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Filename Latest commit message Latest commit date
Nicholas Piggin de6e5d3841 powerpc: smp_send_stop do not offline stopped CPUs
Marking CPUs stopped by smp_send_stop as offline can cause warnings
due to cross-CPU wakeups. This trace was noticed on a busy system
running a sysrq+c crash test, after the injected crash:

WARNING: CPU: 51 PID: 1546 at kernel/sched/core.c:1179 set_task_cpu+0x22c/0x240
CPU: 51 PID: 1546 Comm: kworker/u352:1 Tainted: G      D
Workqueue: mlx5e mlx5e_update_stats_work [mlx5_core]
[...]
NIP [c00000000017c21c] set_task_cpu+0x22c/0x240
LR [c00000000017d580] try_to_wake_up+0x230/0x720
Call Trace:
[c000000001017700] runqueues+0x0/0xb00 (unreliable)
[c00000000017d580] try_to_wake_up+0x230/0x720
[c00000000015a214] insert_work+0x104/0x140
[c00000000015adb0] __queue_work+0x230/0x690
[c000003fc5007910] [c00000000015b26c] queue_work_on+0x5c/0x90
[c0080000135fc8f8] mlx5_cmd_exec+0x538/0xcb0 [mlx5_core]
[c008000013608fd0] mlx5_core_access_reg+0x140/0x1d0 [mlx5_core]
[c00800001362777c] mlx5e_update_pport_counters.constprop.59+0x6c/0x90 [mlx5_core]
[c008000013628868] mlx5e_update_ndo_stats+0x28/0x90 [mlx5_core]
[c008000013625558] mlx5e_update_stats_work+0x68/0xb0 [mlx5_core]
[c00000000015bcec] process_one_work+0x1bc/0x5f0
[c00000000015ecac] worker_thread+0xac/0x6b0
[c000000000168338] kthread+0x168/0x1b0
[c00000000000b628] ret_from_kernel_thread+0x5c/0xb4

This happens because firstly the CPU is not really offline in the
usual sense, processes and interrupts have not been migrated away.
Secondly smp_send_stop does not happen atomically on all CPUs, so
one CPU can have marked itself offline, while another CPU is still
running processes or interrupts which can affect the first CPU.

Fix this by just not marking the CPU as offline. It's more like
frozen in time, so offline does not really reflect its state properly
anyway. There should be nothing in the crash/panic path that walks
online CPUs and synchronously waits for them, so this change should
not introduce new hangs.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
2018-06-19 21:28:23 +10:00
arch powerpc: smp_send_stop do not offline stopped CPUs 2018-06-19 21:28:23 +10:00
block for-linus-20180616 2018-06-17 05:37:55 +09:00
certs docs: Fix some broken references 2018-06-15 18:10:01 -03:00
crypto docs: Fix some broken references 2018-06-15 18:10:01 -03:00
Documentation for-linus-20180616 2018-06-17 05:37:55 +09:00
drivers for-linus-20180616 2018-06-17 05:37:55 +09:00
firmware
fs Solve a series of broken links for files under Documentation: 2018-06-17 05:25:18 +09:00
include for-linus-20180616 2018-06-17 05:37:55 +09:00
init Kbuild updates for v4.18 (2nd) 2018-06-13 08:40:34 -07:00
ipc ipc: use new return type vm_fault_t 2018-06-15 07:55:25 +09:00
kernel Solve a series of broken links for files under Documentation: 2018-06-17 05:25:18 +09:00
lib docs: Fix some broken references 2018-06-15 18:10:01 -03:00
LICENSES
mm mm: fix oom_kill event handling 2018-06-15 07:55:25 +09:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-06-16 07:39:34 +09:00
samples VFIO updates for v4.18 2018-06-12 13:11:26 -07:00
scripts scripts/documentation-file-ref-check: check tools/*/Documentation 2018-06-15 18:10:01 -03:00
security docs: Fix some broken references 2018-06-15 18:10:01 -03:00
sound docs: Fix some broken references 2018-06-15 18:10:01 -03:00
tools Solve a series of broken links for files under Documentation: 2018-06-17 05:25:18 +09:00
usr
virt - Error path bug fix for overflow tests (Dan) 2018-06-12 18:28:00 -07:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig kconfig: add basic helper macros to scripts/Kconfig.include 2018-05-29 03:31:19 +09:00
MAINTAINERS Solve a series of broken links for files under Documentation: 2018-06-17 05:25:18 +09:00
Makefile Linux 4.18-rc1 2018-06-17 08:04:49 +09:00
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.
See Documentation/00-INDEX for a list of what is contained in each file.

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.