workqueue: skip the node_nr_active update for non-unbound workqueuesgrafted

apply_wqattrs_commit() updates node_nr_active->max unconditionally.
wq->node_nr_active[] is only allocated for unbound workqueues, so guard
the call before per-cpu workqueues start using this path.

No functional change: only unbound workqueues reach apply_wqattrs_*()
today.

Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 66 insertions, 0 deletions

diff --git a/Documentation/trace/remotes.rst b/Documentation/trace/remotes.rst
new file mode 100644
index 000000000..1f9d764f6
--- /dev/null
+++ b/Documentation/trace/remotes.rst
@@ -0,0 +1,66 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===============
+Tracing Remotes
+===============
+
+:Author: Vincent Donnefort <vdonnefort@google.com>
+
+Overview
+========
+Firmware and hypervisors are black boxes to the kernel. Having a way to see what
+they are doing can be useful to debug both. This is where remote tracing buffers
+come in. A remote tracing buffer is a ring buffer executed by the firmware or
+hypervisor into memory that is memory mapped to the host kernel. This is similar
+to how user space memory maps the kernel ring buffer but in this case the kernel
+is acting like user space and the firmware or hypervisor is the "kernel" side.
+With a trace remote ring buffer, the firmware and hypervisor can record events
+for which the host kernel can see and expose to user space.
+
+Register a remote
+=================
+A remote must provide a set of callbacks `struct trace_remote_callbacks` whom
+description can be found below. Those callbacks allows Tracefs to enable and
+disable tracing and events, to load and unload a tracing buffer (a set of
+ring-buffers) and to swap a reader page with the head page, which enables
+consuming reading.
+
+.. kernel-doc:: include/linux/trace_remote.h
+
+Once registered, an instance will appear for this remote in the Tracefs
+directory **remotes/**. Buffers can then be read using the usual Tracefs files
+**trace_pipe** and **trace**.
+
+Declare a remote event
+======================
+Macros are provided to ease the declaration of remote events, in a similar
+fashion to in-kernel events. A declaration must provide an ID, a description of
+the event arguments and how to print the event:
+
+.. code-block:: c
+
+	REMOTE_EVENT(foo, EVENT_FOO_ID,
+		RE_STRUCT(
+			re_field(u64, bar)
+		),
+		RE_PRINTK("bar=%lld", __entry->bar)
+	);
+
+Then those events must be declared in a C file with the following:
+
+.. code-block:: c
+
+	#define REMOTE_EVENT_INCLUDE_FILE foo_events.h
+	#include <trace/define_remote_events.h>
+
+This will provide a `struct remote_event remote_event_foo` that can be given to
+`trace_remote_register`.
+
+Registered events appear in the remote directory under **events/**.
+
+Simple ring-buffer
+==================
+A simple implementation for a ring-buffer writer can be found in
+kernel/trace/simple_ring_buffer.c.
+
+.. kernel-doc:: include/linux/simple_ring_buffer.h