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, 271 insertions, 0 deletions

diff --git a/Documentation/driver-api/clk.rst b/Documentation/driver-api/clk.rst
new file mode 100644
index 000000000..294ead519
--- /dev/null
+++ b/Documentation/driver-api/clk.rst
@@ -0,0 +1,271 @@
+========================
+The Common Clk Framework
+========================
+
+:Author: Mike Turquette <mturquette@ti.com>
+
+This document endeavours to explain the common clk framework details,
+and how to port a platform over to this framework.  It is not yet a
+detailed explanation of the clock api in include/linux/clk.h, but
+perhaps someday it will include that information.
+
+Introduction and interface split
+================================
+
+The common clk framework is an interface to control the clock nodes
+available on various devices today.  This may come in the form of clock
+gating, rate adjustment, muxing or other operations.  This framework is
+enabled with the CONFIG_COMMON_CLK option.
+
+The interface itself is divided into two halves, each shielded from the
+details of its counterpart.  First is the common definition of struct
+clk which unifies the framework-level accounting and infrastructure that
+has traditionally been duplicated across a variety of platforms.  Second
+is a common implementation of the clk.h api, defined in
+drivers/clk/clk.c.  Finally there is struct clk_ops, whose operations
+are invoked by the clk api implementation.
+
+The second half of the interface is comprised of the hardware-specific
+callbacks registered with struct clk_ops and the corresponding
+hardware-specific structures needed to model a particular clock.  For
+the remainder of this document any reference to a callback in struct
+clk_ops, such as .enable or .set_rate, implies the hardware-specific
+implementation of that code.  Likewise, references to struct clk_foo
+serve as a convenient shorthand for the implementation of the
+hardware-specific bits for the hypothetical "foo" hardware.
+
+Tying the two halves of this interface together is struct clk_hw, which
+is defined in struct clk_foo and pointed to within struct clk_core.  This
+allows for easy navigation between the two discrete halves of the common
+clock interface.
+
+Common data structures and api
+==============================
+
+.. kernel-doc:: drivers/clk/clk.c
+   :identifiers: struct clk_core
+
+The members above make up the core of the clk tree topology.  The clk
+api itself defines several driver-facing functions which operate on
+struct clk.  That api is documented in include/linux/clk.h.
+
+Platforms and devices utilizing the common struct clk_core use the struct
+clk_ops pointer in struct clk_core to perform the hardware-specific parts of
+the operations defined in clk-provider.h, and can set one or more
+framework-level flags documented below.
+
+.. kernel-doc:: include/linux/clk-provider.h
+   :identifiers: struct clk_ops
+
+Core flags
+==========
+
+.. kernel-doc:: include/linux/clk-provider.h
+   :doc: clk framework flags
+
+Hardware clk implementations
+============================
+
+The strength of the common struct clk_core comes from its .ops and .hw pointers
+which abstract the details of struct clk from the hardware-specific bits, and
+vice versa.  To illustrate consider the simple gateable clk implementation in
+drivers/clk/clk-gate.c::
+
+	struct clk_gate {
+		struct clk_hw	hw;
+		void __iomem    *reg;
+		u8              bit_idx;
+		...
+	};
+
+struct clk_gate contains struct clk_hw hw as well as hardware-specific
+knowledge about which register and bit controls this clk's gating.
+Nothing about clock topology or accounting, such as enable_count or
+notifier_count, is needed here.  That is all handled by the common
+framework code and struct clk_core.
+
+Let's walk through enabling this clk from driver code::
+
+	struct clk *clk;
+	clk = clk_get(NULL, "my_gateable_clk");
+
+	clk_prepare(clk);
+	clk_enable(clk);
+
+The call graph for clk_enable is very simple::
+
+	clk_enable(clk);
+		clk->ops->enable(clk->hw);
+		[resolves to...]
+			clk_gate_enable(hw);
+			[resolves struct clk gate with to_clk_gate(hw)]
+				clk_gate_set_bit(gate);
+
+And the definition of clk_gate_set_bit::
+
+	static void clk_gate_set_bit(struct clk_gate *gate)
+	{
+		u32 reg;
+
+		reg = __raw_readl(gate->reg);
+		reg |= BIT(gate->bit_idx);
+		writel(reg, gate->reg);
+	}
+
+Note that to_clk_gate is defined as::
+
+	#define to_clk_gate(_hw) container_of(_hw, struct clk_gate, hw)
+
+This pattern of abstraction is used for every clock hardware
+representation.
+
+Supporting your own clk hardware
+================================
+
+When implementing support for a new type of clock it is only necessary to
+include the following header::
+
+	#include <linux/clk-provider.h>
+
+To construct a clk hardware structure for your platform you must define
+the following::
+
+	struct clk_foo {
+		struct clk_hw hw;
+		... hardware specific data goes here ...
+	};
+
+To take advantage of your data you'll need to support valid operations
+for your clk::
+
+	struct clk_ops clk_foo_ops = {
+		.enable		= &clk_foo_enable,
+		.disable	= &clk_foo_disable,
+	};
+
+Implement the above functions using container_of::
+
+	#define to_clk_foo(_hw) container_of(_hw, struct clk_foo, hw)
+
+	int clk_foo_enable(struct clk_hw *hw)
+	{
+		struct clk_foo *foo;
+
+		foo = to_clk_foo(hw);
+
+		... perform magic on foo ...
+
+		return 0;
+	};
+
+Below is a matrix detailing which clk_ops are mandatory based upon the
+hardware capabilities of that clock.  A cell marked as "y" means
+mandatory, a cell marked as "n" implies that either including that
+callback is invalid or otherwise unnecessary.  Empty cells are either
+optional or must be evaluated on a case-by-case basis.
+
+.. table:: clock hardware characteristics
+
+   +----------------+------+-------------+---------------+-------------+------+
+   |                | gate | change rate | single parent | multiplexer | root |
+   +================+======+=============+===============+=============+======+
+   |.prepare        |      |             |               |             |      |
+   +----------------+------+-------------+---------------+-------------+------+
+   |.unprepare      |      |             |               |             |      |
+   +----------------+------+-------------+---------------+-------------+------+
+   +----------------+------+-------------+---------------+-------------+------+
+   |.enable         | y    |             |               |             |      |
+   +----------------+------+-------------+---------------+-------------+------+
+   |.disable        | y    |             |               |             |      |
+   +----------------+------+-------------+---------------+-------------+------+
+   |.is_enabled     | y    |             |               |             |      |
+   +----------------+------+-------------+---------------+-------------+------+
+   +----------------+------+-------------+---------------+-------------+------+
+   |.recalc_rate    |      | y           |               |             |      |
+   +----------------+------+-------------+---------------+-------------+------+
+   |.determine_rate |      | y           |               |             |      |
+   +----------------+------+-------------+---------------+-------------+------+
+   |.set_rate       |      | y           |               |             |      |
+   +----------------+------+-------------+---------------+-------------+------+
+   +----------------+------+-------------+---------------+-------------+------+
+   |.set_parent     |      |             | n             | y           | n    |
+   +----------------+------+-------------+---------------+-------------+------+
+   |.get_parent     |      |             | n             | y           | n    |
+   +----------------+------+-------------+---------------+-------------+------+
+   +----------------+------+-------------+---------------+-------------+------+
+   |.recalc_accuracy|      |             |               |             |      |
+   +----------------+------+-------------+---------------+-------------+------+
+   +----------------+------+-------------+---------------+-------------+------+
+   |.init           |      |             |               |             |      |
+   +----------------+------+-------------+---------------+-------------+------+
+
+Finally, register your clock at run-time with a hardware-specific
+registration function.  This function simply populates struct clk_foo's
+data and then passes the common struct clk parameters to the framework
+with a call to::
+
+	clk_register(...)
+
+See the basic clock types in ``drivers/clk/clk-*.c`` for examples.
+
+Disabling clock gating of unused clocks
+=======================================
+
+Sometimes during development it can be useful to be able to bypass the
+default disabling of unused clocks. For example, if drivers aren't enabling
+clocks properly but rely on them being on from the bootloader, bypassing
+the disabling means that the driver will remain functional while the issues
+are sorted out.
+
+You can see which clocks have been disabled by booting your kernel with these
+parameters::
+
+ tp_printk trace_event=clk:clk_disable
+
+To bypass this disabling, include "clk_ignore_unused" in the bootargs to the
+kernel.
+
+Locking
+=======
+
+The common clock framework uses two global locks, the prepare lock and the
+enable lock.
+
+The enable lock is a spinlock and is held across calls to the .enable,
+.disable operations. Those operations are thus not allowed to sleep,
+and calls to the clk_enable(), clk_disable() API functions are allowed in
+atomic context.
+
+For clk_is_enabled() API, it is also designed to be allowed to be used in
+atomic context. However, it doesn't really make any sense to hold the enable
+lock in core, unless you want to do something else with the information of
+the enable state with that lock held. Otherwise, seeing if a clk is enabled is
+a one-shot read of the enabled state, which could just as easily change after
+the function returns because the lock is released. Thus the user of this API
+needs to handle synchronizing the read of the state with whatever they're
+using it for to make sure that the enable state doesn't change during that
+time.
+
+The prepare lock is a mutex and is held across calls to all other operations.
+All those operations are allowed to sleep, and calls to the corresponding API
+functions are not allowed in atomic context.
+
+This effectively divides operations in two groups from a locking perspective.
+
+Drivers don't need to manually protect resources shared between the operations
+of one group, regardless of whether those resources are shared by multiple
+clocks or not. However, access to resources that are shared between operations
+of the two groups needs to be protected by the drivers. An example of such a
+resource would be a register that controls both the clock rate and the clock
+enable/disable state.
+
+The clock framework is reentrant, in that a driver is allowed to call clock
+framework functions from within its implementation of clock operations. This
+can for instance cause a .set_rate operation of one clock being called from
+within the .set_rate operation of another clock. This case must be considered
+in the driver implementations, but the code flow is usually controlled by the
+driver in that case.
+
+Note that locking must also be considered when code outside of the common
+clock framework needs to access resources used by the clock operations. This
+is considered out of scope of this document.