Task Control Groups: simple task cgroup debug info subsystem

This example subsystem exports debugging information as an aid to diagnosing
refcount leaks, etc, in the cgroup framework.

Signed-off-by: Paul Menage <menage@google.com>
Cc: Serge E. Hallyn <serue@us.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: Kirill Korotaev <dev@openvz.org>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h
index a568b87..cbadc3b 100644 (file)
--- a/include/linux/cgroup_subsys.h
+++ b/include/linux/cgroup_subsys.h
@@ -19,4 +19,8 @@ SUBSYS(cpuacct)
 
 /* */
 
+#ifdef CONFIG_CGROUP_DEBUG
+SUBSYS(debug)
+#endif
+
 /* */

diff --git a/init/Kconfig b/init/Kconfig
index b59a0a9..6687f80 100644 (file)
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -278,6 +278,16 @@ config CGROUPS
 
          Say N if unsure.
 
+config CGROUP_DEBUG
+       bool "Example debug cgroup subsystem"
+       depends on CGROUPS
+       help
+         This option enables a simple cgroup subsystem that
+         exports useful debugging information about the cgroups
+         framework
+
+         Say N if unsure
+
 config CPUSETS
        bool "Cpuset support"
        depends on SMP && CGROUPS

diff --git a/kernel/Makefile b/kernel/Makefile
index 48a7fae..a50a6de 100644 (file)
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -37,6 +37,7 @@ obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
 obj-$(CONFIG_KEXEC) += kexec.o
 obj-$(CONFIG_COMPAT) += compat.o
 obj-$(CONFIG_CGROUPS) += cgroup.o
+obj-$(CONFIG_CGROUP_DEBUG) += cgroup_debug.o
 obj-$(CONFIG_CPUSETS) += cpuset.o
 obj-$(CONFIG_CGROUP_CPUACCT) += cpu_acct.o
 obj-$(CONFIG_IKCONFIG) += configs.o

diff --git a/kernel/cgroup_debug.c b/kernel/cgroup_debug.c
new file mode 100644 (file)
index 0000000..37301e8
--- /dev/null
+++ b/kernel/cgroup_debug.c
@@ -0,0 +1,97 @@
+/*
+ * kernel/ccontainer_debug.c - Example cgroup subsystem that
+ * exposes debug info
+ *
+ * Copyright (C) Google Inc, 2007
+ *
+ * Developed by Paul Menage (menage@google.com)
+ *
+ */
+
+#include <linux/cgroup.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/rcupdate.h>
+
+#include <asm/atomic.h>
+
+static struct cgroup_subsys_state *debug_create(struct cgroup_subsys *ss,
+                                                  struct cgroup *cont)
+{
+       struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);
+
+       if (!css)
+               return ERR_PTR(-ENOMEM);
+
+       return css;
+}
+
+static void debug_destroy(struct cgroup_subsys *ss, struct cgroup *cont)
+{
+       kfree(cont->subsys[debug_subsys_id]);
+}
+
+static u64 cgroup_refcount_read(struct cgroup *cont, struct cftype *cft)
+{
+       return atomic_read(&cont->count);
+}
+
+static u64 taskcount_read(struct cgroup *cont, struct cftype *cft)
+{
+       u64 count;
+
+       cgroup_lock();
+       count = cgroup_task_count(cont);
+       cgroup_unlock();
+       return count;
+}
+
+static u64 current_css_set_read(struct cgroup *cont, struct cftype *cft)
+{
+       return (u64)(long)current->cgroups;
+}
+
+static u64 current_css_set_refcount_read(struct cgroup *cont,
+                                          struct cftype *cft)
+{
+       u64 count;
+
+       rcu_read_lock();
+       count = atomic_read(&current->cgroups->ref.refcount);
+       rcu_read_unlock();
+       return count;
+}
+
+static struct cftype files[] =  {
+       {
+               .name = "cgroup_refcount",
+               .read_uint = cgroup_refcount_read,
+       },
+       {
+               .name = "taskcount",
+               .read_uint = taskcount_read,
+       },
+
+       {
+               .name = "current_css_set",
+               .read_uint = current_css_set_read,
+       },
+
+       {
+               .name = "current_css_set_refcount",
+               .read_uint = current_css_set_refcount_read,
+       },
+};
+
+static int debug_populate(struct cgroup_subsys *ss, struct cgroup *cont)
+{
+       return cgroup_add_files(cont, ss, files, ARRAY_SIZE(files));
+}
+
+struct cgroup_subsys debug_subsys = {
+       .name = "debug",
+       .create = debug_create,
+       .destroy = debug_destroy,
+       .populate = debug_populate,
+       .subsys_id = debug_subsys_id,
+};