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Beata Michalska 606a5d4227 opp: Don't drop extra references to OPPs accidentally 
We are required to call dev_pm_opp_put() from outside of the
opp_table->lock as debugfs removal needs to happen lock-less to avoid
circular dependency issues.

commit cf1fac943c ("opp: Reduce the size of critical section in
_opp_kref_release()") tried to fix that introducing a new routine
_opp_get_next() which keeps returning OPPs that can be freed by the
callers and this routine shall be called without holding the
opp_table->lock.

Though the commit overlooked the fact that the OPPs can be referenced by
other users as well and this routine will end up dropping references
which were taken by other users and hence freeing the OPPs prematurely.

In effect, other users of the OPPs will end up having invalid pointers
at hand. We didn't see any crash reports earlier as the exact situation
never happened, though it is certainly possible.

We need a way to mark which OPPs are no longer referenced by the OPP
core, so we don't drop extra references to them accidentally.

This commit adds another OPP flag, "removed", which is used to track
this. And now we should never end up dropping extra references to the
OPPs.

Cc: v5.11+ <stable@vger.kernel.org> # v5.11+
Fixes: cf1fac943c ("opp: Reduce the size of critical section in _opp_kref_release()")
Signed-off-by: Beata Michalska <beata.michalska@arm.com>
[ Viresh: Almost rewrote entire patch, added new "removed" field,
	  rewrote commit log and added the correct Fixes tag. ]
Co-developed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
2021-03-12 09:26:52 +05:30
arch * Doc fixes 2021-03-04 11:26:17 -08:00
block block/bfq: update comments and default value in docs for fifo_expire 2021-03-02 11:25:38 -07:00
certs certs: Replace K{U,G}IDT_INIT() with GLOBAL_ROOT_{U,G}ID 2021-01-21 16:16:10 +00:00
crypto Keyrings miscellany 2021-02-23 16:09:23 -08:00
Documentation block-5.12-2021-03-05 2021-03-05 12:59:37 -08:00
drivers opp: Don't drop extra references to OPPs accidentally 2021-03-12 09:26:52 +05:30
fs pstore fixes for v5.12-rc2 2021-03-05 17:21:25 -08:00
include block-5.12-2021-03-05 2021-03-05 12:59:37 -08:00
init kbuild: fix UNUSED_KSYMS_WHITELIST for Clang LTO 2021-02-28 15:19:21 +09:00
ipc fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
kernel io_uring-5.12-2021-03-05 2021-03-05 12:44:43 -08:00
lib Merge branch 'kmap-conversion-for-5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux 2021-03-01 11:24:18 -08:00
LICENSES LICENSES: Add the CC-BY-4.0 license 2020-12-08 10:33:27 -07:00
mm swap: fix swapfile read/write offset 2021-03-02 17:25:46 -07:00
net io_uring-worker.v3-2021-02-25 2021-02-27 08:29:02 -08:00
samples treewide: Miguel has moved 2021-02-26 09:41:03 -08:00
scripts gcc-plugins fixes for v5.12-rc2 2021-03-05 17:23:03 -08:00
security Keyrings miscellany 2021-02-23 16:09:23 -08:00
sound ALSA: hda/realtek: Apply dual codec quirks for MSI Godlike X570 board 2021-03-03 15:25:03 +01:00
tools * Doc fixes 2021-03-04 11:26:17 -08:00
usr Kbuild updates for v5.12 2021-02-25 10:17:31 -08:00
virt KVM: x86/mmu: Consider the hva in mmu_notifier retry 2021-02-22 13:16:53 -05:00
.clang-format cxl for 5.12 2021-02-24 09:38:36 -08:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.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 clang-lto series for v5.12-rc1 2021-02-23 09:28:51 -08:00
.mailmap treewide: Miguel has moved 2021-02-26 09:41:03 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS treewide: Miguel has moved 2021-02-26 09:41:03 -08:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS RISC-V Patches for the 5.12 Merge Window 2021-02-26 10:28:35 -08:00
Makefile Linux 5.12-rc2 2021-03-05 17:33:41 -08:00
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.