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Nicholas Piggin e012c49998 powerpc/watchdog: help remote CPUs to flush NMI printk output
The printk layer at the moment does not seem to have a good way to force
flush printk messages that are created in NMI context, except in the
panic path.

NMI-context printk messages normally get to the console with irq_work,
but that won't help if the CPU is stuck with irqs disabled, as can be
the case for hard lockup watchdog messages.

The watchdog currently flushes the printk buffers after detecting a
lockup on remote CPUs, but they may not have processed their NMI IPI
yet by that stage, or they may have self-detected a lockup in which
case they won't go via this NMI IPI path.

Improve the situation by having NMI-context mark a flag if it called
printk, and have watchdog timer interrupts check if that flag was set
and try to flush if it was. Latency is not a big problem because we
were already stuck for a while, just need to try to make sure the
messages eventually make it out.

Depends-on: 5d5e4522a7 ("printk: restore flushing of NMI buffers on remote CPUs after NMI backtraces")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Laurent Dufour <ldufour@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211119113146.752759-6-npiggin@gmail.com
2021-11-29 23:08:43 +11:00
arch powerpc/watchdog: help remote CPUs to flush NMI printk output 2021-11-29 23:08:43 +11:00
block blk-mq: don't insert FUA request with data into scheduler queue 2021-11-19 06:28:18 -07:00
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 powerpc/xive: Add a kernel parameter for StoreEOI 2021-11-25 11:25:30 +11:00
drivers Pin control fixes for the v5.16 kernel series: 2021-11-20 10:59:03 -08:00
fs pstore/blk: Use "%lu" to format unsigned long 2021-11-21 09:44:19 -08:00
include Merge branch 'akpm' (patches from Andrew) 2021-11-20 13:17:24 -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 Tracing fixes: 2021-11-19 13:50:48 -08:00
lib kasan: test: silence intentional read overflow warnings 2021-11-20 10:35:54 -08:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm kmap_local: don't assume kmap PTEs are linear arrays in memory 2021-11-20 10:35:54 -08:00
net Networking fixes for 5.16-rc2, including fixes from bpf, mac80211. 2021-11-18 12:54:24 -08:00
samples s390 updates for 5.16-rc2 2021-11-20 10:55:50 -08:00
scripts coccinelle patches for 5.16-rc1 2021-11-13 10:45:17 -08:00
security net,lsm,selinux: revert the security_sctp_assoc_established() hook 2021-11-14 12:21:53 +00:00
sound sound fixes for 5.16-rc1 2021-11-12 12:17:30 -08:00
tools perf tools fixes for 5.16: 1st batch 2021-11-19 12:47:29 -08:00
usr initramfs: Check timestamp to prevent broken cpio archive 2021-10-24 13:48:40 +09:00
virt Merge branch 'kvm-5.16-fixes' into kvm-master 2021-11-18 02:11:57 -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 MAINTAINERS: update email address of Christian Borntraeger 2021-11-18 17:50:54 +01:00
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 s390 updates for 5.16-rc2 2021-11-20 10:55:50 -08:00
Makefile Linux 5.16-rc2 2021-11-21 13:47:39 -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.