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Filename Latest commit message Latest commit date
Petr Mladek d697bad588 livepatch: Remove Nop structures when unused
Replaced patches are removed from the stack when the transition is
finished. It means that Nop structures will never be needed again
and can be removed. Why should we care?

  + Nop structures give the impression that the function is patched
    even though the ftrace handler has no effect.

  + Ftrace handlers do not come for free. They cause slowdown that might
    be visible in some workloads. The ftrace-related slowdown might
    actually be the reason why the function is no longer patched in
    the new cumulative patch. One would expect that cumulative patch
    would help solve these problems as well.

  + Cumulative patches are supposed to replace any earlier version of
    the patch. The amount of NOPs depends on which version was replaced.
    This multiplies the amount of scenarios that might happen.

    One might say that NOPs are innocent. But there are even optimized
    NOP instructions for different processors, for example, see
    arch/x86/kernel/alternative.c. And klp_ftrace_handler() is much
    more complicated.

  + It sounds natural to clean up a mess that is no longer needed.
    It could only be worse if we do not do it.

This patch allows to unpatch and free the dynamic structures independently
when the transition finishes.

The free part is a bit tricky because kobject free callbacks are called
asynchronously. We could not wait for them easily. Fortunately, we do
not have to. Any further access can be avoided by removing them from
the dynamic lists.

Signed-off-by: Petr Mladek <pmladek@suse.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2019-01-11 20:51:24 +01:00
arch It appears that the zero-day bot did find a bug in my sh build. 2019-01-05 14:08:00 -08:00
block for-4.21/block-20190102 2019-01-02 18:49:58 -08:00
certs
crypto Kconfig updates for v4.21 2018-12-29 13:03:29 -08:00
Documentation livepatch: Add atomic replace 2019-01-11 20:51:24 +01:00
drivers Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/rzhang/linux 2019-01-05 16:07:28 -08:00
firmware
fs three fixes, one for stable, one adds the (most secure) SMB3.1.1 dialect to default list requested 2019-01-05 14:05:06 -08:00
include livepatch: Add atomic replace 2019-01-11 20:51:24 +01:00
init Merge branch 'mount.part1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-01-05 13:25:58 -08:00
ipc
kernel livepatch: Remove Nop structures when unused 2019-01-11 20:51:24 +01:00
lib lib/genalloc.c: include vmalloc.h 2019-01-05 13:54:53 -08:00
LICENSES
mm Merge branch 'akpm' (patches from Andrew) 2019-01-05 09:16:18 -08:00
net A fairly quiet round: a couple of messenger performance improvements 2019-01-05 13:58:08 -08:00
samples livepatch: Simplify API by removing registration step 2019-01-11 20:51:24 +01:00
scripts Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-01-05 13:18:59 -08:00
security Merge branch 'mount.part1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-01-05 13:25:58 -08:00
sound Remove 'type' argument from access_ok() function 2019-01-03 18:57:57 -08:00
tools Merge branch 'akpm' (patches from Andrew) 2019-01-05 09:16:18 -08:00
usr
virt Merge branch 'akpm' (patches from Andrew) 2019-01-05 09:16:18 -08:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap A few early MIPS fixes for 4.21: 2019-01-05 12:48:25 -08:00
COPYING
CREDITS
Kbuild kbuild: remove unused cmd_gentimeconst 2018-12-25 00:10:30 +09:00
Kconfig
MAINTAINERS Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/evalenti/linux-soc-thermal 2019-01-05 16:01:16 -08:00
Makefile Kbuild updates for v4.21 2018-12-29 12:03:17 -08:00
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.

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.