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Brendan Higgins 7589238a8c Revert "software node: Simplify software_node_release() function" 
This reverts commit 3df85a1ae5.

The reverted commit says "It's possible to release the node ID
immediately when fwnode_remove_software_node() is called, no need to
wait for software_node_release() with that." However, releasing the node
ID before waiting for software_node_release() to be called causes the
node ID to be released before the kobject and the underlying sysfs
entry; this means there is a period of time where a sysfs entry exists
that is associated with an unallocated node ID.

Once consequence of this is that there is a race condition where it is
possible to call fwnode_create_software_node() with no parent node
specified (NULL) and have it fail with -EEXIST because the node ID that
was assigned is still associated with a stale sysfs entry that hasn't
been cleaned up yet.

Although it is difficult to reproduce this race condition under normal
conditions, it can be deterministically reproduced with the following
minconfig on UML:

CONFIG_KUNIT_DRIVER_PE_TEST=y
CONFIG_DEBUG_KERNEL=y
CONFIG_DEBUG_OBJECTS=y
CONFIG_DEBUG_OBJECTS_TIMERS=y
CONFIG_DEBUG_KOBJECT_RELEASE=y
CONFIG_KUNIT=y

Running the tests with this configuration causes the following failure:

<snip>
kobject: 'node0' ((____ptrval____)): kobject_release, parent (____ptrval____) (delayed 400)
	ok 1 - pe_test_uints
sysfs: cannot create duplicate filename '/kernel/software_nodes/node0'
CPU: 0 PID: 28 Comm: kunit_try_catch Not tainted 5.6.0-rc3-next-20200227 #14
<snip>
kobject_add_internal failed for node0 with -EEXIST, don't try to register things with the same name in the same directory.
kobject: 'node0' ((____ptrval____)): kobject_release, parent (____ptrval____) (delayed 100)
	# pe_test_uint_arrays: ASSERTION FAILED at drivers/base/test/property-entry-test.c:123
	Expected node is not error, but is: -17
	not ok 2 - pe_test_uint_arrays
<snip>

Reported-by: Heidi Fahim <heidifahim@google.com>
Signed-off-by: Brendan Higgins <brendanhiggins@google.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Cc: 5.3+ <stable@vger.kernel.org> # 5.3+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2020-03-04 22:31:44 +01:00
arch More bugfixes, including a few remaining "make W=1" issues such 2020-03-01 15:16:35 -06:00
block blk-mq: Remove some unused function arguments 2020-02-26 10:34:41 -07:00
certs certs: Add wrapper function to check blacklisted binary hash 2019-11-12 12:25:50 +11:00
crypto Merge branch 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity 2020-02-20 15:15:16 -08:00
Documentation ACPI fixes for 5.6-rc4 2020-02-28 09:02:18 -08:00
drivers Revert "software node: Simplify software_node_release() function" 2020-03-04 22:31:44 +01:00
fs Two more bug fixes (including a regression) for 5.6 2020-03-01 16:35:08 -06:00
include More bugfixes, including a few remaining "make W=1" issues such 2020-03-01 15:16:35 -06:00
init Tracing updates: 2020-02-26 10:34:42 -08:00
ipc Revert "ipc,sem: remove uneeded sem_undo_list lock usage in exit_sem()" 2020-02-21 11:22:15 -08:00
kernel block-5.6-2020-02-28 2020-02-28 11:43:30 -08:00
lib Tracing updates: 2020-02-26 10:34:42 -08:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-02-24 11:32:15 -08:00
net vsock: fix potential deadlock in transport->release() 2020-02-27 12:03:56 -08:00
samples Kbuild updates for v5.6 (2nd) 2020-02-09 16:05:50 -08:00
scripts kbuild: remove unneeded semicolon at the end of cmd_dtb_check 2020-02-27 02:24:34 +09:00
security Merge branch 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity 2020-02-20 15:15:16 -08:00
sound ASoC: Fixes for v5.6 2020-02-18 13:33:39 +01:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-02-27 16:34:41 -08:00
usr Kbuild updates for v5.6 (2nd) 2020-02-09 16:05:50 -08:00
virt KVM/arm fixes for 5.6, take #1 2020-02-28 11:50:06 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore selftest/lkdtm: Don't pollute 'git status' 2020-02-20 08:55:06 -07:00
.mailmap A handful of small documentation fixes that wandered in. 2020-02-07 13:03:10 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Hand MIPS over to Thomas 2020-02-24 22:43:18 -08:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS pci-v5.6-fixes-2 2020-02-28 11:51:53 -08:00
Makefile Linux 5.6-rc4 2020-03-01 16:38:46 -06:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.