Merge branch 'for-4.19' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup updates from Tejun Heo:
 "Just one commit from Steven to take out spin lock from trace event
  handlers"

* 'for-4.19' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup/tracing: Move taking of spin lock out of trace event handlers

diff --git a/include/trace/events/cgroup.h b/include/trace/events/cgroup.h
index d74722c2ac8b18d02dc1c943937144f674212f52..a401ff5e784711e574233e74eddb3aec974fe522 100644 (file)
--- a/include/trace/events/cgroup.h
+++ b/include/trace/events/cgroup.h
@@ -53,24 +53,22 @@ DEFINE_EVENT(cgroup_root, cgroup_remount,
 
 DECLARE_EVENT_CLASS(cgroup,
 
-       TP_PROTO(struct cgroup *cgrp),
+       TP_PROTO(struct cgroup *cgrp, const char *path),
 
-       TP_ARGS(cgrp),
+       TP_ARGS(cgrp, path),
 
        TP_STRUCT__entry(
                __field(        int,            root                    )
                __field(        int,            id                      )
                __field(        int,            level                   )
-               __dynamic_array(char,           path,
-                               cgroup_path(cgrp, NULL, 0) + 1)
+               __string(       path,           path                    )
        ),
 
        TP_fast_assign(
                __entry->root = cgrp->root->hierarchy_id;
                __entry->id = cgrp->id;
                __entry->level = cgrp->level;
-               cgroup_path(cgrp, __get_dynamic_array(path),
-                                 __get_dynamic_array_len(path));
+               __assign_str(path, path);
        ),
 
        TP_printk("root=%d id=%d level=%d path=%s",
@@ -79,45 +77,45 @@ DECLARE_EVENT_CLASS(cgroup,
 
 DEFINE_EVENT(cgroup, cgroup_mkdir,
 
-       TP_PROTO(struct cgroup *cgroup),
+       TP_PROTO(struct cgroup *cgrp, const char *path),
 
-       TP_ARGS(cgroup)
+       TP_ARGS(cgrp, path)
 );
 
 DEFINE_EVENT(cgroup, cgroup_rmdir,
 
-       TP_PROTO(struct cgroup *cgroup),
+       TP_PROTO(struct cgroup *cgrp, const char *path),
 
-       TP_ARGS(cgroup)
+       TP_ARGS(cgrp, path)
 );
 
 DEFINE_EVENT(cgroup, cgroup_release,
 
-       TP_PROTO(struct cgroup *cgroup),
+       TP_PROTO(struct cgroup *cgrp, const char *path),
 
-       TP_ARGS(cgroup)
+       TP_ARGS(cgrp, path)
 );
 
 DEFINE_EVENT(cgroup, cgroup_rename,
 
-       TP_PROTO(struct cgroup *cgroup),
+       TP_PROTO(struct cgroup *cgrp, const char *path),
 
-       TP_ARGS(cgroup)
+       TP_ARGS(cgrp, path)
 );
 
 DECLARE_EVENT_CLASS(cgroup_migrate,
 
-       TP_PROTO(struct cgroup *dst_cgrp, struct task_struct *task, bool threadgroup),
+       TP_PROTO(struct cgroup *dst_cgrp, const char *path,
+                struct task_struct *task, bool threadgroup),
 
-       TP_ARGS(dst_cgrp, task, threadgroup),
+       TP_ARGS(dst_cgrp, path, task, threadgroup),
 
        TP_STRUCT__entry(
                __field(        int,            dst_root                )
                __field(        int,            dst_id                  )
                __field(        int,            dst_level               )
-               __dynamic_array(char,           dst_path,
-                               cgroup_path(dst_cgrp, NULL, 0) + 1)
                __field(        int,            pid                     )
+               __string(       dst_path,       path                    )
                __string(       comm,           task->comm              )
        ),
 
@@ -125,8 +123,7 @@ DECLARE_EVENT_CLASS(cgroup_migrate,
                __entry->dst_root = dst_cgrp->root->hierarchy_id;
                __entry->dst_id = dst_cgrp->id;
                __entry->dst_level = dst_cgrp->level;
-               cgroup_path(dst_cgrp, __get_dynamic_array(dst_path),
-                                     __get_dynamic_array_len(dst_path));
+               __assign_str(dst_path, path);
                __entry->pid = task->pid;
                __assign_str(comm, task->comm);
        ),
@@ -138,16 +135,18 @@ DECLARE_EVENT_CLASS(cgroup_migrate,
 
 DEFINE_EVENT(cgroup_migrate, cgroup_attach_task,
 
-       TP_PROTO(struct cgroup *dst_cgrp, struct task_struct *task, bool threadgroup),
+       TP_PROTO(struct cgroup *dst_cgrp, const char *path,
+                struct task_struct *task, bool threadgroup),
 
-       TP_ARGS(dst_cgrp, task, threadgroup)
+       TP_ARGS(dst_cgrp, path, task, threadgroup)
 );
 
 DEFINE_EVENT(cgroup_migrate, cgroup_transfer_tasks,
 
-       TP_PROTO(struct cgroup *dst_cgrp, struct task_struct *task, bool threadgroup),
+       TP_PROTO(struct cgroup *dst_cgrp, const char *path,
+                struct task_struct *task, bool threadgroup),
 
-       TP_ARGS(dst_cgrp, task, threadgroup)
+       TP_ARGS(dst_cgrp, path, task, threadgroup)
 );
 
 #endif /* _TRACE_CGROUP_H */

diff --git a/kernel/cgroup/cgroup-internal.h b/kernel/cgroup/cgroup-internal.h
index 77ff1cd6a25234c5b2f412c74da8e95eb539b8b6..75568fcf2180dd577f5e8e4903e30516d3c987db 100644 (file)
--- a/kernel/cgroup/cgroup-internal.h
+++ b/kernel/cgroup/cgroup-internal.h
@@ -8,6 +8,32 @@
 #include <linux/list.h>
 #include <linux/refcount.h>
 
+#define TRACE_CGROUP_PATH_LEN 1024
+extern spinlock_t trace_cgroup_path_lock;
+extern char trace_cgroup_path[TRACE_CGROUP_PATH_LEN];
+
+/*
+ * cgroup_path() takes a spin lock. It is good practice not to take
+ * spin locks within trace point handlers, as they are mostly hidden
+ * from normal view. As cgroup_path() can take the kernfs_rename_lock
+ * spin lock, it is best to not call that function from the trace event
+ * handler.
+ *
+ * Note: trace_cgroup_##type##_enabled() is a static branch that will only
+ *       be set when the trace event is enabled.
+ */
+#define TRACE_CGROUP_PATH(type, cgrp, ...)                             \
+       do {                                                            \
+               if (trace_cgroup_##type##_enabled()) {                  \
+                       spin_lock(&trace_cgroup_path_lock);             \
+                       cgroup_path(cgrp, trace_cgroup_path,            \
+                                   TRACE_CGROUP_PATH_LEN);             \
+                       trace_cgroup_##type(cgrp, trace_cgroup_path,    \
+                                           ##__VA_ARGS__);             \
+                       spin_unlock(&trace_cgroup_path_lock);           \
+               }                                                       \
+       } while (0)
+
 /*
  * A cgroup can be associated with multiple css_sets as different tasks may
  * belong to different cgroups on different hierarchies.  In the other

diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index 8b4f0768efd62244d3939b985059963371e04d63..51063e7a93c28a7c0ad5f8cca34072dffb85e650 100644 (file)
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -135,7 +135,7 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
                if (task) {
                        ret = cgroup_migrate(task, false, &mgctx);
                        if (!ret)
-                               trace_cgroup_transfer_tasks(to, task, false);
+                               TRACE_CGROUP_PATH(transfer_tasks, to, task, false);
                        put_task_struct(task);
                }
        } while (task && !ret);
@@ -865,7 +865,7 @@ static int cgroup1_rename(struct kernfs_node *kn, struct kernfs_node *new_parent
 
        ret = kernfs_rename(kn, new_parent, new_name_str);
        if (!ret)
-               trace_cgroup_rename(cgrp);
+               TRACE_CGROUP_PATH(rename, cgrp);
 
        mutex_unlock(&cgroup_mutex);
 

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 35cf3d71f8aaf4b7efcdc241953abe2108b58f6a..aae10baf1902af2099292856bf2e299f14edfd1f 100644 (file)
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -83,6 +83,9 @@ EXPORT_SYMBOL_GPL(cgroup_mutex);
 EXPORT_SYMBOL_GPL(css_set_lock);
 #endif
 
+DEFINE_SPINLOCK(trace_cgroup_path_lock);
+char trace_cgroup_path[TRACE_CGROUP_PATH_LEN];
+
 /*
  * Protects cgroup_idr and css_idr so that IDs can be released without
  * grabbing cgroup_mutex.
@@ -2638,7 +2641,7 @@ int cgroup_attach_task(struct cgroup *dst_cgrp, struct task_struct *leader,
        cgroup_migrate_finish(&mgctx);
 
        if (!ret)
-               trace_cgroup_attach_task(dst_cgrp, leader, threadgroup);
+               TRACE_CGROUP_PATH(attach_task, dst_cgrp, leader, threadgroup);
 
        return ret;
 }
@@ -4636,7 +4639,7 @@ static void css_release_work_fn(struct work_struct *work)
                struct cgroup *tcgrp;
 
                /* cgroup release path */
-               trace_cgroup_release(cgrp);
+               TRACE_CGROUP_PATH(release, cgrp);
 
                if (cgroup_on_dfl(cgrp))
                        cgroup_rstat_flush(cgrp);
@@ -4979,7 +4982,7 @@ int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, umode_t mode)
        if (ret)
                goto out_destroy;
 
-       trace_cgroup_mkdir(cgrp);
+       TRACE_CGROUP_PATH(mkdir, cgrp);
 
        /* let's create and online css's */
        kernfs_activate(kn);
@@ -5167,9 +5170,8 @@ int cgroup_rmdir(struct kernfs_node *kn)
                return 0;
 
        ret = cgroup_destroy_locked(cgrp);
-
        if (!ret)
-               trace_cgroup_rmdir(cgrp);
+               TRACE_CGROUP_PATH(rmdir, cgrp);
 
        cgroup_kn_unlock(kn);
        return ret;