NothingOSS/android_kernel_msm-6.1_nothing_sm7635
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions
Kernel Source and devicetree for NOTHING Phone(3a) and Phone(3a)Pro
1059602 commits 1 branch 0 tags 2.6 GiB
Find a file
Linus Torvalds e386dfc56f fget: clarify and improve __fget_files() implementation 
Commit 054aa8d439 ("fget: check that the fd still exists after getting
a ref to it") fixed a race with getting a reference to a file just as it
was being closed.  It was a fairly minimal patch, and I didn't think
re-checking the file pointer lookup would be a measurable overhead,
since it was all right there and cached.

But I was wrong, as pointed out by the kernel test robot.

The 'poll2' case of the will-it-scale.per_thread_ops benchmark regressed
quite noticeably.  Admittedly it seems to be a very artificial test:
doing "poll()" system calls on regular files in a very tight loop in
multiple threads.

That means that basically all the time is spent just looking up file
descriptors without ever doing anything useful with them (not that doing
'poll()' on a regular file is useful to begin with).  And as a result it
shows the extra "re-check fd" cost as a sore thumb.

Happily, the regression is fixable by just writing the code to loook up
the fd to be better and clearer.  There's still a cost to verify the
file pointer, but now it's basically in the noise even for that
benchmark that does nothing else - and the code is more understandable
and has better comments too.

[ Side note: this patch is also a classic case of one that looks very
  messy with the default greedy Myers diff - it's much more legible with
  either the patience of histogram diff algorithm ]

Link: https://lore.kernel.org/lkml/20211210053743.GA36420@xsang-OptiPlex-9020/
Link: https://lore.kernel.org/lkml/20211213083154.GA20853@linux.intel.com/
Reported-by: kernel test robot <oliver.sang@intel.com>
Tested-by: Carel Si <beibei.si@intel.com>
Cc: Jann Horn <jannh@google.com>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-12-13 10:55:30 -08:00
arch A single fix for the x86 scheduler topology: 2021-12-12 09:38:04 -08:00
block block-5.16-2021-12-10 2021-12-11 09:25:07 -08:00
certs certs: Add support for using elliptic curve keys for signing modules 2021-08-23 19:55:42 +03:00
crypto Update to zstd-1.4.10 2021-11-13 15:32:30 -08:00
Documentation Char/misc driver fixes for 5.16-rc5 2021-12-12 10:16:34 -08:00
drivers USB fixes for 5.16-rc5 2021-12-12 10:20:57 -08:00
fs fget: clarify and improve __fget_files() implementation 2021-12-13 10:55:30 -08:00
include Char/misc driver fixes for 5.16-rc5 2021-12-12 10:16:34 -08:00
init kbuild: Fix -Wimplicit-fallthrough=5 error for GCC 5.x and 6.x 2021-11-14 18:59:49 -08:00
ipc shm: extend forced shm destroy to support objects from several IPC nses 2021-11-20 10:35:54 -08:00
kernel Merge branch 'akpm' (patches from Andrew) 2021-12-11 08:46:52 -08:00
lib Merge https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf 2021-12-08 16:06:44 -08:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm Merge branch 'for-5.16-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/dennis/percpu 2021-12-11 16:14:17 -08:00
net net/sched: fq_pie: prevent dismantle issue 2021-12-09 08:01:00 -08:00
samples ftrace/samples: Add module to test multi direct modify interface 2021-12-09 13:02:44 -05:00
scripts Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/hid/hid 2021-11-24 09:44:13 -08:00
security selinux: fix NULL-pointer dereference when hashtab allocation fails 2021-11-19 16:11:39 -05:00
sound sound fixes for 5.16-rc5 2021-12-10 11:43:00 -08:00
tools perf tools fixes for v5.16: 3rd batch 2021-12-11 13:28:02 -08:00
usr initramfs: Check timestamp to prevent broken cpio archive 2021-10-24 13:48:40 +09:00
virt KVM: downgrade two BUG_ONs to WARN_ON_ONCE 2021-11-26 06:43:28 -05:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +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 .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: update email address for Guo Ren 2021-12-10 17:10:55 -08:00
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 Char/misc driver fixes for 5.16-rc5 2021-12-12 10:16:34 -08:00
Makefile Linux 5.16-rc5 2021-12-12 14:53:01 -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.