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, 135 insertions, 0 deletions

diff --git a/Documentation/i2c/fault-codes.rst b/Documentation/i2c/fault-codes.rst
new file mode 100644
index 000000000..b0864d126
--- /dev/null
+++ b/Documentation/i2c/fault-codes.rst
@@ -0,0 +1,135 @@
+=====================
+I2C/SMBUS Fault Codes
+=====================
+
+This is a summary of the most important conventions for use of fault
+codes in the I2C/SMBus stack.
+
+
+A "Fault" is not always an "Error"
+----------------------------------
+Not all fault reports imply errors; "page faults" should be a familiar
+example.  Software often retries idempotent operations after transient
+faults.  There may be fancier recovery schemes that are appropriate in
+some cases, such as re-initializing (and maybe resetting).  After such
+recovery, triggered by a fault report, there is no error.
+
+In a similar way, sometimes a "fault" code just reports one defined
+result for an operation ... it doesn't indicate that anything is wrong
+at all, just that the outcome wasn't on the "golden path".
+
+In short, your I2C driver code may need to know these codes in order
+to respond correctly.  Other code may need to rely on YOUR code reporting
+the right fault code, so that it can (in turn) behave correctly.
+
+
+I2C and SMBus fault codes
+-------------------------
+These are returned as negative numbers from most calls, with zero or
+some positive number indicating a non-fault return.  The specific
+numbers associated with these symbols differ between architectures,
+though most Linux systems use <asm-generic/errno*.h> numbering.
+
+Note that the descriptions here are not exhaustive.  There are other
+codes that may be returned, and other cases where these codes should
+be returned.  However, drivers should not return other codes for these
+cases (unless the hardware doesn't provide unique fault reports).
+
+Also, codes returned by adapter probe methods follow rules which are
+specific to their host bus (such as PCI, or the platform bus).
+
+
+EAFNOSUPPORT
+	Returned by I2C adapters not supporting 10 bit addresses when
+	they are requested to use such an address.
+
+EAGAIN
+	Returned by I2C adapters when they lose arbitration in master
+	transmit mode:  some other master was transmitting different
+	data at the same time.
+
+	Also returned when trying to invoke an I2C operation in an
+	atomic context, when some task is already using that I2C bus
+	to execute some other operation.
+
+EBADMSG
+	Returned by SMBus logic when an invalid Packet Error Code byte
+	is received.  This code is a CRC covering all bytes in the
+	transaction, and is sent before the terminating STOP.  This
+	fault is only reported on read transactions; the SMBus slave
+	may have a way to report PEC mismatches on writes from the
+	host.  Note that even if PECs are in use, you should not rely
+	on these as the only way to detect incorrect data transfers.
+
+EBUSY
+	Returned by SMBus adapters when the bus was busy for longer
+	than allowed.  This usually indicates some device (maybe the
+	SMBus adapter) needs some fault recovery (such as resetting),
+	or that the reset was attempted but failed.
+
+EINVAL
+	This rather vague error means an invalid parameter has been
+	detected before any I/O operation was started.  Use a more
+	specific fault code when you can.
+
+EIO
+	This rather vague error means something went wrong when
+	performing an I/O operation.  Use a more specific fault
+	code when you can.
+
+ENODEV
+	Returned by driver probe() methods.  This is a bit more
+	specific than ENXIO, implying the problem isn't with the
+	address, but with the device found there.  Driver probes
+	may verify the device returns *correct* responses, and
+	return this as appropriate.  (The driver core will warn
+	about probe faults other than ENXIO and ENODEV.)
+
+ENOMEM
+	Returned by any component that can't allocate memory when
+	it needs to do so.
+
+ENXIO
+	Returned by I2C adapters to indicate that the address phase
+	of a transfer didn't get an ACK.  While it might just mean
+	an I2C device was temporarily not responding, usually it
+	means there's nothing listening at that address.
+
+	Returned by driver probe() methods to indicate that they
+	found no device to bind to.  (ENODEV may also be used.)
+
+EOPNOTSUPP
+	Returned by an adapter when asked to perform an operation
+	that it doesn't, or can't, support.
+
+	For example, this would be returned when an adapter that
+	doesn't support SMBus block transfers is asked to execute
+	one.  In that case, the driver making that request should
+	have verified that functionality was supported before it
+	made that block transfer request.
+
+	Similarly, if an I2C adapter can't execute all legal I2C
+	messages, it should return this when asked to perform a
+	transaction it can't.  (These limitations can't be seen in
+	the adapter's functionality mask, since the assumption is
+	that if an adapter supports I2C it supports all of I2C.)
+
+EPROTO
+	Returned when slave does not conform to the relevant I2C
+	or SMBus (or chip-specific) protocol specifications.  One
+	case is when the length of an SMBus block data response
+	(from the SMBus slave) is outside the range 1-32 bytes.
+
+ESHUTDOWN
+	Returned when a transfer was requested using an adapter
+	which is already suspended.
+
+ETIMEDOUT
+	This is returned by drivers when an operation took too much
+	time, and was aborted before it completed.
+
+	SMBus adapters may return it when an operation took more
+	time than allowed by the SMBus specification; for example,
+	when a slave stretches clocks too far.  I2C has no such
+	timeouts, but it's normal for I2C adapters to impose some
+	arbitrary limits (much longer than SMBus!) too.