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Filename Latest commit message Latest commit date
Oleg Nesterov 51bee5abea cgroup/pids: turn cgroup_subsys->free() into cgroup_subsys->release() to fix the accounting
The only user of cgroup_subsys->free() callback is pids_cgrp_subsys which
needs pids_free() to uncharge the pid.

However, ->free() is called from __put_task_struct()->cgroup_free() and this
is too late. Even the trivial program which does

	for (;;) {
		int pid = fork();
		assert(pid >= 0);
		if (pid)
			wait(NULL);
		else
			exit(0);
	}

can run out of limits because release_task()->call_rcu(delayed_put_task_struct)
implies an RCU gp after the task/pid goes away and before the final put().

Test-case:

	mkdir -p /tmp/CG
	mount -t cgroup2 none /tmp/CG
	echo '+pids' > /tmp/CG/cgroup.subtree_control

	mkdir /tmp/CG/PID
	echo 2 > /tmp/CG/PID/pids.max

	perl -e 'while ($p = fork) { wait; } $p // die "fork failed: $!\n"' &
	echo $! > /tmp/CG/PID/cgroup.procs

Without this patch the forking process fails soon after migration.

Rename cgroup_subsys->free() to cgroup_subsys->release() and move the callsite
into the new helper, cgroup_release(), called by release_task() which actually
frees the pid(s).

Reported-by: Herton R. Krzesinski <hkrzesin@redhat.com>
Reported-by: Jan Stancek <jstancek@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
2019-01-31 06:55:57 -08:00
arch Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-01-27 12:02:00 -08:00
block Revert "block: cover another queue enter recursion via BIO_QUEUE_ENTERED" 2019-01-27 06:35:28 -07:00
certs
crypto
Documentation fs/dcache: Track & report number of negative dentries 2019-01-30 11:02:11 -08:00
drivers IOMMU Fixes for Linux v5.0-rc4 2019-01-30 09:30:03 -08:00
firmware
fs fs/dcache: Track & report number of negative dentries 2019-01-30 11:02:11 -08:00
include cgroup/pids: turn cgroup_subsys->free() into cgroup_subsys->release() to fix the accounting 2019-01-31 06:55:57 -08:00
init
ipc
kernel cgroup/pids: turn cgroup_subsys->free() into cgroup_subsys->release() to fix the accounting 2019-01-31 06:55:57 -08:00
lib XArray updates for 5.0-rc3 2019-01-22 17:08:30 +13:00
LICENSES
mm Revert "mm, memory_hotplug: initialize struct pages for the full memory section" 2019-01-28 10:35:22 -08:00
net net: set default network namespace in init_dummy_netdev() 2019-01-29 11:29:55 -08:00
samples samples/bpf: workaround clang asm goto compilation errors 2019-01-15 20:57:30 +01:00
scripts Bug fixes for gcc-plugins 2019-01-21 13:07:03 +13:00
security Merge branch 'fixes-v5.0-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2019-01-17 16:54:58 +12:00
sound sound fixes for 5.0-rc4 2019-01-25 05:55:26 +13:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-01-29 17:11:47 -08:00
usr
virt
.clang-format clang-format: Update .clang-format with the latest for_each macro list 2019-01-19 19:26:06 +01:00
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
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COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS MAINTAINERS: Add entry for XDP (eXpress Data Path) 2019-01-29 11:40:51 -08:00
Makefile Linux 5.0-rc4 2019-01-27 15:18:05 -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.