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, 176 insertions, 0 deletions

diff --git a/Documentation/maintainer/pull-requests.rst b/Documentation/maintainer/pull-requests.rst
new file mode 100644
index 000000000..0d63d9d7e
--- /dev/null
+++ b/Documentation/maintainer/pull-requests.rst
@@ -0,0 +1,176 @@
+Creating Pull Requests
+======================
+
+This chapter describes how maintainers can create and submit pull requests
+to other maintainers. This is useful for transferring changes from one
+maintainers tree to another maintainers tree.
+
+This document was written by Tobin C. Harding (who at that time, was not an
+experienced maintainer) primarily from comments made by Greg Kroah-Hartman
+and Linus Torvalds on LKML. Suggestions and fixes by Jonathan Corbet and
+Mauro Carvalho Chehab.  Misrepresentation was unintentional but inevitable,
+please direct abuse to Tobin C. Harding <me@tobin.cc>.
+
+Original email thread::
+
+	https://lore.kernel.org/r/20171114110500.GA21175@kroah.com
+
+
+Create Branch
+-------------
+
+To start with you will need to have all the changes you wish to include in
+the pull request on a separate branch. Typically you will base this branch
+off of a branch in the developers tree whom you intend to send the pull
+request to.
+
+In order to create the pull request you must first tag the branch that you
+have just created. It is recommended that you choose a meaningful tag name,
+in a way that you and others can understand, even after some time.  A good
+practice is to include in the name an indicator of the subsystem of origin
+and the target kernel version.
+
+Greg offers the following. A pull request with miscellaneous stuff for
+drivers/char, to be applied at the Kernel version 4.15-rc1 could be named
+as ``char-misc-4.15-rc1``. If such tag would be produced from a branch
+named ``char-misc-next``, you would be using the following command::
+
+        git tag -s char-misc-4.15-rc1 char-misc-next
+
+that will create a signed tag called ``char-misc-4.15-rc1`` based on the
+last commit in the ``char-misc-next`` branch, and sign it with your gpg key
+(see Documentation/maintainer/configure-git.rst).
+
+Linus will only accept pull requests based on a signed tag. Other
+maintainers may differ.
+
+When you run the above command ``git`` will drop you into an editor and ask
+you to describe the tag.  In this case, you are describing a pull request,
+so outline what is contained here, why it should be merged, and what, if
+any, testing has been done.  All of this information will end up in the tag
+itself, and then in the merge commit that the maintainer makes if/when they
+merge the pull request. So write it up well, as it will be in the kernel
+tree forever.
+
+As said by Linus::
+
+	Anyway, at least to me, the important part is the *message*. I want
+	to understand what I'm pulling, and why I should pull it. I also
+	want to use that message as the message for the merge, so it should
+	not just make sense to me, but make sense as a historical record
+	too.
+
+	Note that if there is something odd about the pull request, that
+	should very much be in the explanation. If you're touching files
+	that you don't maintain, explain _why_. I will see it in the
+	diffstat anyway, and if you didn't mention it, I'll just be extra
+	suspicious.  And when you send me new stuff after the merge window
+	(or even bug-fixes, but ones that look scary), explain not just
+	what they do and why they do it, but explain the _timing_. What
+	happened that this didn't go through the merge window..
+
+	I will take both what you write in the email pull request _and_ in
+	the signed tag, so depending on your workflow, you can either
+	describe your work in the signed tag (which will also automatically
+	make it into the pull request email), or you can make the signed
+	tag just a placeholder with nothing interesting in it, and describe
+	the work later when you actually send me the pull request.
+
+	And yes, I will edit the message. Partly because I tend to do just
+	trivial formatting (the whole indentation and quoting etc), but
+	partly because part of the message may make sense for me at pull
+	time (describing the conflicts and your personal issues for sending
+	it right now), but may not make sense in the context of a merge
+	commit message, so I will try to make it all make sense. I will
+	also fix any speeling mistaeks and bad grammar I notice,
+	particularly for non-native speakers (but also for native ones
+	;^). But I may miss some, or even add some.
+
+			Linus
+
+Greg gives, as an example pull request::
+
+	Char/Misc patches for 4.15-rc1
+
+	Here is the big char/misc patch set for the 4.15-rc1 merge window.
+	Contained in here is the normal set of new functions added to all
+	of these crazy drivers, as well as the following brand new
+	subsystems:
+		- time_travel_controller: Finally a set of drivers for the
+		  latest time travel bus architecture that provides i/o to
+		  the CPU before it asked for it, allowing uninterrupted
+		  processing
+		- relativity_shifters: due to the affect that the
+		  time_travel_controllers have on the overall system, there
+		  was a need for a new set of relativity shifter drivers to
+		  accommodate the newly formed black holes that would
+		  threaten to suck CPUs into them.  This subsystem handles
+		  this in a way to successfully neutralize the problems.
+		  There is a Kconfig option to force these to be enabled
+		  when needed, so problems should not occur.
+
+	All of these patches have been successfully tested in the latest
+	linux-next releases, and the original problems that it found have
+	all been resolved (apologies to anyone living near Canberra for the
+	lack of the Kconfig options in the earlier versions of the
+	linux-next tree creations.)
+
+	Signed-off-by: Your-name-here <your_email@domain>
+
+
+The tag message format is just like a git commit id.  One line at the top
+for a "summary subject" and be sure to sign-off at the bottom.
+
+Now that you have a local signed tag, you need to push it up to where it
+can be retrieved::
+
+	git push origin char-misc-4.15-rc1
+
+
+Create Pull Request
+-------------------
+
+The last thing to do is create the pull request message.  ``git`` handily
+will do this for you with the ``git request-pull`` command, but it needs a
+bit of help determining what you want to pull, and on what to base the pull
+against (to show the correct changes to be pulled and the diffstat). The
+following command(s) will generate a pull request::
+
+	git request-pull master git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git/ char-misc-4.15-rc1
+
+Quoting Greg::
+
+	This is asking git to compare the difference from the
+	'char-misc-4.15-rc1' tag location, to the head of the 'master'
+	branch (which in my case points to the last location in Linus's
+	tree that I diverged from, usually a -rc release) and to use the
+	git:// protocol to pull from.  If you wish to use https://, that
+	can be used here instead as well (but note that some people behind
+	firewalls will have problems with https git pulls).
+
+	If the char-misc-4.15-rc1 tag is not present in the repo that I am
+	asking to be pulled from, git will complain saying it is not there,
+	a handy way to remember to actually push it to a public location.
+
+	The output of 'git request-pull' will contain the location of the
+	git tree and specific tag to pull from, and the full text
+	description of that tag (which is why you need to provide good
+	information in that tag).  It will also create a diffstat of the
+	pull request, and a shortlog of the individual commits that the
+	pull request will provide.
+
+Linus responded that he tends to prefer the ``git://`` protocol. Other
+maintainers may have different preferences. Also, note that if you are
+creating pull requests without a signed tag then ``https://`` may be a
+better choice. Please see the original thread for the full discussion.
+
+
+Submit Pull Request
+-------------------
+
+A pull request is submitted in the same way as an ordinary patch. Send as
+inline email to the maintainer and CC LKML and any sub-system specific
+lists if required. Pull requests to Linus typically have a subject line
+something like::
+
+	[GIT PULL] <subsystem> changes for v4.15-rc1