TASKSTATS_CMD_ATTR_TGID used to return only the delay accounting stats, not
the basic and extended accounting. With this patch,
TASKSTATS_CMD_ATTR_TGID also aggregates the accounting info for all threads
of a thread group.

TASKSTATS_CMD_ATTR_PID output should be unchanged
TASKSTATS_CMD_ATTR_TGID output should have all fields set, unlike before the
patch where most of the fiels were set to 0.

To this aim, two functions were introduced: fill_threadgroup_stats() and
add_tsk_stats(). These functions are responsible for aggregating the
subsystem specific accounting information. Taskstats requesters (fill_pid(),
fill_tgid() and fill_tgid_exit()) should only call add_tsk_stats() and
fill_threadgroup_stats() to get the stats.

Signed-off-by: Guillaume Chazarain
Cc: Balbir Singh
Cc: Jay Lan
Cc: Jonathan Lim
Cc: Oleg Nesterov
---

Documentation/accounting/getdelays.c | 2 -
include/linux/tsacct_kern.h | 12 +++-
kernel/taskstats.c | 107 +++++++++++++++++++++++-----------
kernel/tsacct.c | 20 +-----
4 files changed, 85 insertions(+), 56 deletions(-)


diff --git a/Documentation/accounting/getdelays.c b/Documentation/accounting/getdelays.c
index cbee3a2..78773c0 100644
--- a/Documentation/accounting/getdelays.c
+++ b/Documentation/accounting/getdelays.c
@@ -76,7 +76,7 @@ static void usage(void)
fprintf(stderr, "getdelays [-dilv] [-w logfile] [-r bufsize] "
"[-m cpumask] [-t tgid] [-p pid]\n");
fprintf(stderr, " -d: print delayacct stats\n");
- fprintf(stderr, " -i: print IO accounting (works only with -p)\n");
+ fprintf(stderr, " -i: print IO accounting\n");
fprintf(stderr, " -l: listen forever\n");
fprintf(stderr, " -v: debug on\n");
}
diff --git a/include/linux/tsacct_kern.h b/include/linux/tsacct_kern.h
index 7e50ac7..1568a3d 100644
--- a/include/linux/tsacct_kern.h
+++ b/include/linux/tsacct_kern.h
@@ -10,19 +10,25 @@
#include

#ifdef CONFIG_TASKSTATS
-extern void bacct_add_tsk(struct taskstats *stats, struct task_struct *tsk);
+void bacct_add_tsk(struct taskstats *stats, struct task_struct *task);
+void bacct_fill_threadgroup(struct taskstats *stats, struct task_struct *task);
#else
-static inline void bacct_add_tsk(struct taskstats *stats, struct task_struct *tsk)
+static inline void bacct_add_tsk(struct taskstats *stats, struct task_struct *task)
+{}
+static inline void bacct_fill_threadgroup(struct taskstats *stats, struct task_struct *task)
{}
#endif /* CONFIG_TASKSTATS */

#ifdef CONFIG_TASK_XACCT
-extern void xacct_add_tsk(struct taskstats *stats, struct task_struct *p);
+void xacct_add_tsk(struct taskstats *stats, struct task_struct *p);
+void xacct_fill_threadgroup(struct taskstats *stats, struct task_struct *task);
extern void acct_update_integrals(struct task_struct *tsk);
extern void acct_clear_integrals(struct task_struct *tsk);
#else
static inline void xacct_add_tsk(struct taskstats *stats, struct task_struct *p)
{}
+static inline void xacct_fill_threadgroup(struct taskstats *stats, struct task_struct *task)
+{}
static inline void acct_update_integrals(struct task_struct *tsk)
{}
static inline void acct_clear_integrals(struct task_struct *tsk)
diff --git a/kernel/taskstats.c b/kernel/taskstats.c
index a42b6c0..972bbfa 100644
--- a/kernel/taskstats.c
+++ b/kernel/taskstats.c
@@ -168,6 +168,63 @@ static void send_cpu_listeners(struct sk_buff *skb,
up_write(&listeners->sem);
}

+/**
+ * add_tsk_stats - combine some thread specific stats in a taskstats
+ * @stats: the taskstats to write into
+ * @task: the thread to combine
+ *
+ * There are two types of taskstats fields when considering a thread group:
+ * - those that can be aggregated from each thread in the group (like CPU
+ * times),
+ * - those that cannot be aggregated (like UID) or are identical (like
+ * memory usage), so are taken from the group leader.
+ * XXX_add_tsk() methods deal with the first type while XXX_fill_threadgroup()
+ * with the second one.
+ */
+static void add_tsk_stats(struct taskstats *stats, struct task_struct *task)
+{
+ /*
+ * Each accounting subsystem adds calls to its functions to combine
+ * relevant parts of struct taskstsats for a single pid as follows:
+ *
+ * per-task-foo-add_tsk_stats(stats, task);
+ */
+
+ /* fill in delay acct fields */
+ delayacct_add_tsk(stats, task);
+
+ /* fill in basic acct fields */
+ bacct_add_tsk(stats, task);
+
+ /* fill in extended acct fields */
+ xacct_add_tsk(stats, task);
+}
+
+/**
+ * fill_threadgroup_stats - initialize some common stats for the thread group
+ * @stats: the taskstats to write into
+ * @task: the thread representing the whole group
+ *
+ * Will be called on the thread group leader if requesting stats for the whole
+ * thread group.
+ */
+static void fill_threadgroup_stats(struct taskstats *stats,
+ struct task_struct *task)
+{
+ /*
+ * Each accounting subsystem adds calls to its functions to initialize
+ * relevant parts of struct taskstsats for a single tgid as follows:
+ *
+ * per-task-foo-fill_threadgroup(stats, task);
+ */
+
+ /* fill in basic acct fields */
+ bacct_fill_threadgroup(stats, task);
+
+ /* fill in extended acct fields */
+ xacct_fill_threadgroup(stats, task);
+}
+
static int fill_pid(pid_t pid, struct task_struct *tsk, struct taskstats *stats)
{
int rc = 0;
@@ -184,23 +241,11 @@ static int fill_pid(pid_t pid, struct task_struct *tsk, struct taskstats *stats)
get_task_struct(tsk);

memset(stats, 0, sizeof(*stats));
- /*
- * Each accounting subsystem adds calls to its functions to
- * fill in relevant parts of struct taskstsats as follows
- *
- * per-task-foo(stats, tsk);
- */
-
- delayacct_add_tsk(stats, tsk);
-
- /* fill in basic acct fields */
stats->version = TASKSTATS_VERSION;
stats->nvcsw = tsk->nvcsw;
stats->nivcsw = tsk->nivcsw;
- bacct_add_tsk(stats, tsk);
-
- /* fill in extended acct fields */
- xacct_add_tsk(stats, tsk);
+ add_tsk_stats(stats, tsk);
+ fill_threadgroup_stats(stats, tsk);

/* Define err: label here if needed */
put_task_struct(tsk);
@@ -236,27 +281,20 @@ static int fill_tgid(pid_t tgid, struct task_struct *first,
if (tsk->exit_state)
continue;
/*
- * Accounting subsystem can call its functions here to
- * fill in relevant parts of struct taskstsats as follows
- *
- * per-task-foo(stats, tsk);
+ * This check is racy as a thread could exit just right
+ * now and have its statistics accounted twice.
*/
- delayacct_add_tsk(stats, tsk);
-
+ add_tsk_stats(stats, tsk);
stats->nvcsw += tsk->nvcsw;
stats->nivcsw += tsk->nivcsw;
} while_each_thread(first, tsk);

+ fill_threadgroup_stats(stats, first->group_leader);
unlock_task_sighand(first, &flags);
rc = 0;
out:
rcu_read_unlock();
-
stats->version = TASKSTATS_VERSION;
- /*
- * Accounting subsytems can also add calls here to modify
- * fields of taskstats.
- */
return rc;
}

@@ -266,19 +304,14 @@ static void fill_tgid_exit(struct task_struct *tsk)
unsigned long flags;

spin_lock_irqsave(&tsk->sighand->siglock, flags);
- if (!tsk->signal->stats)
- goto ret;

/*
- * Each accounting subsystem calls its functions here to
- * accumalate its per-task stats for tsk, into the per-tgid structure
- *
- * per-task-foo(tsk->signal->stats, tsk);
+ * The fill_threadgroup_stats() part of the statistics will be added by
+ * the stats requester, i.e. fill_tgid() or taskstats_exit()
*/
- delayacct_add_tsk(tsk->signal->stats, tsk);
-ret:
+ add_tsk_stats(tsk->signal->stats, tsk);
+
spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
- return;
}

static int add_del_listener(pid_t pid, cpumask_t *maskp, int isadd)
@@ -507,7 +540,13 @@ void taskstats_exit(struct task_struct *tsk, int group_dead)
if (!stats)
goto err;

+ /*
+ * Race here: the last thread may have not finished its
+ * fill_tgid_exit(), leaving an incomplete tsk->signal->stats
+ */
+
memcpy(stats, tsk->signal->stats, sizeof(*stats));
+ fill_threadgroup_stats(stats, tsk->group_leader);

send:
send_cpu_listeners(rep_skb, listeners);
diff --git a/kernel/tsacct.c b/kernel/tsacct.c
index e8c25d2..4caea73 100644
--- a/kernel/tsacct.c
+++ b/kernel/tsacct.c
@@ -40,13 +40,6 @@ static void fill_wall_times(struct taskstats *stats, struct task_struct *tsk)
stats->ac_btime = get_seconds() - ts.tv_sec;
}

-/*
- * Later on, XXX_add_tsk() will need to be called after XXX_fill_threadgroup(),
- * so put the functions in this order
- */
-static void bacct_fill_threadgroup(struct taskstats *stats,
- struct task_struct *tsk);
-
void bacct_add_tsk(struct taskstats *stats, struct task_struct *tsk)
{
if (tsk->flags & PF_SUPERPRIV)
@@ -64,12 +57,9 @@ void bacct_add_tsk(struct taskstats *stats, struct task_struct *tsk)
cputime_to_msecs(tsk->stimescaled) * USEC_PER_MSEC;
stats->ac_minflt += tsk->min_flt;
stats->ac_majflt += tsk->maj_flt;
-
- bacct_fill_threadgroup(stats, tsk);
}

-static void bacct_fill_threadgroup(struct taskstats *stats,
- struct task_struct *tsk)
+void bacct_fill_threadgroup(struct taskstats *stats, struct task_struct *tsk)
{
fill_wall_times(stats, tsk);

@@ -102,9 +92,6 @@ static void bacct_fill_threadgroup(struct taskstats *stats,
* fill in extended accounting fields
*/

-static void xacct_fill_threadgroup(struct taskstats *stats,
- struct task_struct *tsk);
-
void xacct_add_tsk(struct taskstats *stats, struct task_struct *tsk)
{
/* convert pages-jiffies to Mbyte-usec */
@@ -120,12 +107,9 @@ void xacct_add_tsk(struct taskstats *stats, struct task_struct *tsk)
stats->write_bytes += tsk->ioac.write_bytes;
stats->cancelled_write_bytes += tsk->ioac.cancelled_write_bytes;
#endif
-
- xacct_fill_threadgroup(stats, tsk);
}

-static void xacct_fill_threadgroup(struct taskstats *stats,
- struct task_struct *tsk)
+void xacct_fill_threadgroup(struct taskstats *stats, struct task_struct *tsk)
{
struct mm_struct *mm;

-
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