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Peter Zijlstra 32671e3799 perf: Disallow mis-matched inherited group reads 
Because group consistency is non-atomic between parent (filedesc) and children
(inherited) events, it is possible for PERF_FORMAT_GROUP read() to try and sum
non-matching counter groups -- with non-sensical results.

Add group_generation to distinguish the case where a parent group removes and
adds an event and thus has the same number, but a different configuration of
events as inherited groups.

This became a problem when commit fa8c269353 ("perf/core: Invert
perf_read_group() loops") flipped the order of child_list and sibling_list.
Previously it would iterate the group (sibling_list) first, and for each
sibling traverse the child_list. In this order, only the group composition of
the parent is relevant. By flipping the order the group composition of the
child (inherited) events becomes an issue and the mis-match in group
composition becomes evident.

That said; even prior to this commit, while reading of a group that is not
equally inherited was not broken, it still made no sense.

(Ab)use ECHILD as error return to indicate issues with child process group
composition.

Fixes: fa8c269353 ("perf/core: Invert perf_read_group() loops")
Reported-by: Budimir Markovic <markovicbudimir@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20231018115654.GK33217@noisy.programming.kicks-ass.net
2023-10-19 10:09:42 +02:00
arch Revert "x86/smp: Put CPUs into INIT on shutdown if possible" 2023-10-15 12:02:02 -07:00
block
certs
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Documentation Char/Misc driver fixes for 6.6-rc6 2023-10-15 09:07:27 -07:00
drivers virtio_net: fix the missing of the dma cpu sync 2023-10-15 11:49:57 -07:00
fs overlayfs fixes for 6.6-rc6 2023-10-15 08:55:51 -07:00
include perf: Disallow mis-matched inherited group reads 2023-10-19 10:09:42 +02:00
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kernel perf: Disallow mis-matched inherited group reads 2023-10-19 10:09:42 +02:00
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net Fixes for an overreaching WARN_ON, two error paths and a switch to 2023-10-13 11:27:31 -07:00
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tools RISC-V Fixes for 6.6-rc6 2023-10-13 09:17:48 -07:00
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MAINTAINERS Char/Misc driver fixes for 6.6-rc6 2023-10-15 09:07:27 -07:00
Makefile Linux 6.6-rc6 2023-10-15 13:34:39 -07:00
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.