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Filename Latest commit message Latest commit date
Steven Rostedt (Google) f7578a3b7c ring-buffer: Fix resetting of shortest_full
[ Upstream commit 68282dd930ea38b068ce2c109d12405f40df3f93 ]

The "shortest_full" variable is used to keep track of the waiter that is
waiting for the smallest amount on the ring buffer before being woken up.
When a tasks waits on the ring buffer, it passes in a "full" value that is
a percentage. 0 means wake up on any data. 1-100 means wake up from 1% to
100% full buffer.

As all waiters are on the same wait queue, the wake up happens for the
waiter with the smallest percentage.

The problem is that the smallest_full on the cpu_buffer that stores the
smallest amount doesn't get reset when all the waiters are woken up. It
does get reset when the ring buffer is reset (echo > /sys/kernel/tracing/trace).

This means that tasks may be woken up more often then when they want to
be. Instead, have the shortest_full field get reset just before waking up
all the tasks. If the tasks wait again, they will update the shortest_full
before sleeping.

Also add locking around setting of shortest_full in the poll logic, and
change "work" to "rbwork" to match the variable name for rb_irq_work
structures that are used in other places.

Link: https://lore.kernel.org/linux-trace-kernel/20240308202431.948914369@goodmis.org

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linke li <lilinke99@qq.com>
Cc: Rabin Vincent <rabin@rab.in>
Fixes: 2c2b0a78b3 ("ring-buffer: Add percentage of ring buffer full to wake up reader")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Stable-dep-of: 8145f1c35fa6 ("ring-buffer: Fix full_waiters_pending in poll")
Signed-off-by: Sasha Levin <sashal@kernel.org>
2024-04-13 12:51:26 +02:00
arch powerpc/fsl: Fix mfpmr build errors with newer binutils 2024-04-13 12:51:24 +02:00
block block: sed-opal: handle empty atoms when parsing response 2024-03-26 18:22:12 -04:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:11:22 +02:00
crypto crypto: api - Disallow identical driver names 2024-02-23 08:24:48 +01:00
Documentation x86/cpu: Support AMD Automatic IBRS 2024-04-13 12:51:21 +02:00
drivers vfio/platform: Disable virqfds on cleanup 2024-04-13 12:51:26 +02:00
fs ext4: fix corruption during on-line resize 2024-04-13 12:51:26 +02:00
include firmware: meson_sm: Rework driver as a proper platform driver 2024-04-13 12:51:26 +02:00
init rootfs: Fix support for rootfstype= when root= is given 2024-01-25 14:34:30 -08:00
ipc ipc/sem: Fix dangling sem_array access in semtimedop race 2022-12-08 11:23:06 +01:00
kernel ring-buffer: Fix resetting of shortest_full 2024-04-13 12:51:26 +02:00
lib net: blackhole_dev: fix build warning for ethh set but not used 2024-03-26 18:22:15 -04:00
LICENSES
mm userfaultfd: fix mmap_changing checking in mfill_atomic_hugetlb 2024-03-01 13:13:33 +01:00
net netfilter: nf_tables: do not compare internal table flags on updates 2024-03-26 18:22:25 -04:00
samples media: rename VFL_TYPE_GRABBER to _VIDEO 2024-03-26 18:22:22 -04:00
scripts kbuild: Move -Wenum-{compare-conditional,enum-conversion} into W=1 2024-04-13 12:51:26 +02:00
security smack: Handle SMACK64TRANSMUTE in smack_inode_setsecurity() 2024-04-13 12:51:22 +02:00
sound ALSA: usb-audio: Stop parsing channels bits when all channels are found. 2024-03-26 18:22:23 -04:00
tools selftests/mqueue: Set timeout to 180 seconds 2024-04-13 12:51:23 +02:00
usr
virt KVM: Always flush async #PF workqueue when vCPU is being destroyed 2024-04-13 12:51:22 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS iio: stx104: Move to addac subdirectory 2023-08-30 16:27:12 +02:00
Makefile Linux 5.4.273 2024-03-26 18:23:12 -04:00
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.