Merge tag 'armsoc-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc

[cascardo/linux.git] / kernel / relay.c

diff --git a/kernel/relay.c b/kernel/relay.c
index 04d7cf3..d797502 100644 (file)
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -451,6 +451,13 @@ static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
                if (!dentry)
                        goto free_buf;
                relay_set_buf_dentry(buf, dentry);
+       } else {
+               /* Only retrieve global info, nothing more, nothing less */
+               dentry = chan->cb->create_buf_file(NULL, NULL,
+                                                  S_IRUSR, buf,
+                                                  &chan->is_global);
+               if (WARN_ON(dentry))
+                       goto free_buf;
        }
 
        buf->cpu = cpu;
@@ -562,6 +569,10 @@ static int relay_hotcpu_callback(struct notifier_block *nb,
  *     attributes specified.  The created channel buffer files
  *     will be named base_filename0...base_filenameN-1.  File
  *     permissions will be %S_IRUSR.
+ *
+ *     If opening a buffer (@parent = NULL) that you later wish to register
+ *     in a filesystem, call relay_late_setup_files() once the @parent dentry
+ *     is available.
  */
 struct rchan *relay_open(const char *base_filename,
                         struct dentry *parent,
@@ -640,8 +651,12 @@ static void __relay_set_buf_dentry(void *info)
  *
  *     Returns 0 if successful, non-zero otherwise.
  *
- *     Use to setup files for a previously buffer-only channel.
- *     Useful to do early tracing in kernel, before VFS is up, for example.
+ *     Use to setup files for a previously buffer-only channel created
+ *     by relay_open() with a NULL parent dentry.
+ *
+ *     For example, this is useful for perfomring early tracing in kernel,
+ *     before VFS is up and then exposing the early results once the dentry
+ *     is available.
  */
 int relay_late_setup_files(struct rchan *chan,
                           const char *base_filename,
@@ -666,6 +681,20 @@ int relay_late_setup_files(struct rchan *chan,
        }
        chan->has_base_filename = 1;
        chan->parent = parent;
+
+       if (chan->is_global) {
+               err = -EINVAL;
+               if (!WARN_ON_ONCE(!chan->buf[0])) {
+                       dentry = relay_create_buf_file(chan, chan->buf[0], 0);
+                       if (dentry && !WARN_ON_ONCE(!chan->is_global)) {
+                               relay_set_buf_dentry(chan->buf[0], dentry);
+                               err = 0;
+                       }
+               }
+               mutex_unlock(&relay_channels_mutex);
+               return err;
+       }
+
        curr_cpu = get_cpu();
        /*
         * The CPU hotplug notifier ran before us and created buffers with
@@ -706,6 +735,7 @@ int relay_late_setup_files(struct rchan *chan,
 
        return err;
 }
+EXPORT_SYMBOL_GPL(relay_late_setup_files);
 
 /**
  *     relay_switch_subbuf - switch to a new sub-buffer