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James Clark a3486ef99a perf: Always wake the parent event 
[ Upstream commit 961c391217 ]

When using per-process mode and event inheritance is set to true,
forked processes will create a new perf events via inherit_event() ->
perf_event_alloc(). But these events will not have ring buffers
assigned to them. Any call to wakeup will be dropped if it's called on
an event with no ring buffer assigned because that's the object that
holds the wakeup list.

If the child event is disabled due to a call to
perf_aux_output_begin() or perf_aux_output_end(), the wakeup is
dropped leaving userspace hanging forever on the poll.

Normally the event is explicitly re-enabled by userspace after it
wakes up to read the aux data, but in this case it does not get woken
up so the event remains disabled.

This can be reproduced when using Arm SPE and 'stress' which forks once
before running the workload. By looking at the list of aux buffers read,
it's apparent that they stop after the fork:

  perf record -e arm_spe// -vvv -- stress -c 1

With this patch applied they continue to be printed. This behaviour
doesn't happen when using systemwide or per-cpu mode.

Reported-by: Ruben Ayrapetyan <Ruben.Ayrapetyan@arm.com>
Signed-off-by: James Clark <james.clark@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211206113840.130802-2-james.clark@arm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-02-16 12:56:15 +01:00
arch powerpc/fixmap: Fix VM debug warning on unmap 2022-02-16 12:56:12 +01:00
block block: bio-integrity: Advance seed correctly for larger interval sizes 2022-02-08 18:34:05 +01:00
certs
crypto crypto: api - Move cryptomgr soft dependency into algapi 2022-02-11 09:10:26 +01:00
Documentation Revert "fbcon: Disable accelerated scrolling" 2022-02-08 18:34:06 +01:00
drivers usb: dwc2: gadget: don't try to disable ep0 in dwc2_hsotg_suspend 2022-02-16 12:56:15 +01:00
fs NFSv4 handle port presence in fs_location server string 2022-02-16 12:56:10 +01:00
include PM: hibernate: Remove register_nosave_region_late() 2022-02-16 12:56:15 +01:00
init init: make unknown command line param message clearer 2021-11-18 19:17:11 +01:00
ipc ipc/sem: do not sleep with a spin lock held 2022-02-08 18:34:03 +01:00
kernel perf: Always wake the parent event 2022-02-16 12:56:15 +01:00
lib lib/test_meminit: destroy cache in kmem_cache_alloc_bulk() test 2022-01-27 11:05:44 +01:00
LICENSES
mm mm/kmemleak: avoid scanning potential huge holes 2022-02-08 18:34:05 +01:00
net net: sched: Clarify error message when qdisc kind is unknown 2022-02-16 12:56:12 +01:00
samples samples: bpf: Fix 'unknown warning group' build warning on Clang 2022-01-27 11:03:29 +01:00
scripts scripts: sphinx-pre-install: Fix ctex support on Debian 2022-01-27 11:05:44 +01:00
security ima: Do not print policy rule with inactive LSM labels 2022-02-16 12:56:04 +01:00
sound ASoC: codecs: wcd938x: fix return value of mixer put function 2022-02-08 18:34:11 +01:00
tools selftests: netfilter: check stateless nat udp checksum fixup 2022-02-08 18:34:14 +01:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:27:15 +01:00
virt Revert "KVM: SVM: avoid infinite loop on NPF from bad address" 2022-02-01 17:27:01 +01:00
.clang-format
.cocciconfig
.get_maintainer.ignore
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.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
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MAINTAINERS drm fixes for 5.15 final 2021-10-28 12:17:01 -07:00
Makefile Linux 5.15.23 2022-02-11 09:10:27 +01:00
README

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.

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.