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Waiman Long 00f3c5a3df locking/rwsem: Always release wait_lock before waking up tasks
With the use of wake_q, we can do task wakeups without holding the
wait_lock. There is one exception in the rwsem code, though. It is
when the writer in the slowpath detects that there are waiters ahead
but the rwsem is not held by a writer. This can lead to a long wait_lock
hold time especially when a large number of readers are to be woken up.

Remediate this situation by releasing the wait_lock before waking
up tasks and re-acquiring it afterward. The rwsem_try_write_lock()
function is also modified to read the rwsem count directly to avoid
stale count value.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: huang ying <huang.ying.caritas@gmail.com>
Link: https://lkml.kernel.org/r/20190520205918.22251-9-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2019-06-17 12:28:00 +02:00
arch x86/atomic: Fix smp_mb__{before,after}_atomic() 2019-06-17 12:09:59 +02:00
block
certs
crypto
Documentation x86/atomic: Fix smp_mb__{before,after}_atomic() 2019-06-17 12:09:59 +02:00
drivers locking/lockdep: Rename lockdep_assert_held_exclusive() -> lockdep_assert_held_write() 2019-06-17 12:09:24 +02:00
fs locking/lockdep: Rename lockdep_assert_held_exclusive() -> lockdep_assert_held_write() 2019-06-17 12:09:24 +02:00
include locking/rwsem: Always release wait_lock before waking up tasks 2019-06-17 12:28:00 +02:00
init Linux 5.2-rc5 2019-06-17 12:06:34 +02:00
ipc
kernel locking/rwsem: Always release wait_lock before waking up tasks 2019-06-17 12:28:00 +02:00
lib locking/rwsem: Make owner available even if !CONFIG_RWSEM_SPIN_ON_OWNER 2019-06-17 12:27:54 +02:00
LICENSES
mm Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-06-16 07:28:14 -10:00
net
samples
scripts scripts/decode_stacktrace.sh: prefix addr2line with $CROSS_COMPILE 2019-06-13 17:34:56 -10:00
security locking/lockdep: Rename lockdep_assert_held_exclusive() -> lockdep_assert_held_write() 2019-06-17 12:09:24 +02:00
sound sound fixes for 5.2-rc5 2019-06-14 05:37:06 -10:00
tools mm/devm_memremap_pages: fix final page put race 2019-06-13 17:34:56 -10:00
usr
virt
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS
Makefile Linux 5.2-rc5 2019-06-16 08:49:45 -10:00
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.