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wuqiang 3b7ddab8a1 kprobes: kretprobe events missing on 2-core KVM guest
Default value of maxactive is set as num_possible_cpus() for nonpreemptable
systems. For a 2-core system, only 2 kretprobe instances would be allocated
in default, then these 2 instances for execve kretprobe are very likely to
be used up with a pipelined command.

Here's the testcase: a shell script was added to crontab, and the content
of the script is:

  #!/bin/sh
  do_something_magic `tr -dc a-z < /dev/urandom | head -c 10`

cron will trigger a series of program executions (4 times every hour). Then
events loss would be noticed normally after 3-4 hours of testings.

The issue is caused by a burst of series of execve requests. The best number
of kretprobe instances could be different case by case, and should be user's
duty to determine, but num_possible_cpus() as the default value is inadequate
especially for systems with small number of cpus.

This patch enables the logic for preemption as default, thus increases the
minimum of maxactive to 10 for nonpreemptable systems.

Link: https://lore.kernel.org/all/20221110081502.492289-1-wuqiang.matt@bytedance.com/

Signed-off-by: wuqiang <wuqiang.matt@bytedance.com>
Reviewed-by: Solar Designer <solar@openwall.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
2022-12-15 08:48:40 +09:00
arch - fix jump label branch range check 2022-11-13 07:57:33 -08:00
block block-6.1-2022-11-11 2022-11-11 14:08:30 -08:00
certs certs: make system keyring depend on built-in x509 parser 2022-09-24 04:31:18 +09:00
crypto treewide: use get_random_bytes() when possible 2022-10-11 17:42:58 -06:00
Documentation kprobes: kretprobe events missing on 2-core KVM guest 2022-12-15 08:48:40 +09:00
drivers Third batch of EFI fixes for v6.1 2022-11-13 07:52:22 -08:00
fs 22 hotfixes. 8 are cc:stable and the remainder address issues which were 2022-11-11 17:18:42 -08:00
include tracing/ring-buffer: Have polling block on watermark 2022-11-16 17:13:04 -05:00
init init: Kconfig: fix spelling mistake "satify" -> "satisfy" 2022-10-20 21:27:22 -07:00
io_uring io_uring/poll: lockdep annote io_poll_req_insert_locked 2022-11-11 09:59:27 -07:00
ipc ipc/msg.c: fix percpu_counter use after free 2022-10-28 13:37:22 -07:00
kernel kprobes: kretprobe events missing on 2-core KVM guest 2022-12-15 08:48:40 +09:00
lib test_kprobes: Fix implicit declaration error of test_kprobes 2022-11-24 00:43:15 +09:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm 22 hotfixes. 8 are cc:stable and the remainder address issues which were 2022-11-11 17:18:42 -08:00
net mctp: Fix an error handling path in mctp_init() 2022-11-09 19:26:08 -08:00
rust Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
samples VFIO updates for v6.1-rc1 2022-10-12 14:46:48 -07:00
scripts s390 updates for 6.1-rc5 2022-11-11 11:49:20 -08:00
security lsm/stable-6.1 PR 20221031 2022-10-31 12:09:42 -07:00
sound ALSA: memalloc: Try dma_alloc_noncontiguous() at first 2022-11-12 09:48:51 +01:00
tools 22 hotfixes. 8 are cc:stable and the remainder address issues which were 2022-11-11 17:18:42 -08:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt Merge tag 'kvmarm-fixes-6.1-3' of git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEAD 2022-11-06 03:30:49 -05:00
.clang-format PCI/DOE: Add DOE mailbox support functions 2022-07-19 15:38:04 -07:00
.cocciconfig
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
.mailmap mailmap: update email for Qais Yousef 2022-10-20 21:27:21 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Vivien to CREDITS 2022-11-10 13:53:53 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS hyperv-fixes for v6.1-rc5 2022-11-11 09:24:03 -08:00
Makefile Linux 6.1-rc5 2022-11-13 13:12:55 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.