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Waiman Long d10e819d13 locking/rwsem: Allow slowpath writer to ignore handoff bit if not set by first waiter 
commit 6eebd5fb20 upstream.

With commit d257cc8cb8 ("locking/rwsem: Make handoff bit handling more
consistent"), the writer that sets the handoff bit can be interrupted
out without clearing the bit if the wait queue isn't empty. This disables
reader and writer optimistic lock spinning and stealing.

Now if a non-first writer in the queue is somehow woken up or a new
waiter enters the slowpath, it can't acquire the lock.  This is not the
case before commit d257cc8cb8 as the writer that set the handoff bit
will clear it when exiting out via the out_nolock path. This is less
efficient as the busy rwsem stays in an unlock state for a longer time.

In some cases, this new behavior may cause lockups as shown in [1] and
[2].

This patch allows a non-first writer to ignore the handoff bit if it
is not originally set or initiated by the first waiter. This patch is
shown to be effective in fixing the lockup problem reported in [1].

[1] https://lore.kernel.org/lkml/20220617134325.GC30825@techsingularity.net/
[2] https://lore.kernel.org/lkml/3f02975c-1a9d-be20-32cf-f1d8e3dfafcc@oracle.com/

Fixes: d257cc8cb8 ("locking/rwsem: Make handoff bit handling more consistent")
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: John Donnelly <john.p.donnelly@oracle.com>
Tested-by: Mel Gorman <mgorman@techsingularity.net>
Link: https://lore.kernel.org/r/20220622200419.778799-1-longman@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-08-03 12:03:56 +02:00
arch ARM: 9216/1: Fix MAX_DMA_ADDRESS overflow 2022-08-03 12:03:55 +02:00
block block: fix rq-qos breakage from skipping rq_qos_done_bio() 2022-07-12 16:34:57 +02:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto crypto: memneq - move into lib/ 2022-06-22 14:22:03 +02:00
Documentation docs/kernel-parameters: Update descriptions for "mitigations=" param with retbleed 2022-08-03 12:03:55 +02:00
drivers EDAC/ghes: Set the DIMM label unconditionally 2022-08-03 12:03:55 +02:00
fs fs: sendfile handles O_NONBLOCK of out_fd 2022-08-03 12:03:41 +02:00
include net: Fix data-races around sysctl_[rw]mem(_offset)?. 2022-08-03 12:03:51 +02:00
init Kconfig: Add option for asm goto w/ tied outputs to workaround clang-13 bug 2022-06-09 10:23:26 +02:00
ipc ipc/mqueue: use get_tree_nodev() in mqueue_get_tree() 2022-06-09 10:23:10 +02:00
kernel locking/rwsem: Allow slowpath writer to ignore handoff bit if not set by first waiter 2022-08-03 12:03:56 +02:00
lib ida: don't use BUG_ON() for debugging 2022-07-12 16:35:18 +02:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm page_alloc: fix invalid watermark check on a negative value 2022-08-03 12:03:55 +02:00
net sctp: leave the err path free in sctp_stream_init to sctp_stream_free 2022-08-03 12:03:54 +02:00
samples samples/landlock: Format with clang-format 2022-06-09 10:23:23 +02:00
scripts x86/extable: Rework the exception table mechanics 2022-07-29 17:25:25 +02:00
security lockdown: Fix kexec lockdown bypass with ima policy 2022-07-29 17:25:05 +02:00
sound ALSA: usb-audio: Add quirk for Fiero SC-01 (fw v1.0.0) 2022-07-21 21:24:41 +02:00
tools perf symbol: Correct address for bss symbols 2022-08-03 12:03:54 +02:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:27:15 +01:00
virt KVM: Don't null dereference ops->destroy 2022-07-29 17:25:24 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
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.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 .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
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 Input: goodix - add a goodix.h header file 2022-07-12 16:34:51 +02:00
Makefile Linux 5.15.58 2022-07-29 17:25:34 +02:00
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.