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Subject[PATCH] cgroup: add tracepoints for basic operations
From 471f89b317a21a78dacaee85957984b9f11e79e4 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Tue, 9 Aug 2016 01:11:13 -0400

Debugging what goes wrong with cgroup setup can get hairy. Add
tracepoints for cgroup hierarchy mount, cgroup creation/destruction
and task migration operations for better visibility.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
This patchset is on top of

v4.8-rc1 29b4817d4018df78086157ea3a55c1d9424a7cfc
+ [PATCHSET] kernfs, cgroup: make kernfs_path*() and cgroup_path*() behave in strlcpy() style
http://lkml.kernel.org/r/1470720204-4605-1-git-send-email-tj@kernel.org

and also available in the following git branch.

git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git review-tracepoints

Thanks.

include/trace/events/cgroup.h | 163 ++++++++++++++++++++++++++++++++++++++++++
kernel/cgroup.c | 25 +++++++
2 files changed, 188 insertions(+)
create mode 100644 include/trace/events/cgroup.h

diff --git a/include/trace/events/cgroup.h b/include/trace/events/cgroup.h
new file mode 100644
index 0000000..ab68640
--- /dev/null
+++ b/include/trace/events/cgroup.h
@@ -0,0 +1,163 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM cgroup
+
+#if !defined(_TRACE_CGROUP_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_CGROUP_H
+
+#include <linux/cgroup.h>
+#include <linux/tracepoint.h>
+
+DECLARE_EVENT_CLASS(cgroup_root,
+
+ TP_PROTO(struct cgroup_root *root),
+
+ TP_ARGS(root),
+
+ TP_STRUCT__entry(
+ __field( int, root )
+ __field( u16, ss_mask )
+ __string( name, root->name )
+ ),
+
+ TP_fast_assign(
+ __entry->root = root->hierarchy_id;
+ __entry->ss_mask = root->subsys_mask;
+ __assign_str(name, root->name);
+ ),
+
+ TP_printk("root=%d ss_mask=%#x name=%s",
+ __entry->root, __entry->ss_mask, __get_str(name))
+);
+
+DEFINE_EVENT(cgroup_root, cgroup_setup_root,
+
+ TP_PROTO(struct cgroup_root *root),
+
+ TP_ARGS(root)
+);
+
+DEFINE_EVENT(cgroup_root, cgroup_destroy_root,
+
+ TP_PROTO(struct cgroup_root *root),
+
+ TP_ARGS(root)
+);
+
+DEFINE_EVENT(cgroup_root, cgroup_remount,
+
+ TP_PROTO(struct cgroup_root *root),
+
+ TP_ARGS(root)
+);
+
+DECLARE_EVENT_CLASS(cgroup,
+
+ TP_PROTO(struct cgroup *cgrp),
+
+ TP_ARGS(cgrp),
+
+ TP_STRUCT__entry(
+ __field( int, root )
+ __field( int, id )
+ __field( int, level )
+ __dynamic_array(char, path,
+ cgrp->kn ? cgroup_path(cgrp, NULL, 0) + 1
+ : strlen("(null)"))
+ ),
+
+ TP_fast_assign(
+ __entry->root = cgrp->root->hierarchy_id;
+ __entry->id = cgrp->id;
+ __entry->level = cgrp->level;
+ if (cgrp->kn)
+ cgroup_path(cgrp, __get_dynamic_array(path),
+ __get_dynamic_array_len(path));
+ else
+ __assign_str(path, "(null)");
+ ),
+
+ TP_printk("root=%d id=%d level=%d path=%s",
+ __entry->root, __entry->id, __entry->level, __get_str(path))
+);
+
+DEFINE_EVENT(cgroup, cgroup_mkdir,
+
+ TP_PROTO(struct cgroup *cgroup),
+
+ TP_ARGS(cgroup)
+);
+
+DEFINE_EVENT(cgroup, cgroup_rmdir,
+
+ TP_PROTO(struct cgroup *cgroup),
+
+ TP_ARGS(cgroup)
+);
+
+DEFINE_EVENT(cgroup, cgroup_release,
+
+ TP_PROTO(struct cgroup *cgroup),
+
+ TP_ARGS(cgroup)
+);
+
+DEFINE_EVENT(cgroup, cgroup_rename,
+
+ TP_PROTO(struct cgroup *cgroup),
+
+ TP_ARGS(cgroup)
+);
+
+DECLARE_EVENT_CLASS(cgroup_migrate,
+
+ TP_PROTO(struct cgroup *dst_cgrp, struct task_struct *task, bool threadgroup),
+
+ TP_ARGS(dst_cgrp, task, threadgroup),
+
+ TP_STRUCT__entry(
+ __field( int, dst_root )
+ __field( int, dst_id )
+ __field( int, dst_level )
+ __dynamic_array(char, dst_path,
+ dst_cgrp->kn ? cgroup_path(dst_cgrp, NULL, 0) + 1
+ : strlen("(null)"))
+ __field( int, pid )
+ __string( comm, task->comm )
+ ),
+
+ TP_fast_assign(
+ __entry->dst_root = dst_cgrp->root->hierarchy_id;
+ __entry->dst_id = dst_cgrp->id;
+ __entry->dst_level = dst_cgrp->level;
+ if (dst_cgrp->kn)
+ cgroup_path(dst_cgrp, __get_dynamic_array(dst_path),
+ __get_dynamic_array_len(dst_path));
+ else
+ __assign_str(dst_path, "(null)");
+ __entry->pid = task->pid;
+ __assign_str(comm, task->comm);
+ ),
+
+ TP_printk("dst_root=%d dst_id=%d dst_level=%d dst_path=%s pid=%d comm=%s",
+ __entry->dst_root, __entry->dst_id, __entry->dst_level,
+ __get_str(dst_path), __entry->pid, __get_str(comm))
+);
+
+DEFINE_EVENT(cgroup_migrate, cgroup_attach_task,
+
+ TP_PROTO(struct cgroup *dst_cgrp, struct task_struct *task, bool threadgroup),
+
+ TP_ARGS(dst_cgrp, task, threadgroup)
+);
+
+DEFINE_EVENT(cgroup_migrate, cgroup_transfer_tasks,
+
+ TP_PROTO(struct cgroup *dst_cgrp, struct task_struct *task, bool threadgroup),
+
+ TP_ARGS(dst_cgrp, task, threadgroup)
+);
+
+#endif /* _TRACE_CGROUP_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 3861161..5e2e81a 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -64,6 +64,9 @@
#include <linux/file.h>
#include <net/sock.h>

+#define CREATE_TRACE_POINTS
+#include <trace/events/cgroup.h>
+
/*
* pidlists linger the following amount before being destroyed. The goal
* is avoiding frequent destruction in the middle of consecutive read calls
@@ -1176,6 +1179,8 @@ static void cgroup_destroy_root(struct cgroup_root *root)
struct cgroup *cgrp = &root->cgrp;
struct cgrp_cset_link *link, *tmp_link;

+ trace_cgroup_destroy_root(root);
+
cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);

BUG_ON(atomic_read(&root->nr_cgrps));
@@ -1874,6 +1879,9 @@ static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data)
strcpy(root->release_agent_path, opts.release_agent);
spin_unlock(&release_agent_path_lock);
}
+
+ trace_cgroup_remount(root);
+
out_unlock:
kfree(opts.release_agent);
kfree(opts.name);
@@ -2031,6 +2039,8 @@ static int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
if (ret)
goto destroy_root;

+ trace_cgroup_setup_root(root);
+
/*
* There must be no failure case after here, since rebinding takes
* care of subsystems' refcounts, which are explicitly dropped in
@@ -2825,6 +2835,10 @@ static int cgroup_attach_task(struct cgroup *dst_cgrp,
ret = cgroup_migrate(leader, threadgroup, dst_cgrp->root);

cgroup_migrate_finish(&preloaded_csets);
+
+ if (!ret)
+ trace_cgroup_attach_task(dst_cgrp, leader, threadgroup);
+
return ret;
}

@@ -3587,6 +3601,8 @@ static int cgroup_rename(struct kernfs_node *kn, struct kernfs_node *new_parent,
mutex_lock(&cgroup_mutex);

ret = kernfs_rename(kn, new_parent, new_name_str);
+ if (!ret)
+ trace_cgroup_rename(cgrp);

mutex_unlock(&cgroup_mutex);

@@ -4355,6 +4371,8 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)

if (task) {
ret = cgroup_migrate(task, false, to->root);
+ if (!ret)
+ trace_cgroup_transfer_tasks(to, task, false);
put_task_struct(task);
}
} while (task && !ret);
@@ -5020,6 +5038,8 @@ static void css_release_work_fn(struct work_struct *work)
ss->css_released(css);
} else {
/* cgroup release path */
+ trace_cgroup_release(cgrp);
+
cgroup_idr_remove(&cgrp->root->cgroup_idr, cgrp->id);
cgrp->id = -1;

@@ -5306,6 +5326,8 @@ static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
if (ret)
goto out_destroy;

+ trace_cgroup_mkdir(cgrp);
+
/* let's create and online css's */
kernfs_activate(kn);

@@ -5481,6 +5503,9 @@ static int cgroup_rmdir(struct kernfs_node *kn)

ret = cgroup_destroy_locked(cgrp);

+ if (!ret)
+ trace_cgroup_rmdir(cgrp);
+
cgroup_kn_unlock(kn);
return ret;
}
--
2.7.4
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