Merge git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core-2.6

[safe/jmp/linux-2.6] / include / linux / cgroup.h

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 7166023..e267e62 100644 (file)
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -14,6 +14,7 @@
 #include <linux/rcupdate.h>
 #include <linux/cgroupstats.h>
 #include <linux/prio_heap.h>
+#include <linux/rwsem.h>
 
 #ifdef CONFIG_CGROUPS
 
@@ -24,7 +25,6 @@ struct cgroup;
 
 extern int cgroup_init_early(void);
 extern int cgroup_init(void);
-extern void cgroup_init_smp(void);
 extern void cgroup_lock(void);
 extern bool cgroup_lock_live_group(struct cgroup *cgrp);
 extern void cgroup_unlock(void);
@@ -52,9 +52,9 @@ struct cgroup_subsys_state {
         * hierarchy structure */
        struct cgroup *cgroup;
 
-       /* State maintained by the cgroup system to allow
-        * subsystems to be "busy". Should be accessed via css_get()
-        * and css_put() */
+       /* State maintained by the cgroup system to allow subsystems
+        * to be "busy". Should be accessed via css_get(),
+        * css_tryget() and and css_put(). */
 
        atomic_t refcnt;
 
@@ -64,11 +64,14 @@ struct cgroup_subsys_state {
 /* bits in struct cgroup_subsys_state flags field */
 enum {
        CSS_ROOT, /* This CSS is the root of the subsystem */
+       CSS_REMOVED, /* This CSS is dead */
 };
 
 /*
- * Call css_get() to hold a reference on the cgroup;
- *
+ * Call css_get() to hold a reference on the css; it can be used
+ * for a reference obtained via:
+ * - an existing ref-counted reference to the css
+ * - task->cgroups for a locked task
  */
 
 static inline void css_get(struct cgroup_subsys_state *css)
@@ -77,9 +80,32 @@ static inline void css_get(struct cgroup_subsys_state *css)
        if (!test_bit(CSS_ROOT, &css->flags))
                atomic_inc(&css->refcnt);
 }
+
+static inline bool css_is_removed(struct cgroup_subsys_state *css)
+{
+       return test_bit(CSS_REMOVED, &css->flags);
+}
+
+/*
+ * Call css_tryget() to take a reference on a css if your existing
+ * (known-valid) reference isn't already ref-counted. Returns false if
+ * the css has been destroyed.
+ */
+
+static inline bool css_tryget(struct cgroup_subsys_state *css)
+{
+       if (test_bit(CSS_ROOT, &css->flags))
+               return true;
+       while (!atomic_inc_not_zero(&css->refcnt)) {
+               if (test_bit(CSS_REMOVED, &css->flags))
+                       return false;
+       }
+       return true;
+}
+
 /*
  * css_put() should be called to release a reference taken by
- * css_get()
+ * css_get() or css_tryget()
  */
 
 extern void __css_put(struct cgroup_subsys_state *css);
@@ -116,7 +142,7 @@ struct cgroup {
        struct list_head children;      /* my children */
 
        struct cgroup *parent;  /* my parent */
-       struct dentry *dentry;          /* cgroup fs entry */
+       struct dentry *dentry;          /* cgroup fs entry, RCU protected */
 
        /* Private pointers for each registered subsystem */
        struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
@@ -136,6 +162,18 @@ struct cgroup {
         * release_list_lock
         */
        struct list_head release_list;
+
+       /* pids_mutex protects the fields below */
+       struct rw_semaphore pids_mutex;
+       /* Array of process ids in the cgroup */
+       pid_t *tasks_pids;
+       /* How many files are using the current tasks_pids array */
+       int pids_use_count;
+       /* Length of the current tasks_pids array */
+       int pids_length;
+
+       /* For RCU-protected deletion */
+       struct rcu_head rcu_head;
 };
 
 /* A css_set is a structure holding pointers to a set of
@@ -320,13 +358,7 @@ struct cgroup_subsys {
                        struct cgroup *cgrp);
        void (*post_clone)(struct cgroup_subsys *ss, struct cgroup *cgrp);
        void (*bind)(struct cgroup_subsys *ss, struct cgroup *root);
-       /*
-        * This routine is called with the task_lock of mm->owner held
-        */
-       void (*mm_owner_changed)(struct cgroup_subsys *ss,
-                                       struct cgroup *old,
-                                       struct cgroup *new,
-                                       struct task_struct *p);
+
        int subsys_id;
        int active;
        int disabled;
@@ -334,12 +366,24 @@ struct cgroup_subsys {
 #define MAX_CGROUP_TYPE_NAMELEN 32
        const char *name;
 
-       /* Protected by RCU */
-       struct cgroupfs_root *root;
+       /*
+        * Protects sibling/children links of cgroups in this
+        * hierarchy, plus protects which hierarchy (or none) the
+        * subsystem is a part of (i.e. root/sibling).  To avoid
+        * potential deadlocks, the following operations should not be
+        * undertaken while holding any hierarchy_mutex:
+        *
+        * - allocating memory
+        * - initiating hotplug events
+        */
+       struct mutex hierarchy_mutex;
 
+       /*
+        * Link to parent, and list entry in parent's children.
+        * Protected by this->hierarchy_mutex and cgroup_lock()
+        */
+       struct cgroupfs_root *root;
        struct list_head sibling;
-
-       void *private;
 };
 
 #define SUBSYS(_x) extern struct cgroup_subsys _x ## _subsys;
@@ -397,7 +441,6 @@ int cgroup_attach_task(struct cgroup *, struct task_struct *);
 
 static inline int cgroup_init_early(void) { return 0; }
 static inline int cgroup_init(void) { return 0; }
-static inline void cgroup_init_smp(void) {}
 static inline void cgroup_fork(struct task_struct *p) {}
 static inline void cgroup_fork_callbacks(struct task_struct *p) {}
 static inline void cgroup_post_fork(struct task_struct *p) {}
@@ -413,13 +456,4 @@ static inline int cgroupstats_build(struct cgroupstats *stats,
 
 #endif /* !CONFIG_CGROUPS */
 
-#ifdef CONFIG_MM_OWNER
-extern void
-cgroup_mm_owner_callbacks(struct task_struct *old, struct task_struct *new);
-#else /* !CONFIG_MM_OWNER */
-static inline void
-cgroup_mm_owner_callbacks(struct task_struct *old, struct task_struct *new)
-{
-}
-#endif /* CONFIG_MM_OWNER */
 #endif /* _LINUX_CGROUP_H */