linux/arch/powerpc
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
..
boot powerpc/boot: Build boot wrapper with optimisations 2018-10-13 22:21:25 +11:00
configs powerpc/config: Enable CONFIG_PRINTK_TIME 2018-10-03 15:40:06 +10:00
crypto powerpc updates for 4.19 2018-08-17 11:32:50 -07:00
include powerpc: Detect the presence of big-cores via "ibm, thread-groups" 2018-10-13 22:21:25 +11:00
kernel powerpc/rtas: Fix a potential race between CPU-Offline & Migration 2018-10-13 22:21:25 +11:00
kvm PPC KVM fixes for 4.19 2018-09-04 21:12:46 +02:00
lib Merge branch 'fixes' into next 2018-10-09 16:51:05 +11:00
math-emu License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
mm powerpc/pseries/mobility: Extend start/stop topology update scope 2018-10-13 22:21:25 +11:00
net powerpc updates for 4.19 2018-08-17 11:32:50 -07:00
oprofile treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
perf powerpc/perf: Quiet IMC PMU registration message 2018-10-13 22:21:25 +11:00
platforms powerpc/pseries/mobility: Extend start/stop topology update scope 2018-10-13 22:21:25 +11:00
purgatory powerpc updates for 4.19 2018-08-17 11:32:50 -07:00
sysdev powerpc: remove redundant 'default n' from Kconfig-s 2018-10-13 22:21:25 +11:00
tools powerpc: Add a checkpatch wrapper with our preferred settings 2018-08-07 21:49:25 +10:00
xmon powerpc/xmon: Show the stack protector canary in xmon 2018-10-13 22:21:25 +11:00
Kconfig powerpc: Fix stackprotector detection for non-glibc toolchains 2018-10-13 22:21:25 +11:00
Kconfig.debug powerpc: remove redundant 'default n' from Kconfig-s 2018-10-13 22:21:25 +11:00
Makefile powerpc/Makefile: Fix PPC_BOOK3S_64 ASFLAGS 2018-10-13 22:21:25 +11:00
Makefile.postlink License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00