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Thomas Richter fbf01d59bc s390/cpum_sf: Avoid SBD overflow condition in irq handler 
[ Upstream commit 0539ad0b22 ]

The s390 CPU Measurement sampling facility has an overflow condition
which fires when all entries in a SBD are used.
The measurement alert interrupt is triggered and reads out all samples
in this SDB. It then tests the successor SDB, if this SBD is not full,
the interrupt handler does not read any samples at all from this SDB
The design waits for the hardware to fill this SBD and then trigger
another meassurement alert interrupt.

This scheme works nicely until
an perf_event_overflow() function call discards the sample due to
a too high sampling rate.
The interrupt handler has logic to read out a partially filled SDB
when the perf event overflow condition in linux common code is met.
This causes the CPUM sampling measurement hardware and the PMU
device driver to operate on the same SBD's trailer entry.
This should not happen.

This can be seen here using this trace:
   cpumsf_pmu_add: tear:0xb5286000
   hw_perf_event_update: sdbt 0xb5286000 full 1 over 0 flush_all:0
   hw_perf_event_update: sdbt 0xb5286008 full 0 over 0 flush_all:0
        above shows 1. interrupt
   hw_perf_event_update: sdbt 0xb5286008 full 1 over 0 flush_all:0
   hw_perf_event_update: sdbt 0xb5286008 full 0 over 0 flush_all:0
        above shows 2. interrupt
	... this goes on fine until...
   hw_perf_event_update: sdbt 0xb5286068 full 1 over 0 flush_all:0
   perf_push_sample1: overflow
      one or more samples read from the IRQ handler are rejected by
      perf_event_overflow() and the IRQ handler advances to the next SDB
      and modifies the trailer entry of a partially filled SDB.
   hw_perf_event_update: sdbt 0xb5286070 full 0 over 0 flush_all:1
      timestamp: 14:32:52.519953

Next time the IRQ handler is called for this SDB the trailer entry shows
an overflow count of 19 missed entries.
   hw_perf_event_update: sdbt 0xb5286070 full 1 over 19 flush_all:1
      timestamp: 14:32:52.970058

Remove access to a follow on SDB when event overflow happened.

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2020-01-09 10:18:58 +01:00
arch s390/cpum_sf: Avoid SBD overflow condition in irq handler 2020-01-09 10:18:58 +01:00
block blk-mq: make sure that line break can be printed 2019-12-17 20:35:48 +01:00
certs export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR() 2018-08-22 23:21:44 +09:00
crypto crypto: user - fix memory leak in crypto_report 2019-12-13 08:52:48 +01:00
Documentation mm, thp, proc: report THP eligibility for each vma 2019-12-17 20:35:45 +01:00
drivers md: raid1: check rdev before reference in raid1_sync_request func 2020-01-09 10:18:57 +01:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs afs: Fix creation calls in the dynamic root to fail with EOPNOTSUPP 2020-01-09 10:18:57 +01:00
include nvme_fc: add module to ops template to allow module references 2020-01-09 10:18:54 +01:00
init fork: fix some -Wmissing-prototypes warnings 2019-12-05 09:21:04 +01:00
ipc ipc/mqueue.c: only perform resource calculation if user valid 2019-08-06 19:06:52 +02:00
kernel ptp: fix the race between the release of ptp_clock and cdev 2020-01-04 19:13:35 +01:00
lib idr: Fix idr_get_next_ul race with idr_remove 2019-12-17 20:36:02 +01:00
LICENSES LICENSES: Remove CC-BY-SA-4.0 license text 2018-10-18 11:28:50 +02:00
mm mm, thp, proc: report THP eligibility for each vma 2019-12-17 20:35:45 +01:00
net net: make socket read/write_iter() honor IOCB_NOWAIT 2020-01-09 10:18:57 +01:00
samples samples: pktgen: fix proc_cmd command result check logic 2019-12-31 16:34:59 +01:00
scripts scripts/kallsyms: fix definitely-lost memory leak 2020-01-04 19:13:09 +01:00
security apparmor: fix unsigned len comparison with less than zero 2020-01-04 19:13:08 +01:00
sound ALSA: hda - Downgrade error message for single-cmd fallback 2020-01-04 19:13:22 +01:00
tools perf strbuf: Remove redundant va_end() in strbuf_addv() 2020-01-04 19:13:24 +01:00
usr kbuild: clean compressed initramfs image 2019-10-07 18:57:16 +02:00
virt KVM: arm/arm64: vgic: Don't rely on the wrong pending table 2019-12-13 08:52:45 +01:00
.clang-format clang-format: Set IndentWrappedFunctionNames false 2018-08-01 18:38:51 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap libnvdimm-for-4.19_misc 2018-08-25 18:13:10 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS 9p: remove Ron Minnich from MAINTAINERS 2018-08-17 16:20:26 -07:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS USB: rio500: Remove Rio 500 kernel driver 2019-10-17 13:44:47 -07:00
Makefile Linux 4.19.93 2020-01-04 19:13:46 +01:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -06:00

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.