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, 307 insertions, 0 deletions

diff --git a/Documentation/networking/arcnet-hardware.rst b/Documentation/networking/arcnet-hardware.rst
new file mode 100644
index 000000000..37c016cee
--- /dev/null
+++ b/Documentation/networking/arcnet-hardware.rst
@@ -0,0 +1,307 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===============
+ARCnet Hardware
+===============
+
+:Author: Avery Pennarun <apenwarr@worldvisions.ca>
+
+.. note::
+
+   This file is a supplement to arcnet.rst.  Please read that for general
+   driver configuration help.
+
+Because so many people (myself included) seem to have obtained ARCnet cards
+without manuals, this file contains a quick introduction to ARCnet hardware
+and some cabling tips. If you have any other information, do not hesitate to
+:ref:`send an email to netdev <arcnet-netdev>`.
+
+
+Introduction to ARCnet
+======================
+
+ARCnet is a network type which works in a way similar to popular Ethernet
+networks but which is also different in some very important ways.
+
+First of all, you can get ARCnet cards in at least two speeds: 2.5 Mbps
+(slower than Ethernet) and 100 Mbps (faster than normal Ethernet).  In fact,
+there are others as well, but these are less common.  The different hardware
+types, as far as I'm aware, are not compatible and so you cannot wire a
+100 Mbps card to a 2.5 Mbps card, and so on.  From what I hear, my driver does
+work with 100 Mbps cards, but I haven't been able to verify this myself,
+since I only have the 2.5 Mbps variety.  It is probably not going to saturate
+your 100 Mbps card.  Stop complaining. :)
+
+You also cannot connect an ARCnet card to any kind of Ethernet card and
+expect it to work.
+
+There are two "types" of ARCnet - STAR topology and BUS topology.  This
+refers to how the cards are meant to be wired together.  According to most
+available documentation, you can only connect STAR cards to STAR cards and
+BUS cards to BUS cards.  That makes sense, right?  Well, it's not quite
+true; see below under "Cabling."
+
+Once you get past these little stumbling blocks, ARCnet is actually quite a
+well-designed standard.  It uses something called "modified token passing"
+which makes it completely incompatible with so-called "Token Ring" cards,
+but which makes transfers much more reliable than Ethernet does.  In fact,
+ARCnet will guarantee that a packet arrives safely at the destination, and
+even if it can't possibly be delivered properly (ie. because of a cable
+break, or because the destination computer does not exist) it will at least
+tell the sender about it.
+
+Because of the carefully defined action of the "token", it will always make
+a pass around the "ring" within a maximum length of time.  This makes it
+useful for realtime networks.
+
+In addition, all known ARCnet cards have an (almost) identical programming
+interface.  This means that with one ARCnet driver you can support any
+card, whereas with Ethernet each manufacturer uses what is sometimes a
+completely different programming interface, leading to a lot of different,
+sometimes very similar, Ethernet drivers.  Of course, always using the same
+programming interface also means that when high-performance hardware
+facilities like PCI bus mastering DMA appear, it's hard to take advantage of
+them.  Let's not go into that.
+
+One thing that makes ARCnet cards difficult to program for, however, is the
+limit on their packet sizes; standard ARCnet can only send packets that are
+up to 508 bytes in length.  This is smaller than the Internet "bare minimum"
+of 576 bytes, let alone the Ethernet MTU of 1500.  To compensate, an extra
+level of encapsulation is defined by RFC1201, which I call "packet
+splitting," that allows "virtual packets" to grow as large as 64K each,
+although they are generally kept down to the Ethernet-style 1500 bytes.
+
+For more information on ARCnet networks, visit the "ARCNET Resource Center"
+WWW page at:
+
+	https://www.arcnet.cc
+
+
+Cabling ARCnet Networks
+=======================
+
+This section was rewritten by
+
+	Vojtech Pavlik     <vojtech@suse.cz>
+
+using information from several people, including:
+
+	- Avery Pennraun     <apenwarr@worldvisions.ca>
+	- Stephen A. Wood    <saw@hallc1.cebaf.gov>
+	- John Paul Morrison <jmorriso@bogomips.ee.ubc.ca>
+	- Joachim Koenig     <jojo@repas.de>
+
+and Avery touched it up a bit, at Vojtech's request.
+
+ARCnet (the classic 2.5 Mbps version) can be connected by two different
+types of cabling: coax and twisted pair.  The other ARCnet-type networks
+(100 Mbps TCNS and 320 kbps - 32 Mbps ARCnet Plus) use different types of
+cabling (Type1, Fiber, C1, C4, C5).
+
+For a coax network, you "should" use 93 Ohm RG-62 cable.  But other cables
+also work fine, because ARCnet is a very stable network. I personally use 75
+Ohm TV antenna cable.
+
+Cards for coax cabling are shipped in two different variants: for BUS and
+STAR network topologies.  They are mostly the same.  The only difference
+lies in the hybrid chip installed.  BUS cards use high impedance output,
+while STAR use low impedance.  Low impedance card (STAR) is electrically
+equal to a high impedance one with a terminator installed.
+
+Usually, the ARCnet networks are built up from STAR cards and hubs.  There
+are two types of hubs - active and passive.  Passive hubs are small boxes
+with four BNC connectors containing four 47 Ohm resistors::
+
+	   |         | wires
+	   R         + junction
+	-R-+-R-      R 47 Ohm resistors
+	   R
+	   |
+
+The shielding is connected together.  Active hubs are much more complicated;
+they are powered and contain electronics to amplify the signal and send it
+to other segments of the net.  They usually have eight connectors.  Active
+hubs come in two variants - dumb and smart.  The dumb variant just
+amplifies, but the smart one decodes to digital and encodes back all packets
+coming through.  This is much better if you have several hubs in the net,
+since many dumb active hubs may worsen the signal quality.
+
+And now to the cabling.  What you can connect together:
+
+1. A card to a card.  This is the simplest way of creating a 2-computer
+   network.
+
+2. A card to a passive hub.  Remember that all unused connectors on the hub
+   must be properly terminated with 93 Ohm terminators (or something else if you
+   don't have the right ones), although the network may work without
+   terminators.
+
+3. A card to an active hub.  Here there is no need to terminate the unused
+   connectors except some kind of aesthetic feeling.  But, there may not be
+   more than eleven active hubs between any two computers.  That of course
+   doesn't limit the number of active hubs on the network.
+
+4. An active hub to another.
+
+5. An active hub to passive hub.
+
+Remember that you cannot connect two passive hubs together.  The power loss
+implied by such a connection is too high for the network to operate reliably.
+
+An example of a typical ARCnet network::
+
+	   R                     S - STAR type card
+    S------H--------A-------S    R - Terminator
+	   |        |            H - Hub
+	   |        |            A - Active hub
+	   |   S----H----S
+	   S        |
+		    |
+		    S
+
+The BUS topology is very similar to the one used by 10BASE2 Ethernet.  The only
+difference is in cable and terminators: they should be 93 Ohm. 10BASE2 Ethernet
+uses 50 Ohm impedance. You use T connectors to put the computers on a single
+line of cable, the bus. You have to put terminators at both ends of the
+cable. A typical BUS ARCnet network looks like::
+
+    RT----T------T------T------T------TR
+     B    B      B      B      B      B
+
+  B - BUS type card
+  R - Terminator
+  T - T connector
+
+But that is not all! The two types can be connected together.  According to
+the official documentation, the only way of connecting them is using an active
+hub::
+
+	 A------T------T------TR
+	 |      B      B      B
+     S---H---S
+	 |
+	 S
+
+The official docs also state that you can use STAR cards at the ends of a
+BUS network in place of a BUS card and a terminator::
+
+     S------T------T------S
+	    B      B
+
+But, according to my own experiments, you can simply hang a BUS type card
+anywhere in middle of a cable in a STAR topology network.  And more - you
+can use the bus card in place of any star card if you use a terminator. Then
+you can build very complicated networks fulfilling all your needs!  An
+example::
+
+				  S
+				  |
+	   RT------T-------T------H------S
+	    B      B       B      |
+				  |       R
+    S------A------T-------T-------A-------H------TR
+	   |      B       B       |       |      B
+	   |   S                 BT       |
+	   |   |                  |  S----A-----S
+    S------H---A----S             |       |
+	   |   |      S------T----H---S   |
+	   S   S             B    R       S
+
+A completely different cabling scheme is used with Twisted Pair cabling. Each
+of the TP cards has two RJ (phone-cord style) connectors.  The cards are
+then daisy-chained together using a cable connecting every two neighboring
+cards.  The ends are terminated with RJ 93 Ohm terminators which plug into
+the empty connectors of cards on the ends of the chain.  An example::
+
+	  ___________   ___________
+      _R_|_         _|_|_         _|_R_
+     |     |       |     |       |     |
+     |Card |       |Card |       |Card |
+     |_____|       |_____|       |_____|
+
+
+There are also hubs for the TP topology.  There is nothing difficult
+involved in using them; you just connect a TP chain to a hub on any end or
+even at both.  This way you can create almost any network configuration.
+The maximum of 11 hubs between any two computers on the net applies here as
+well.  An example::
+
+    RP-------P--------P--------H-----P------P-----PR
+			       |
+      RP-----H--------P--------H-----P------PR
+	     |                 |
+	     PR                PR
+
+    R - RJ Terminator
+    P - TP Card
+    H - TP Hub
+
+Like any network, ARCnet has a limited cable length.  These are the maximum
+cable lengths between two active ends (an active end being an active hub or
+a STAR card).
+
+		========== ======= ===========
+		RG-62       93 Ohm up to 650 m
+		RG-59/U     75 Ohm up to 457 m
+		RG-11/U     75 Ohm up to 533 m
+		IBM Type 1 150 Ohm up to 200 m
+		IBM Type 3 100 Ohm up to 100 m
+		========== ======= ===========
+
+The maximum length of all cables connected to a passive hub is limited to 65
+meters for RG-62 cabling; less for others.  You can see that using passive
+hubs in a large network is a bad idea. The maximum length of a single "BUS
+Trunk" is about 300 meters for RG-62. The maximum distance between the two
+most distant points of the net is limited to 3000 meters. The maximum length
+of a TP cable between two cards/hubs is 650 meters.
+
+
+Setting the Jumpers
+===================
+
+  - Every ARCnet card has its own "unique" network address from 0 to 255.
+    Unlike Ethernet, you can set this address yourself with a jumper or switch
+    (or on some cards, with special software).  Since it's only 8 bits, you can
+    only have 254 ARCnet cards on a network.  DON'T use 0 or 255, since these
+    are reserved (although neat stuff will probably happen if you DO use them).
+    By the way, if you haven't already guessed, don't set this the same as any
+    other ARCnet device on your network!
+
+  - There may be ETS1 and ETS2 settings.  These may or may not make a
+    difference on your card (many manuals call them "reserved"), but are
+    used to change the delays used when powering up a computer on the
+    network.  This is only necessary when wiring VERY long range ARCnet
+    networks, on the order of 4km or so; in any case, the only real
+    requirement here is that all cards on the network with ETS1 and ETS2
+    jumpers have them in the same position.  Chris Hindy <chrish@io.org>
+    sent in a chart with actual values for this:
+
+	======= ======= =============== ====================
+	ET1	ET2	Response Time	Reconfiguration Time
+	======= ======= =============== ====================
+	open	open	74.7us		840us
+	open	closed	283.4us		1680us
+	closed	open	561.8us		1680us
+	closed	closed	1118.6us	1680us
+	======= ======= =============== ====================
+
+    Make sure you set ETS1 and ETS2 to the SAME VALUE for all cards on your
+    network.
+
+LED Indicators
+==============
+
+Many cards have red and green LEDs, which have the following meanings:
+
+	=============== =============== =====================================
+	Green           Red             Status
+	=============== =============== =====================================
+	OFF             OFF             Power off
+	OFF             Short flashes   Cabling problems (broken cable or not
+					terminated)
+	OFF (short)     ON              Card init
+	ON              ON              Normal state - everything OK, nothing
+					happens
+	ON              Long flashes    Data transfer
+	ON              OFF             Never happens (maybe when wrong ID)
+	=============== =============== =====================================