
+                reply = genlmsg_put(skb, 0, seq,
+                                family.id, 0, 0,
+                                cmd, family.version);
+        } else
+                reply = genlmsg_put(skb, info->snd_pid, info->snd_seq,
+                                family.id, 0, 0,
+                                cmd, family.version);
+        if (reply == NULL) {
+                nlmsg_free(skb);
+                return -EINVAL;
+        }
+
+        *skbp = skb;
+        *replyp = reply;
+        return 0;
+}
+
+static int send_reply(struct sk_buff *skb, pid_t pid, int event)
+{
+        struct genlmsghdr *genlhdr = nlmsg_data((struct nlmsghdr *)skb->data);
+        void *reply;
+        int rc;
+
+        reply = genlmsg_data(genlhdr);
+
+        rc = genlmsg_end(skb, reply);
+        if (rc < 0) {
+                nlmsg_free(skb);
+                return rc;
+        }
+
+        if (event == TASKSTATS_MSG_MULTICAST)
+                return genlmsg_multicast(skb, pid, TASKSTATS_LISTEN_GROUP);
+        return genlmsg_unicast(skb, pid);
+}
+
+static int fill_pid(pid_t pid, struct task_struct *pidtsk,
+                struct taskstats *stats)
+{
+        int rc;
+        struct task_struct *tsk = pidtsk;
+
+        if (!pidtsk) {
+                read_lock(&tasklist_lock);
+                tsk = find_task_by_pid(pid);
+                if (!tsk) {
+                        read_unlock(&tasklist_lock);
+                        return -ESRCH;
+                }
+                get_task_struct(tsk);
+                read_unlock(&tasklist_lock);
+        } else
+                get_task_struct(tsk);
+
+        /*
+         * Each accounting subsystem adds calls to its functions to
+         * fill in relevant parts of struct taskstsats as follows
+         *
+         *      rc = per-task-foo(stats, tsk);
+         *      if (rc)
+         *              goto err;
+         */
+
+err:
+        put_task_struct(tsk);
+        return rc;
+
+}
+
+static int fill_tgid(pid_t tgid, struct task_struct *tgidtsk,
+                struct taskstats *stats)
+{
+        int rc;
+        struct task_struct *tsk, *first;
+
+        first = tgidtsk;
+        read_lock(&tasklist_lock);
+        if (!first) {
+                first = find_task_by_pid(tgid);
+                if (!first) {
+                        read_unlock(&tasklist_lock);
+                        return -ESRCH;
+                }
+        }
+        tsk = first;
+        do {
+                /*
+                 * Each accounting subsystem adds calls its functions to
+                 * fill in relevant parts of struct taskstsats as follows
+                 *
+                 *      rc = per-task-foo(stats, tsk);
+                 *      if (rc)
+                 *              break;
+                 */
+
+        } while_each_thread(first, tsk);
+        read_unlock(&tasklist_lock);
+
+        /*
+         * Accounting subsytems can also add calls here if they don't
+         * wish to aggregate statistics for per-tgid stats
+         */
+
+        return rc;
+}
+
+static int taskstats_send_stats(struct sk_buff *skb, struct genl_info *info)
+{
+        int rc = 0;
+        struct sk_buff *rep_skb;
+        struct taskstats stats;
+        void *reply;
+        size_t size;
+        struct nlattr *na;
+
+        /*
+         * Size includes space for nested attributes
+         */
+        size = nla_total_size(sizeof(u32)) +
+                nla_total_size(sizeof(struct taskstats)) + nla_total_size(0);
+
+        memset(&stats, 0, sizeof(stats));
+        rc = prepare_reply(info, TASKSTATS_CMD_NEW, &rep_skb, &reply, size);
+        if (rc < 0)
+                return rc;
+
+        if (info->attrs[TASKSTATS_CMD_ATTR_PID]) {
+                u32 pid = nla_get_u32(info->attrs[TASKSTATS_CMD_ATTR_PID]);
+                rc = fill_pid(pid, NULL, &stats);
+                if (rc < 0)
+                        goto err;
+
+                na = nla_nest_start(rep_skb, TASKSTATS_TYPE_AGGR_PID);
+                NLA_PUT_U32(rep_skb, TASKSTATS_TYPE_PID, pid);
+                NLA_PUT_TYPE(rep_skb, struct taskstats, TASKSTATS_TYPE_STATS,
+                                stats);
+        } else if (info->attrs[TASKSTATS_CMD_ATTR_TGID]) {
+                u32 tgid = nla_get_u32(info->attrs[TASKSTATS_CMD_ATTR_TGID]);
+                rc = fill_tgid(tgid, NULL, &stats);
+                if (rc < 0)
+                        goto err;
+
+                na = nla_nest_start(rep_skb, TASKSTATS_TYPE_AGGR_TGID);
+                NLA_PUT_U32(rep_skb, TASKSTATS_TYPE_TGID, tgid);
+                NLA_PUT_TYPE(rep_skb, struct taskstats, TASKSTATS_TYPE_STATS,
+                                stats);
+        } else {
+                rc = -EINVAL;
+                goto err;
+        }
+
+        nla_nest_end(rep_skb, na);
+
+        return send_reply(rep_skb, info->snd_pid, TASKSTATS_MSG_UNICAST);
+
+nla_put_failure:
+        return genlmsg_cancel(rep_skb, reply);
+err:
+        nlmsg_free(rep_skb);
+        return rc;
+}
+
+/* Send pid data out on exit */
+void taskstats_exit_send(struct task_struct *tsk, struct taskstats *tidstats,
+                        struct taskstats *tgidstats)
+{
+        int rc;
+        struct sk_buff *rep_skb;
+        void *reply;
+        size_t size;
+        int is_thread_group;
+        struct nlattr *na;
+
+        if (!family_registered || !tidstats)
+                return;
+
+        mutex_lock(&taskstats_exit_mutex);
+
+        is_thread_group = !thread_group_empty(tsk);
+        rc = 0;
+
+        /*
+         * Size includes space for nested attributes
+         */
+        size = nla_total_size(sizeof(u32)) +
+                nla_total_size(sizeof(struct taskstats)) + nla_total_size(0);
+
+        if (is_thread_group)
+                size = 2 * size;        /* PID + STATS + TGID + STATS */
+
+        rc = prepare_reply(NULL, TASKSTATS_CMD_NEW, &rep_skb, &reply, size);
+        if (rc < 0)
+                goto ret;
+
+        rc = fill_pid(tsk->pid, tsk, tidstats);
+        if (rc < 0)
+                goto err_skb;
+
+        na = nla_nest_start(rep_skb, TASKSTATS_TYPE_AGGR_PID);
+        NLA_PUT_U32(rep_skb, TASKSTATS_TYPE_PID, (u32)tsk->pid);
+        NLA_PUT_TYPE(rep_skb, struct taskstats, TASKSTATS_TYPE_STATS,
+                        *tidstats);
+        nla_nest_end(rep_skb, na);
+
+        if (!is_thread_group || !tgidstats) {
+                send_reply(rep_skb, 0, TASKSTATS_MSG_MULTICAST);
+                goto ret;
+        }
+
+        rc = fill_tgid(tsk->pid, tsk, tgidstats);
+        /*
+         * If fill_tgid() failed then one probable reason could be that the
+         * thread group leader has exited. fill_tgid() will fail, send out
+         * the pid statistics collected earlier.
+         */
+        if (rc < 0) {
+                send_reply(rep_skb, 0, TASKSTATS_MSG_MULTICAST);
+                goto ret;
+        }
+
+        na = nla_nest_start(rep_skb, TASKSTATS_TYPE_AGGR_TGID);
+        NLA_PUT_U32(rep_skb, TASKSTATS_TYPE_TGID, (u32)tsk->tgid);
+        NLA_PUT_TYPE(rep_skb, struct taskstats, TASKSTATS_TYPE_STATS,
+                        *tgidstats);
+        nla_nest_end(rep_skb, na);
+
+        send_reply(rep_skb, 0, TASKSTATS_MSG_MULTICAST);
+        goto ret;
+
+nla_put_failure:
+        genlmsg_cancel(rep_skb, reply);
+        goto ret;
+err_skb:
+        nlmsg_free(rep_skb);
+ret:
+        mutex_unlock(&taskstats_exit_mutex);
+        return;
+}
+
+static struct genl_ops taskstats_ops = {
+        .cmd            = TASKSTATS_CMD_GET,
+        .doit           = taskstats_send_stats,
+        .policy         = taskstats_cmd_get_policy,
+};
+
+/* Needed early in initialization */
+void __init taskstats_init_early(void)
+{
+        taskstats_cache = kmem_cache_create("taskstats_cache",
+                                                sizeof(struct taskstats),
+                                                0, SLAB_PANIC, NULL, NULL);
+}
+
+static int __init taskstats_init(void)
+{
+        int rc;
+
+        rc = genl_register_family(&family);
+        if (rc)
+                return rc;
+
+        rc = genl_register_ops(&family, &taskstats_ops);
+        if (rc < 0)
+                goto err;
+
+        family_registered = 1;
+        return 0;
+err:
+        genl_unregister_family(&family);
+        return rc;
+}
+
+/*
+ * late initcall ensures initialization of statistics collection
+ * mechanisms precedes initialization of the taskstats interface
+ */
+late_initcall(taskstats_init);