Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 165 insertions, 0 deletions

diff --git a/Documentation/usb/gadget_multi.rst b/Documentation/usb/gadget_multi.rst
new file mode 100644
index 000000000..f78a51ff2
--- /dev/null
+++ b/Documentation/usb/gadget_multi.rst
@@ -0,0 +1,165 @@
+==============================
+Multifunction Composite Gadget
+==============================
+
+Overview
+========
+
+The Multifunction Composite Gadget (or g_multi) is a composite gadget
+that makes extensive use of the composite framework to provide
+a... multifunction gadget.
+
+In its standard configuration it provides a single USB configuration
+with RNDIS[1] (that is Ethernet), USB CDC[2] ACM (that is serial) and
+USB Mass Storage functions.
+
+A CDC ECM (Ethernet) function may be turned on via a Kconfig option
+and RNDIS can be turned off.  If they are both enabled the gadget will
+have two configurations -- one with RNDIS and another with CDC ECM[3].
+
+Please note that if you use non-standard configuration (that is enable
+CDC ECM) you may need to change vendor and/or product ID.
+
+Host drivers
+============
+
+To make use of the gadget one needs to make it work on host side --
+without that there's no hope of achieving anything with the gadget.
+As one might expect, things one need to do very from system to system.
+
+Linux host drivers
+------------------
+
+Since the gadget uses standard composite framework and appears as such
+to Linux host it does not need any additional drivers on Linux host
+side.  All the functions are handled by respective drivers developed
+for them.
+
+This is also true for two configuration set-up with RNDIS
+configuration being the first one.  Linux host will use the second
+configuration with CDC ECM which should work better under Linux.
+
+Windows host drivers
+--------------------
+
+For the gadget to work under Windows two conditions have to be met:
+
+Detecting as composite gadget
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+First of all, Windows need to detect the gadget as an USB composite
+gadget which on its own have some conditions[4].  If they are met,
+Windows lets USB Generic Parent Driver[5] handle the device which then
+tries to match drivers for each individual interface (sort of, don't
+get into too many details).
+
+The good news is: you do not have to worry about most of the
+conditions!
+
+The only thing to worry is that the gadget has to have a single
+configuration so a dual RNDIS and CDC ECM gadget won't work unless you
+create a proper INF -- and of course, if you do submit it!
+
+Installing drivers for each function
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The other, trickier thing is making Windows install drivers for each
+individual function.
+
+For mass storage it is trivial since Windows detect it's an interface
+implementing USB Mass Storage class and selects appropriate driver.
+
+Things are harder with RDNIS and CDC ACM.
+
+RNDIS
+.....
+
+To make Windows select RNDIS drivers for the first function in the
+gadget, one needs to use the [[file:linux.inf]] file provided with this
+document.  It "attaches" Window's RNDIS driver to the first interface
+of the gadget.
+
+Please note, that while testing we encountered some issues[6] when
+RNDIS was not the first interface.  You do not need to worry abut it
+unless you are trying to develop your own gadget in which case watch
+out for this bug.
+
+CDC ACM
+.......
+
+Similarly, [[file:linux-cdc-acm.inf]] is provided for CDC ACM.
+
+Customising the gadget
+......................
+
+If you intend to hack the g_multi gadget be advised that rearranging
+functions will obviously change interface numbers for each of the
+functionality.  As an effect provided INFs won't work since they have
+interface numbers hard-coded in them (it's not hard to change those
+though[7]).
+
+This also means, that after experimenting with g_multi and changing
+provided functions one should change gadget's vendor and/or product ID
+so there will be no collision with other customised gadgets or the
+original gadget.
+
+Failing to comply may cause brain damage after wondering for hours why
+things don't work as intended before realising Windows have cached
+some drivers information (changing USB port may sometimes help plus
+you might try using USBDeview[8] to remove the phantom device).
+
+INF testing
+...........
+
+Provided INF files have been tested on Windows XP SP3, Windows Vista
+and Windows 7, all 32-bit versions.  It should work on 64-bit versions
+as well.  It most likely won't work on Windows prior to Windows XP
+SP2.
+
+Other systems
+-------------
+
+At this moment, drivers for any other systems have not been tested.
+Knowing how MacOS is based on BSD and BSD is an Open Source it is
+believed that it should (read: "I have no idea whether it will") work
+out-of-the-box.
+
+For more exotic systems I have even less to say...
+
+Any testing and drivers *are* *welcome*!
+
+Authors
+=======
+
+This document has been written by Michal Nazarewicz
+([[mailto:mina86@mina86.com]]).  INF files have been hacked with
+support of Marek Szyprowski ([[mailto:m.szyprowski@samsung.com]]) and
+Xiaofan Chen ([[mailto:xiaofanc@gmail.com]]) basing on the MS RNDIS
+template[9], Microchip's CDC ACM INF file and David Brownell's
+([[mailto:dbrownell@users.sourceforge.net]]) original INF files.
+
+Footnotes
+=========
+
+[1] Remote Network Driver Interface Specification,
+[[https://msdn.microsoft.com/en-us/library/ee484414.aspx]].
+
+[2] Communications Device Class Abstract Control Model, spec for this
+and other USB classes can be found at
+[[http://www.usb.org/developers/devclass_docs/]].
+
+[3] CDC Ethernet Control Model.
+
+[4] [[https://msdn.microsoft.com/en-us/library/ff537109(v=VS.85).aspx]]
+
+[5] [[https://msdn.microsoft.com/en-us/library/ff539234(v=VS.85).aspx]]
+
+[6] To put it in some other nice words, Windows failed to respond to
+any user input.
+
+[7] You may find [[http://www.cygnal.org/ubb/Forum9/HTML/001050.html]]
+useful.
+
+[8] https://www.nirsoft.net/utils/usb_devices_view.html
+
+[9] [[https://msdn.microsoft.com/en-us/library/ff570620.aspx]]