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Gautham R. Shenoy dfd718a2ed powerpc/rtas: Fix a potential race between CPU-Offline & Migration 
Live Partition Migrations require all the present CPUs to execute the
H_JOIN call, and hence rtas_ibm_suspend_me() onlines any offline CPUs
before initiating the migration for this purpose.

The commit 85a88cabad
("powerpc/pseries: Disable CPU hotplug across migrations")
disables any CPU-hotplug operations once all the offline CPUs are
brought online to prevent any further state change. Once the
CPU-Hotplug operation is disabled, the code assumes that all the CPUs
are online.

However, there is a minor window in rtas_ibm_suspend_me() between
onlining the offline CPUs and disabling CPU-Hotplug when a concurrent
CPU-offline operations initiated by the userspace can succeed thereby
nullifying the the aformentioned assumption. In this unlikely case
these offlined CPUs will not call H_JOIN, resulting in a system hang.

Fix this by verifying that all the present CPUs are actually online
after CPU-Hotplug has been disabled, failing which we restore the
state of the offline CPUs in rtas_ibm_suspend_me() and return an
-EBUSY.

Cc: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Cc: Tyrel Datwyler <tyreld@linux.vnet.ibm.com>
Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Reviewed-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
2018-10-13 22:21:25 +11:00
arch powerpc/rtas: Fix a potential race between CPU-Offline & Migration 2018-10-13 22:21:25 +11:00
block block: bfq: swap puts in bfqg_and_blkg_put 2018-09-06 11:32:58 -06:00
certs
crypto
Documentation powerpc: Wire up memtest 2018-10-03 16:12:47 +10:00
drivers powerpc/eeh: Cleanup eeh_pe_state_mark() 2018-10-13 22:21:25 +11:00
firmware
fs afs: Fix cell specification to permit an empty address list 2018-09-07 16:39:44 -07:00
include macintosh: Use common code to access RTC 2018-10-08 22:53:10 +11:00
init
ipc
kernel Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-09-09 06:55:27 -07:00
lib lib/xz: Put CRC32_POLY_LE in xz_private.h 2018-10-02 08:44:59 +10:00
LICENSES
mm for-linus-20180906 2018-09-06 14:01:15 -07:00
net
samples
scripts Kbuild fixes for v4.19 2018-09-09 05:42:11 -07:00
security - Fix for bad debug check when converting secids to secctx 2018-09-06 09:42:14 -07:00
sound
tools Merge branch 'fixes' into next 2018-10-09 16:51:05 +11:00
usr
virt KVM: Remove obsolete kvm_unmap_hva notifier backend 2018-09-07 15:06:02 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
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COPYING
CREDITS
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MAINTAINERS i2c: xiic: Record xilinx i2c with Zynq fragment 2018-09-07 13:04:45 +02:00
Makefile Linux 4.19-rc3 2018-09-09 17:26:43 -07:00
README

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.