Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

1 files changed, 368 insertions, 0 deletions

diff --git a/Documentation/process/5.Posting.rst b/Documentation/process/5.Posting.rst
new file mode 100644
index 000000000..07d7dbed1
--- /dev/null
+++ b/Documentation/process/5.Posting.rst
@@ -0,0 +1,368 @@
+.. _development_posting:
+
+Posting patches
+===============
+
+Sooner or later, the time comes when your work is ready to be presented to
+the community for review and, eventually, inclusion into the mainline
+kernel.  Unsurprisingly, the kernel development community has evolved a set
+of conventions and procedures which are used in the posting of patches;
+following them will make life much easier for everybody involved.  This
+document will attempt to cover these expectations in reasonable detail;
+more information can also be found in the files
+:ref:`Documentation/process/submitting-patches.rst <submittingpatches>`
+and :ref:`Documentation/process/submit-checklist.rst <submitchecklist>`.
+
+
+When to post
+------------
+
+There is a constant temptation to avoid posting patches before they are
+completely "ready."  For simple patches, that is not a problem.  If the
+work being done is complex, though, there is a lot to be gained by getting
+feedback from the community before the work is complete.  So you should
+consider posting in-progress work, or even making a git tree available so
+that interested developers can catch up with your work at any time.
+
+When posting code which is not yet considered ready for inclusion, it is a
+good idea to say so in the posting itself.  Also mention any major work
+which remains to be done and any known problems.  Fewer people will look at
+patches which are known to be half-baked, but those who do will come in
+with the idea that they can help you drive the work in the right direction.
+
+
+Before creating patches
+-----------------------
+
+There are a number of things which should be done before you consider
+sending patches to the development community.  These include:
+
+ - Test the code to the extent that you can.  Make use of the kernel's
+   debugging tools, ensure that the kernel will build with all reasonable
+   combinations of configuration options, use cross-compilers to build for
+   different architectures, etc. Add tests, likely using an existing
+   testing framework like KUnit, and include them as a separate member
+   of your series (see the next section for more about patch series).
+   Note that this may be mandatory when affecting some subsystems. For
+   example, library functions (resides under lib/) are extensively used
+   almost everywhere and expected to be tested appropriately.
+
+ - Make sure your code is compliant with the kernel coding style
+   guidelines.
+
+ - Does your change have performance implications?  If so, you should run
+   benchmarks showing what the impact (or benefit) of your change is; a
+   summary of the results should be included with the patch.
+
+ - Be sure that you have the right to post the code.  If this work was done
+   for an employer, the employer likely has a right to the work and must be
+   agreeable with its release under the GPL.
+
+As a general rule, putting in some extra thought before posting code almost
+always pays back the effort in short order.
+
+
+Patch preparation
+-----------------
+
+The preparation of patches for posting can be a surprising amount of work,
+but, once again, attempting to save time here is not generally advisable
+even in the short term.
+
+Patches must be prepared against a specific version of the kernel.  As a
+general rule, a patch should be based on the current mainline as found in
+Linus's git tree.  When basing on mainline, start with a well-known release
+point - a stable or -rc release - rather than branching off the mainline at
+an arbitrary spot.
+
+It may become necessary to make versions against -mm, linux-next, or a
+subsystem tree, though, to facilitate wider testing and review.  Depending
+on the area of your patch and what is going on elsewhere, basing a patch
+against these other trees can require a significant amount of work
+resolving conflicts and dealing with API changes.
+
+Only the most simple changes should be formatted as a single patch;
+everything else should be made as a logical series of changes.  Splitting
+up patches is a bit of an art; some developers spend a long time figuring
+out how to do it in the way that the community expects.  There are a few
+rules of thumb, however, which can help considerably:
+
+ - The patch series you post will almost certainly not be the series of
+   changes found in your working revision control system.  Instead, the
+   changes you have made need to be considered in their final form, then
+   split apart in ways which make sense.  The developers are interested in
+   discrete, self-contained changes, not the path you took to get to those
+   changes.
+
+ - Each logically independent change should be formatted as a separate
+   patch.  These changes can be small ("add a field to this structure") or
+   large (adding a significant new driver, for example), but they should be
+   conceptually small and amenable to a one-line description.  Each patch
+   should make a specific change which can be reviewed on its own and
+   verified to do what it says it does.
+
+ - As a way of restating the guideline above: do not mix different types of
+   changes in the same patch.  If a single patch fixes a critical security
+   bug, rearranges a few structures, and reformats the code, there is a
+   good chance that it will be passed over and the important fix will be
+   lost.
+
+ - Each patch should yield a kernel which builds and runs properly; if your
+   patch series is interrupted in the middle, the result should still be a
+   working kernel.  Partial application of a patch series is a common
+   scenario when the "git bisect" tool is used to find regressions; if the
+   result is a broken kernel, you will make life harder for developers and
+   users who are engaging in the noble work of tracking down problems.
+
+ - Do not overdo it, though.  One developer once posted a set of edits
+   to a single file as 500 separate patches - an act which did not make him
+   the most popular person on the kernel mailing list.  A single patch can
+   be reasonably large as long as it still contains a single *logical*
+   change.
+
+ - It can be tempting to add a whole new infrastructure with a series of
+   patches, but to leave that infrastructure unused until the final patch
+   in the series enables the whole thing.  This temptation should be
+   avoided if possible; if that series adds regressions, bisection will
+   finger the last patch as the one which caused the problem, even though
+   the real bug is elsewhere.  Whenever possible, a patch which adds new
+   code should make that code active immediately.
+
+Working to create the perfect patch series can be a frustrating process
+which takes quite a bit of time and thought after the "real work" has been
+done.  When done properly, though, it is time well spent.
+
+
+Patch formatting and changelogs
+-------------------------------
+
+So now you have a perfect series of patches for posting, but the work is
+not done quite yet.  Each patch needs to be formatted into a message which
+quickly and clearly communicates its purpose to the rest of the world.  To
+that end, each patch will be composed of the following:
+
+ - An optional "From" line naming the author of the patch.  This line is
+   only necessary if you are passing on somebody else's patch via email,
+   but it never hurts to add it when in doubt.
+
+ - A one-line description of what the patch does.  This message should be
+   enough for a reader who sees it with no other context to figure out the
+   scope of the patch; it is the line that will show up in the "short form"
+   changelogs.  This message is usually formatted with the relevant
+   subsystem name first, followed by the purpose of the patch.  For
+   example:
+
+   ::
+
+	gpio: fix build on CONFIG_GPIO_SYSFS=n
+
+ - A blank line followed by a detailed description of the contents of the
+   patch.  This description can be as long as is required; it should say
+   what the patch does and why it should be applied to the kernel.
+
+ - One or more tag lines, with, at a minimum, one Signed-off-by: line from
+   the author of the patch.  Tags will be described in more detail below.
+
+The items above, together, form the changelog for the patch.  Writing good
+changelogs is a crucial but often-neglected art; it's worth spending
+another moment discussing this issue.  When writing a changelog, you should
+bear in mind that a number of different people will be reading your words.
+These include subsystem maintainers and reviewers who need to decide
+whether the patch should be included, distributors and other maintainers
+trying to decide whether a patch should be backported to other kernels, bug
+hunters wondering whether the patch is responsible for a problem they are
+chasing, users who want to know how the kernel has changed, and more.  A
+good changelog conveys the needed information to all of these people in the
+most direct and concise way possible.
+
+To that end, the summary line should describe the effects of and motivation
+for the change as well as possible given the one-line constraint.  The
+detailed description can then amplify on those topics and provide any
+needed additional information.  If the patch fixes a bug, cite the commit
+which introduced the bug if possible (and please provide both the commit ID
+and the title when citing commits).  If a problem is associated with
+specific log or compiler output, include that output to help others
+searching for a solution to the same problem.  If the change is meant to
+support other changes coming in later patch, say so.  If internal APIs are
+changed, detail those changes and how other developers should respond.  In
+general, the more you can put yourself into the shoes of everybody who will
+be reading your changelog, the better that changelog (and the kernel as a
+whole) will be.
+
+Needless to say, the changelog should be the text used when committing the
+change to a revision control system.  It will be followed by:
+
+ - The patch itself, in the unified ("-u") patch format.  Using the "-p"
+   option to diff will associate function names with changes, making the
+   resulting patch easier for others to read.
+
+The tags already briefly mentioned above are used to provide insights how
+the patch came into being. They are described in detail in the
+:ref:`Documentation/process/submitting-patches.rst <submittingpatches>`
+document; what follows here is a brief summary.
+
+One tag is used to refer to earlier commits which introduced problems fixed by
+the patch::
+
+	Fixes: 1f2e3d4c5b6a ("The first line of the commit specified by the first 12 characters of its SHA-1 ID")
+
+Another tag is used for linking web pages with additional backgrounds or
+details, for example an earlier discussion which leads to the patch or a
+document with a specification implemented by the patch::
+
+	Link: https://example.com/somewhere.html  optional-other-stuff
+
+As per guidance from the Chief Penguin, a Link: tag should only be added to
+a commit if it leads to useful information that is not found in the commit
+itself.
+
+If the URL points to a public bug report being fixed by the patch, use the
+"Closes:" tag instead::
+
+	Closes: https://example.com/issues/1234  optional-other-stuff
+
+Some bug trackers have the ability to close issues automatically when a
+commit with such a tag is applied. Some bots monitoring mailing lists can
+also track such tags and take certain actions. Private bug trackers and
+invalid URLs are forbidden.
+
+Another kind of tag is used to document who was involved in the development of
+the patch. Each of these uses this format::
+
+	tag: Full Name <email address>  optional-other-stuff
+
+The tags in common use are:
+
+ - Signed-off-by: this is a developer's certification that he or she has
+   the right to submit the patch for inclusion into the kernel.  It is an
+   agreement to the Developer's Certificate of Origin, the full text of
+   which can be found in :ref:`Documentation/process/submitting-patches.rst <submittingpatches>`
+   Code without a proper signoff cannot be merged into the mainline.
+
+ - Co-developed-by: states that the patch was co-created by several developers;
+   it is a used to give attribution to co-authors (in addition to the author
+   attributed by the From: tag) when multiple people work on a single patch.
+   Every Co-developed-by: must be immediately followed by a Signed-off-by: of
+   the associated co-author.  Details and examples can be found in
+   :ref:`Documentation/process/submitting-patches.rst <submittingpatches>`.
+
+ - Acked-by: indicates an agreement by another developer (often a
+   maintainer of the relevant code) that the patch is appropriate for
+   inclusion into the kernel.
+
+ - Tested-by: states that the named person has tested the patch and found
+   it to work.
+
+ - Reviewed-by: the named developer has reviewed the patch for correctness;
+   see the reviewer's statement in :ref:`Documentation/process/submitting-patches.rst <submittingpatches>`
+   for more detail.
+
+ - Reported-by: names a user who reported a problem which is fixed by this
+   patch; this tag is used to give credit to the (often underappreciated)
+   people who test our code and let us know when things do not work
+   correctly. Note, this tag should be followed by a Closes: tag pointing to
+   the report, unless the report is not available on the web. The Link: tag
+   can be used instead of Closes: if the patch fixes a part of the issue(s)
+   being reported.
+
+ - A Suggested-by: tag indicates that the patch idea is suggested by the person
+   named and ensures credit to the person for the idea. This will, hopefully,
+   inspire them to help us again in the future.
+
+ - Cc: the named person received a copy of the patch and had the
+   opportunity to comment on it.
+
+Be careful in the addition of the aforementioned tags to your patches, as all
+except for Cc:, Reported-by:, and Suggested-by: need explicit permission of the
+person named. For those three implicit permission is sufficient if the person
+contributed to the Linux kernel using that name and email address according
+to the lore archives or the commit history -- and in case of Reported-by:
+and Suggested-by: did the reporting or suggestion in public. Note,
+bugzilla.kernel.org is a public place in this sense, but email addresses
+used there are private; so do not expose them in tags, unless the person
+used them in earlier contributions.
+
+
+Sending the patch
+-----------------
+
+Before you mail your patches, there are a couple of other things you should
+take care of:
+
+ - Are you sure that your mailer will not corrupt the patches?  Patches
+   which have had gratuitous white-space changes or line wrapping performed
+   by the mail client will not apply at the other end, and often will not
+   be examined in any detail.  If there is any doubt at all, mail the patch
+   to yourself and convince yourself that it shows up intact.
+
+   :ref:`Documentation/process/email-clients.rst <email_clients>` has some
+   helpful hints on making specific mail clients work for sending patches.
+
+ - Are you sure your patch is free of silly mistakes?  You should always
+   run patches through scripts/checkpatch.pl and address the complaints it
+   comes up with.  Please bear in mind that checkpatch.pl, while being the
+   embodiment of a fair amount of thought about what kernel patches should
+   look like, is not smarter than you.  If fixing a checkpatch.pl complaint
+   would make the code worse, don't do it.
+
+Patches should always be sent as plain text.  Please do not send them as
+attachments; that makes it much harder for reviewers to quote sections of
+the patch in their replies.  Instead, just put the patch directly into your
+message.
+
+When mailing patches, it is important to send copies to anybody who might
+be interested in it.  Unlike some other projects, the kernel encourages
+people to err on the side of sending too many copies; don't assume that the
+relevant people will see your posting on the mailing lists.  In particular,
+copies should go to:
+
+ - The maintainer(s) of the affected subsystem(s).  As described earlier,
+   the MAINTAINERS file is the first place to look for these people.
+
+ - Other developers who have been working in the same area - especially
+   those who might be working there now.  Using git to see who else has
+   modified the files you are working on can be helpful.
+
+ - If you are responding to a bug report or a feature request, copy the
+   original poster as well.
+
+ - Send a copy to the relevant mailing list, or, if nothing else applies,
+   the linux-kernel list.
+
+ - If you are fixing a bug, think about whether the fix should go into the
+   next stable update.  If so, stable@vger.kernel.org should get a copy of
+   the patch.  Also add a "Cc: stable@vger.kernel.org" to the tags within
+   the patch itself; that will cause the stable team to get a notification
+   when your fix goes into the mainline.
+
+When selecting recipients for a patch, it is good to have an idea of who
+you think will eventually accept the patch and get it merged.  While it
+is possible to send patches directly to Linus Torvalds and have him merge
+them, things are not normally done that way.  Linus is busy, and there are
+subsystem maintainers who watch over specific parts of the kernel.  Usually
+you will be wanting that maintainer to merge your patches.  If there is no
+obvious maintainer, Andrew Morton is often the patch target of last resort.
+
+Patches need good subject lines.  The canonical format for a patch line is
+something like:
+
+::
+
+	[PATCH nn/mm] subsys: one-line description of the patch
+
+where "nn" is the ordinal number of the patch, "mm" is the total number of
+patches in the series, and "subsys" is the name of the affected subsystem.
+Clearly, nn/mm can be omitted for a single, standalone patch.
+
+If you have a significant series of patches, it is customary to send an
+introductory description as part zero.  This convention is not universally
+followed though; if you use it, remember that information in the
+introduction does not make it into the kernel changelogs.  So please ensure
+that the patches, themselves, have complete changelog information.
+
+In general, the second and following parts of a multi-part patch should be
+sent as a reply to the first part so that they all thread together at the
+receiving end.  Tools like git and quilt have commands to mail out a set of
+patches with the proper threading.  If you have a long series, though, and
+are using git, please stay away from the --chain-reply-to option to avoid
+creating exceptionally deep nesting.