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Kan Liang d31fc13fdc perf/x86/intel: Fix event update for auto-reload There is a bug when reading event->count with large PEBS enabled. Here is an example: # ./read_count 0x71f0 0x122c0 0x1000000001c54 0x100000001257d 0x200000000bdc5 In fixed period mode, the auto-reload mechanism could be enabled for PEBS events, but the calculation of event->count does not take the auto-reload values into account. Anyone who reads event->count will get the wrong result, e.g x86_pmu_read(). This bug was introduced with the auto-reload mechanism enabled since commit: `851559e35f` ("perf/x86/intel: Use the PEBS auto reload mechanism when possible") Introduce intel_pmu_save_and_restart_reload() to calculate the event->count only for auto-reload. Since the counter increments a negative counter value and overflows on the sign switch, giving the interval: [-period, 0] the difference between two consequtive reads is: A) value2 - value1; when no overflows have happened in between, B) (0 - value1) + (value2 - (-period)); when one overflow happened in between, C) (0 - value1) + (n - 1) * (period) + (value2 - (-period)); when @n overflows happened in between. Here A) is the obvious difference, B) is the extension to the discrete interval, where the first term is to the top of the interval and the second term is from the bottom of the next interval and C) the extension to multiple intervals, where the middle term is the whole intervals covered. The equation for all cases is: value2 - value1 + n * period Previously the event->count is updated right before the sample output. But for case A, there is no PEBS record ready. It needs to be specially handled. Remove the auto-reload code from x86_perf_event_set_period() since we'll not longer call that function in this case. Based-on-code-from: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Kan Liang <kan.liang@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: acme@kernel.org Fixes: `851559e35f` ("perf/x86/intel: Use the PEBS auto reload mechanism when possible") Link: http://lkml.kernel.org/r/1518474035-21006-2-git-send-email-kan.liang@linux.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>		2018-03-09 08:22:19 +01:00
arch	perf/x86/intel: Fix event update for auto-reload	2018-03-09 08:22:19 +01:00
block	for-linus-20180302	2018-03-02 09:35:36 -08:00
certs	certs/blacklist_nohashes.c: fix const confusion in certs blacklist	2018-02-21 15:35:43 -08:00
crypto	X.509: fix NULL dereference when restricting key with unsupported_sig	2018-02-22 14:38:34 +00:00
Documentation	Linux 4.16-rc4	2018-03-06 07:30:22 +01:00
drivers	Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2018-03-04 11:34:49 -08:00
firmware	kbuild: remove all dummy assignments to obj-	2017-11-18 11:46:06 +09:00
fs	for-4.16-rc3-tag	2018-03-04 11:04:27 -08:00
include	Linux 4.16-rc4	2018-03-06 07:30:22 +01:00
init	jump_label: Explicitly disable jump labels in __init code	2018-02-21 16:54:05 +01:00
ipc	vfs: do bulk POLL* -> EPOLL* replacement	2018-02-11 14:34:03 -08:00
kernel	Linux 4.16-rc4	2018-03-06 07:30:22 +01:00
lib	A single fix for a memory leak regression in the dma-debug code.	2018-02-28 11:13:08 -08:00
LICENSES	LICENSES: Add MPL-1.1 license	2018-01-06 10:59:44 -07:00
mm	mm: don't defer struct page initialization for Xen pv guests	2018-02-21 15:35:43 -08:00
net	libceph, ceph: avoid memory leak when specifying same option several times	2018-02-26 16:19:30 +01:00
samples	- do not build samples when cross compiling (Michal Hocko)	2018-02-27 10:39:29 -08:00
scripts	Kbuild fixes for v4.16	2018-03-03 10:37:01 -08:00
security	integrity/security: fix digsig.c build error with header file	2018-02-22 20:09:08 -08:00
sound	ALSA: x86: Fix potential crash at error path	2018-02-28 08:46:00 +01:00
tools	Merge branch 'perf/urgent' into perf/core, to resolve conflict	2018-03-07 09:23:12 +01:00
usr	initramfs: fix initramfs rebuilds w/ compression after disabling	2017-11-03 07:39:19 -07:00
virt	KVM: mmu: Fix overlap between public and private memslots	2018-02-24 01:43:36 +01:00
.cocciconfig	scripts: add Linux .cocciconfig for coccinelle	2016-07-22 12:13:39 +02:00
.get_maintainer.ignore
.gitattributes	.gitattributes: set git diff driver for C source code files	2016-10-07 18:46:30 -07:00
.gitignore	.gitignore: ignore ASN.1 auto generated files	2018-02-14 21:05:38 +01:00
.mailmap	mailmap: update Mark Yao's email address	2018-01-04 16:45:09 -08:00
COPYING
CREDITS	MAINTAINERS: update TPM driver infrastructure changes	2017-11-09 17:58:40 -08:00
Kbuild	Kbuild updates for v4.15	2017-11-17 17:45:29 -08:00
Kconfig	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
MAINTAINERS	Kbuild fixes for v4.16	2018-03-03 10:37:01 -08:00
Makefile	Linux 4.16-rc4	2018-03-04 14:54:11 -08:00
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.