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Oleg Nesterov 6d029c25b7 selftests/timers/posix_timers: Reimplement check_timer_distribution() 
check_timer_distribution() runs ten threads in a busy loop and tries to
test that the kernel distributes a process posix CPU timer signal to every
thread over time.

There is not guarantee that this is true even after commit bcb7ee7902
("posix-timers: Prefer delivery of signals to the current thread") because
that commit only avoids waking up the sleeping process leader thread, but
that has nothing to do with the actual signal delivery.

As the signal is process wide the first thread which observes sigpending
and wins the race to lock sighand will deliver the signal. Testing shows
that this hangs on a regular base because some threads never win the race.

The comment "This primarily tests that the kernel does not favour any one."
is wrong. The kernel does favour a thread which hits the timer interrupt
when CLOCK_PROCESS_CPUTIME_ID expires.

Rewrite the test so it only checks that the group leader sleeping in join()
never receives SIGALRM and the thread which burns CPU cycles receives all
signals.

In older kernels which do not have commit bcb7ee7902 ("posix-timers:
Prefer delivery of signals to the current thread") the test-case fails
immediately, the very 1st tick wakes the leader up. Otherwise it quickly
succeeds after 100 ticks.

CI testing wants to use newer selftest versions on stable kernels. In this
case the test is guaranteed to fail.

So check in the failure case whether the kernel version is less than v6.3
and skip the test result in that case.

[ tglx: Massaged change log, renamed the version check helper ]

Fixes: e797203fb3 ("selftests/timers/posix_timers: Test delivery of signals across threads")
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240409133802.GD29396@redhat.com
 		2024-04-09 17:48:19 +02:00
Documentation Devicetree fixes for v6.9, part 1: 2024-04-05 14:07:22 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
arch Miscellaneous x86 fixes: 2024-04-07 09:33:21 -07:00
block block-6.9-20240405 2024-04-05 17:04:11 -07:00
certs This update includes the following changes: 2023-11-02 16:15:30 -10:00
crypto This push fixes a regression that broke iwd as well as a divide by 2024-03-25 10:48:23 -07:00
drivers Miscellaneous x86 fixes: 2024-04-07 09:33:21 -07:00
fs nfsd-6.9 fixes: 2024-04-06 09:37:50 -07:00
include irqflags: Explicitly ignore lockdep_hrtimer_exit() argument 2024-04-08 16:34:18 +02:00
init init: open output files from cpio unpacking with O_LARGEFILE 2024-04-05 11:21:30 -07:00
io_uring io_uring/kbuf: hold io_buffer_list reference over mmap 2024-04-02 19:03:27 -06:00
ipc sysctl changes for v6.9-rc1 2024-03-18 14:59:13 -07:00
kernel Fix various timer bugs: 2024-04-07 09:20:50 -07:00
lib stackdepot: rename pool_index to pool_index_plus_1 2024-04-05 11:21:31 -07:00
mm x86/mm/pat: fix VM_PAT handling in COW mappings 2024-04-05 11:21:31 -07:00
net nfsd-6.9 fixes: 2024-04-06 09:37:50 -07:00
rust Kbuild updates for v6.9 2024-03-21 14:41:00 -07:00
samples Tracing updates for 6.9: 2024-03-18 15:11:44 -07:00
scripts Four small documentation fixes. 2024-04-02 12:44:09 -07:00
security security: Place security_path_post_mknod() where the original IMA call was 2024-04-03 10:21:32 -07:00
sound ASoC: Fixes for v6.9 2024-04-05 08:48:12 +02:00
tools selftests/timers/posix_timers: Reimplement check_timer_distribution() 2024-04-09 17:48:19 +02:00
usr Kbuild updates for v6.8 2024-01-18 17:57:07 -08:00
virt KVM Xen and pfncache changes for 6.9: 2024-03-11 10:42:55 -04:00
.clang-format clang-format: Update with v6.7-rc4's `for_each` macro list 2023-12-08 23:54:38 +01:00
.cocciconfig
…
.editorconfig Add .editorconfig file for basic formatting 2023-12-28 16:22:47 +09:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: create a list of all built DTB files 2024-02-19 18:20:39 +09:00
.mailmap MAINTAINERS: change vmware.com addresses to broadcom.com 2024-04-05 11:21:31 -07:00
.rustfmt.toml rust: add `.rustfmt.toml` 2022-09-28 09:02:20 +02:00
COPYING
…
CREDITS Not a ton of stuff happening in the clk framework in this pull request. We got 2024-03-15 11:48:01 -07:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig
…
MAINTAINERS Devicetree fixes for v6.9, part 1: 2024-04-05 14:07:22 -07:00
Makefile Linux 6.9-rc3 2024-04-07 13:22:46 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -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 reStructuredText 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.