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

4 files changed, 116 insertions, 0 deletions

diff --git a/Documentation/arch/mips/booting.rst b/Documentation/arch/mips/booting.rst
new file mode 100644
index 000000000..7c18a4eab
--- /dev/null
+++ b/Documentation/arch/mips/booting.rst
@@ -0,0 +1,28 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+BMIPS DeviceTree Booting
+------------------------
+
+  Some bootloaders only support a single entry point, at the start of the
+  kernel image.  Other bootloaders will jump to the ELF start address.
+  Both schemes are supported; CONFIG_BOOT_RAW=y and CONFIG_NO_EXCEPT_FILL=y,
+  so the first instruction immediately jumps to kernel_entry().
+
+  Similar to the arch/arm case (b), a DT-aware bootloader is expected to
+  set up the following registers:
+
+         a0 : 0
+
+         a1 : 0xffffffff
+
+         a2 : Physical pointer to the device tree block (defined in chapter
+         II) in RAM.  The device tree can be located anywhere in the first
+         512MB of the physical address space (0x00000000 - 0x1fffffff),
+         aligned on a 64 bit boundary.
+
+  Legacy bootloaders do not use this convention, and they do not pass in a
+  DT block.  In this case, Linux will look for a builtin DTB, selected via
+  CONFIG_DT_*.
+
+  This convention is defined for 32-bit systems only, as there are not
+  currently any 64-bit BMIPS implementations.
diff --git a/Documentation/arch/mips/features.rst b/Documentation/arch/mips/features.rst
new file mode 100644
index 000000000..6e0ffe3e7
--- /dev/null
+++ b/Documentation/arch/mips/features.rst
@@ -0,0 +1,3 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+.. kernel-feat:: features mips
diff --git a/Documentation/arch/mips/index.rst b/Documentation/arch/mips/index.rst
new file mode 100644
index 000000000..703e195b9
--- /dev/null
+++ b/Documentation/arch/mips/index.rst
@@ -0,0 +1,14 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===========================
+MIPS-specific Documentation
+===========================
+
+.. toctree::
+   :maxdepth: 2
+   :numbered:
+
+   booting
+   ingenic-tcu
+
+   features
diff --git a/Documentation/arch/mips/ingenic-tcu.rst b/Documentation/arch/mips/ingenic-tcu.rst
new file mode 100644
index 000000000..2ce4cb131
--- /dev/null
+++ b/Documentation/arch/mips/ingenic-tcu.rst
@@ -0,0 +1,71 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===============================================
+Ingenic JZ47xx SoCs Timer/Counter Unit hardware
+===============================================
+
+The Timer/Counter Unit (TCU) in Ingenic JZ47xx SoCs is a multi-function
+hardware block. It features up to eight channels, that can be used as
+counters, timers, or PWM.
+
+- JZ4725B, JZ4750, JZ4755 only have six TCU channels. The other SoCs all
+  have eight channels.
+
+- JZ4725B introduced a separate channel, called Operating System Timer
+  (OST). It is a 32-bit programmable timer. On JZ4760B and above, it is
+  64-bit.
+
+- Each one of the TCU channels has its own clock, which can be reparented to three
+  different clocks (pclk, ext, rtc), gated, and reclocked, through their TCSR register.
+
+    - The watchdog and OST hardware blocks also feature a TCSR register with the same
+      format in their register space.
+    - The TCU registers used to gate/ungate can also gate/ungate the watchdog and
+      OST clocks.
+
+- Each TCU channel works in one of two modes:
+
+    - mode TCU1: channels cannot work in sleep mode, but are easier to
+      operate.
+    - mode TCU2: channels can work in sleep mode, but the operation is a bit
+      more complicated than with TCU1 channels.
+
+- The mode of each TCU channel depends on the SoC used:
+
+    - On the oldest SoCs (up to JZ4740), all of the eight channels operate in
+      TCU1 mode.
+    - On JZ4725B, channel 5 operates as TCU2, the others operate as TCU1.
+    - On newest SoCs (JZ4750 and above), channels 1-2 operate as TCU2, the
+      others operate as TCU1.
+
+- Each channel can generate an interrupt. Some channels share an interrupt
+  line, some don't, and this changes between SoC versions:
+
+    - on older SoCs (JZ4740 and below), channel 0 and channel 1 have their
+      own interrupt line; channels 2-7 share the last interrupt line.
+    - On JZ4725B, channel 0 has its own interrupt; channels 1-5 share one
+      interrupt line; the OST uses the last interrupt line.
+    - on newer SoCs (JZ4750 and above), channel 5 has its own interrupt;
+      channels 0-4 and (if eight channels) 6-7 all share one interrupt line;
+      the OST uses the last interrupt line.
+
+Implementation
+==============
+
+The functionalities of the TCU hardware are spread across multiple drivers:
+
+===========  =====
+clocks       drivers/clk/ingenic/tcu.c
+interrupts   drivers/irqchip/irq-ingenic-tcu.c
+timers       drivers/clocksource/ingenic-timer.c
+OST          drivers/clocksource/ingenic-ost.c
+PWM          drivers/pwm/pwm-jz4740.c
+watchdog     drivers/watchdog/jz4740_wdt.c
+===========  =====
+
+Because various functionalities of the TCU that belong to different drivers
+and frameworks can be controlled from the same registers, all of these
+drivers access their registers through the same regmap.
+
+For more information regarding the devicetree bindings of the TCU drivers,
+have a look at Documentation/devicetree/bindings/timer/ingenic,tcu.yaml.