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Julian Wiedmann b6366b15a2 s390/qdio: don't retry EQBS after CCQ 96 
commit dae55b6fef upstream.

Immediate retry of EQBS after CCQ 96 means that we potentially misreport
the state of buffers inspected during the first EQBS call.

This occurs when
1. the first EQBS finds all inspected buffers still in the initial state
   set by the driver (ie INPUT EMPTY or OUTPUT PRIMED),
2. the EQBS terminates early with CCQ 96, and
3. by the time that the second EQBS comes around, the state of those
   previously inspected buffers has changed.

If the state reported by the second EQBS is 'driver-owned', all we know
is that the previous buffers are driver-owned now as well. But we can't
tell if they all have the same state. So for instance
- the second EQBS reports OUTPUT EMPTY, but any number of the previous
  buffers could be OUTPUT ERROR by now,
- the second EQBS reports OUTPUT ERROR, but any number of the previous
  buffers could be OUTPUT EMPTY by now.

Effectively, this can result in both over- and underreporting of errors.

If the state reported by the second EQBS is 'HW-owned', that doesn't
guarantee that the previous buffers have not been switched to
driver-owned in the mean time. So for instance
- the second EQBS reports INPUT EMPTY, but any number of the previous
  buffers could be INPUT PRIMED (or INPUT ERROR) by now.

This would result in failure to process pending work on the queue. If
it's the final check before yielding initiative, this can cause
a (temporary) queue stall due to IRQ avoidance.

Fixes: 25f269f173 ("[S390] qdio: EQBS retry after CCQ 96")
Cc: <stable@vger.kernel.org> #v3.2+
Signed-off-by: Julian Wiedmann <jwi@linux.vnet.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2018-04-19 08:56:18 +02:00
arch x86/MCE/AMD: Define a function to get SMCA bank type 2018-04-19 08:56:17 +02:00
block block, bfq: put async queues for root bfq groups too 2018-04-12 12:32:19 +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: aes-generic - build with -Os on gcc-7+ 2018-04-12 12:32:20 +02:00
Documentation serial: 8250: Add Nuvoton NPCM UART 2018-04-08 14:26:30 +02:00
drivers s390/qdio: don't retry EQBS after CCQ 96 2018-04-19 08:56:18 +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 VFS: close race between getcwd() and d_move() 2018-04-12 12:32:13 +02:00
include slip: Check if rstate is initialized before uncompressing 2018-04-19 08:56:16 +02:00
init kmemcheck: stop using GFP_NOTRACK and SLAB_NOTRACK 2018-02-22 15:42:23 +01:00
ipc ipc/shm.c: add split function to shm_vm_ops 2018-04-08 14:26:27 +02:00
kernel perf/core: Fix use-after-free in uprobe_perf_close() 2018-04-19 08:56:17 +02:00
lib rhashtable: Fix rhlist duplicates insertion 2018-03-31 18:10:40 +02:00
mm percpu: add __GFP_NORETRY semantics to the percpu balancing path 2018-04-08 14:26:29 +02:00
net rds: MP-RDS may use an invalid c_path 2018-04-19 08:56:15 +02:00
samples samples/bpf: adjust rlimit RLIMIT_MEMLOCK for xdp1 2017-12-20 10:10:31 +01:00
scripts kbuild: fix linker feature test macros when cross compiling with Clang 2018-03-24 11:01:29 +01:00
security apparmor: fix resource audit messages when auditing peer 2018-04-19 08:56:18 +02:00
sound ASoC: Intel: sst: Fix the return value of 'sst_send_byte_stream_mrfld()' 2018-04-12 12:32:17 +02:00
tools perf intel-pt: Fix timestamp following overflow 2018-04-19 08:56:17 +02:00
usr initramfs: fix initramfs rebuilds w/ compression after disabling 2017-11-03 07:39:19 -07:00
virt KVM: arm/arm64: vgic: Don't populate multiple LRs with the same vintid 2018-03-21 12:06:43 +01:00
.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 4.14.34 2018-04-12 12:32:27 +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.