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, 105 insertions, 0 deletions

diff --git a/Documentation/gpu/amdgpu/debugging.rst b/Documentation/gpu/amdgpu/debugging.rst
new file mode 100644
index 000000000..ac914d524
--- /dev/null
+++ b/Documentation/gpu/amdgpu/debugging.rst
@@ -0,0 +1,105 @@
+===============
+ GPU Debugging
+===============
+
+General Debugging Options
+=========================
+
+The DebugFS section provides documentation on a number files to aid in debugging
+issues on the GPU.
+
+
+GPUVM Debugging
+===============
+
+To aid in debugging GPU virtual memory related problems, the driver supports a
+number of options module parameters:
+
+`vm_fault_stop` - If non-0, halt the GPU memory controller on a GPU page fault.
+
+`vm_update_mode` - If non-0, use the CPU to update GPU page tables rather than
+the GPU.
+
+
+Decoding a GPUVM Page Fault
+===========================
+
+If you see a GPU page fault in the kernel log, you can decode it to figure
+out what is going wrong in your application.  A page fault in your kernel
+log may look something like this:
+
+::
+
+ [gfxhub0] no-retry page fault (src_id:0 ring:24 vmid:3 pasid:32777, for process glxinfo pid 2424 thread glxinfo:cs0 pid 2425)
+   in page starting at address 0x0000800102800000 from IH client 0x1b (UTCL2)
+ VM_L2_PROTECTION_FAULT_STATUS:0x00301030
+ 	Faulty UTCL2 client ID: TCP (0x8)
+ 	MORE_FAULTS: 0x0
+ 	WALKER_ERROR: 0x0
+ 	PERMISSION_FAULTS: 0x3
+ 	MAPPING_ERROR: 0x0
+ 	RW: 0x0
+
+First you have the memory hub, gfxhub and mmhub.  gfxhub is the memory
+hub used for graphics, compute, and sdma on some chips.  mmhub is the
+memory hub used for multi-media and sdma on some chips.
+
+Next you have the vmid and pasid.  If the vmid is 0, this fault was likely
+caused by the kernel driver or firmware.  If the vmid is non-0, it is generally
+a fault in a user application.  The pasid is used to link a vmid to a system
+process id.  If the process is active when the fault happens, the process
+information will be printed.
+
+The GPU virtual address that caused the fault comes next.
+
+The client ID indicates the GPU block that caused the fault.
+Some common client IDs:
+
+- CB/DB: The color/depth backend of the graphics pipe
+- CPF: Command Processor Frontend
+- CPC: Command Processor Compute
+- CPG: Command Processor Graphics
+- TCP/SQC/SQG: Shaders
+- SDMA: SDMA engines
+- VCN: Video encode/decode engines
+- JPEG: JPEG engines
+
+PERMISSION_FAULTS describe what faults were encountered:
+
+- bit 0: the PTE was not valid
+- bit 1: the PTE read bit was not set
+- bit 2: the PTE write bit was not set
+- bit 3: the PTE execute bit was not set
+
+Finally, RW, indicates whether the access was a read (0) or a write (1).
+
+In the example above, a shader (cliend id = TCP) generated a read (RW = 0x0) to
+an invalid page (PERMISSION_FAULTS = 0x3) at GPU virtual address
+0x0000800102800000.  The user can then inspect their shader code and resource
+descriptor state to determine what caused the GPU page fault.
+
+UMR
+===
+
+`umr <https://gitlab.freedesktop.org/tomstdenis/umr>`_ is a general purpose
+GPU debugging and diagnostics tool.  Please see the umr
+`documentation <https://umr.readthedocs.io/en/main/>`_ for more information
+about its capabilities.
+
+Debugging backlight brightness
+==============================
+Default backlight brightness is intended to be set via the policy advertised
+by the firmware.  Firmware will often provide different defaults for AC or DC.
+Furthermore, some userspace software will save backlight brightness during
+the previous boot and attempt to restore it.
+
+Some firmware also has support for a feature called "Custom Backlight Curves"
+where an input value for brightness is mapped along a linearly interpolated
+curve of brightness values that better match display characteristics.
+
+In the event of problems happening with backlight, there is a trace event
+that can be enabled at bootup to log every brightness change request.
+This can help isolate where the problem is. To enable the trace event add
+the following to the kernel command line:
+
+  tp_printk trace_event=amdgpu_dm:amdgpu_dm_brightness:mod:amdgpu trace_buf_size=1M