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Filename Latest commit message Latest commit date
Stefan Haberland 2757fe1d8e s390/dasd: fix unusable device after safe offline processing
The safe offline processing needs, as well as the normal offline
processing, to be locked against multiple parallel executions. But it
should be able to be overtaken by a normal offline processing to make sure
that the device does not wait forever for outstanding I/O if the user
wants to.

Unfortunately the parallel processing of safe offline and normal offline
might lead to a race situation where both threads report successful
execution to the CIO layer which in turn tries to deregister the kobject
of the device twice. This leads to a

refcount_t: underflow; use-after-free.

error and the device is not able to be set online again afterwards without
a reboot.

Correct the locking of the safe offline processing by doing the following:
	- Use the cdev lock to secure all set and test operations to the
	  device flags.
	- Two safe offline processes are locked against each other using
	  the DASD_FLAG_SAFE_OFFLINE and DASD_FLAG_SAFE_OFFLINE_RUNNING
	  device flags.
	  The differentiation between offline triggered and offline running
	  is needed since the normal offline attribute is owned by CIO and
	  we have to pass over control in between.
	- The dasd_generic_set_offline process handles the offline
	  processing. It is locked against parallel execution using the
	  DASD_FLAG_OFFLINE.
	- Only a running safe offline should be able to be overtaken by a
	  single normal offline. This is ensured by clearing the
	  DASD_FLAG_SAFE_OFFLINE_RUNNING flag when a normal offline
	  overtakes. So this can only happen ones.
	- The safe offline just aborts in this case doing nothing and
	  the normal offline processing finishes as usual.

Signed-off-by: Stefan Haberland <sth@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2017-06-12 16:26:01 +02:00
arch s390: provide default ioremap and iounmap declaration 2017-06-12 16:26:00 +02:00
block Merge branch 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm 2017-05-12 15:43:10 -07:00
certs
crypto
Documentation mm, docs: update memory.stat description with workingset* entries 2017-05-12 15:57:16 -07:00
drivers s390/dasd: fix unusable device after safe offline processing 2017-06-12 16:26:01 +02:00
firmware
fs Merge branch 'for-next' of git://git.samba.org/sfrench/cifs-2.6 2017-05-15 15:27:02 -07:00
include Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-05-15 15:50:49 -07:00
init Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-05-10 10:30:46 -07:00
ipc
kernel Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-05-15 15:50:49 -07:00
lib dmaengine updates for 4.12-rc1 2017-05-09 15:40:28 -07:00
mm mm: vmscan: scan until it finds eligible pages 2017-05-12 15:57:16 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-05-15 15:50:49 -07:00
samples samples/bpf: run cleanup routines when receiving SIGTERM 2017-05-11 21:43:30 -04:00
scripts Kbuild UAPI header export updates for v4.12 2017-05-10 20:45:36 -07:00
security Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-05-09 09:12:53 -07:00
sound sound fixes for 4.12-rc1 2017-05-12 12:10:38 -07:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-05-15 15:50:49 -07:00
usr
virt Second round of KVM/ARM Changes for v4.12. 2017-05-09 12:51:49 +02:00
.cocciconfig
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.mailmap power supply and reset changes for the v4.12 series (part 2) 2017-05-12 12:02:21 -07:00
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MAINTAINERS Tigran has moved 2017-05-12 15:57:15 -07:00
Makefile Linux 4.12-rc1 2017-05-13 13:19:49 -07:00
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.