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Prasad Sodagudi bd0f93a630 stop_machine: Atomically queue and wake stopper threads 
commit cfd355145c upstream.

When cpu_stop_queue_work() releases the lock for the stopper
thread that was queued into its wake queue, preemption is
enabled, which leads to the following deadlock:

CPU0                              CPU1
sched_setaffinity(0, ...)
__set_cpus_allowed_ptr()
stop_one_cpu(0, ...)              stop_two_cpus(0, 1, ...)
cpu_stop_queue_work(0, ...)       cpu_stop_queue_two_works(0, ..., 1, ...)

-grabs lock for migration/0-
                                  -spins with preemption disabled,
                                   waiting for migration/0's lock to be
                                   released-

-adds work items for migration/0
and queues migration/0 to its
wake_q-

-releases lock for migration/0
 and preemption is enabled-

-current thread is preempted,
and __set_cpus_allowed_ptr
has changed the thread's
cpu allowed mask to CPU1 only-

                                  -acquires migration/0 and migration/1's
                                   locks-

                                  -adds work for migration/0 but does not
                                   add migration/0 to wake_q, since it is
                                   already in a wake_q-

                                  -adds work for migration/1 and adds
                                   migration/1 to its wake_q-

                                  -releases migration/0 and migration/1's
                                   locks, wakes migration/1, and enables
                                   preemption-

                                  -since migration/1 is requested to run,
                                   migration/1 begins to run and waits on
                                   migration/0, but migration/0 will never
                                   be able to run, since the thread that
                                   can wake it is affine to CPU1-

Disable preemption in cpu_stop_queue_work() before queueing works for
stopper threads, and queueing the stopper thread in the wake queue, to
ensure that the operation of queueing the works and waking the stopper
threads is atomic.

Fixes: 0b26351b91 ("stop_machine, sched: Fix migrate_swap() vs. active_balance() deadlock")
Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: peterz@infradead.org
Cc: matt@codeblueprint.co.uk
Cc: bigeasy@linutronix.de
Cc: gregkh@linuxfoundation.org
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/1533329766-4856-1-git-send-email-isaacm@codeaurora.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Co-Developed-by: Isaac J. Manjarres <isaacm@codeaurora.org>
 		2018-09-05 09:26:36 +02:00
Documentation kbuild: verify that $DEPMOD is installed 2018-08-17 21:01:10 +02:00
arch s390/kvm: fix deadlock when killed by oom 2018-09-05 09:26:36 +02:00
block block: sed-opal: Fix a couple off by one bugs 2018-08-24 13:09:03 +02:00
certs License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
crypto crypto: skcipher - fix crash flushing dcache in error path 2018-08-17 21:01:10 +02:00
drivers iommu/arm-smmu: Error out only if not enough context interrupts 2018-09-05 09:26:34 +02:00
firmware License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
fs Btrfs: fix btrfs_write_inode vs delayed iput deadlock 2018-09-05 09:26:34 +02:00
include printk/nmi: Prevent deadlock when accessing the main log buffer in NMI 2018-09-05 09:26:35 +02:00
init init: rename and re-order boot_cpu_state_init() 2018-08-15 18:12:48 +02:00
ipc ipc/sem.c: prevent queue.status tearing in semop 2018-09-05 09:26:30 +02:00
kernel stop_machine: Atomically queue and wake stopper threads 2018-09-05 09:26:36 +02:00
lib printk/nmi: Prevent deadlock when accessing the main log buffer in NMI 2018-09-05 09:26:35 +02:00
mm mm/memory.c: check return value of ioremap_prot 2018-09-05 09:26:33 +02:00
net bpf: use GFP_ATOMIC instead of GFP_KERNEL in bpf_parse_prog() 2018-09-05 09:26:30 +02:00
samples samples/bpf: Check the error of write() and read() 2018-08-24 13:09:12 +02:00
scripts kconfig: fix line numbers for if-entries in menu tree 2018-08-24 13:09:06 +02:00
security Smack: Mark inode instant in smack_task_to_inode 2018-08-24 13:09:04 +02:00
sound ALSA: seq: Fix UBSAN warning at SNDRV_SEQ_IOCTL_QUERY_NEXT_CLIENT ioctl 2018-08-24 13:09:05 +02:00
tools tools/power turbostat: Read extended processor family from CPUID 2018-09-05 09:26:30 +02:00
usr initramfs: fix initramfs rebuilds w/ compression after disabling 2017-11-03 07:39:19 -07:00
virt KVM: arm/arm64: Skip updating PTE entry if no change 2018-09-05 09:26:36 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: rpm-pkg: keep spec file until make mrproper 2018-02-13 10:19:46 +01:00
.mailmap .mailmap: Add Maciej W. Rozycki's Imagination e-mail address 2017-11-10 12:16:15 -08:00
COPYING [PATCH] update FSF address in COPYING 2005-09-10 10:06:29 -07:00
CREDITS MAINTAINERS: update TPM driver infrastructure changes 2017-11-09 17:58:40 -08:00
Kbuild License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS dt-bindings: Document mti,mips-cpc binding 2018-03-15 10:54:35 +01:00
Makefile Linux 4.14.67 2018-08-24 13:09:23 +02:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

README 

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

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.