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Tejun Heo 23bd93f406 cgroup: fix CSS_TASK_ITER_PROCS
commit e9d81a1bc2 upstream.

CSS_TASK_ITER_PROCS implements process-only iteration by making
css_task_iter_advance() skip tasks which aren't threadgroup leaders;
however, when an iteration is started css_task_iter_start() calls the
inner helper function css_task_iter_advance_css_set() instead of
css_task_iter_advance().  As the helper doesn't have the skip logic,
when the first task to visit is a non-leader thread, it doesn't get
skipped correctly as shown in the following example.

  # ps -L 2030
    PID   LWP TTY      STAT   TIME COMMAND
   2030  2030 pts/0    Sl+    0:00 ./test-thread
   2030  2031 pts/0    Sl+    0:00 ./test-thread
  # mkdir -p /sys/fs/cgroup/x/a/b
  # echo threaded > /sys/fs/cgroup/x/a/cgroup.type
  # echo threaded > /sys/fs/cgroup/x/a/b/cgroup.type
  # echo 2030 > /sys/fs/cgroup/x/a/cgroup.procs
  # cat /sys/fs/cgroup/x/a/cgroup.threads
  2030
  2031
  # cat /sys/fs/cgroup/x/cgroup.procs
  2030
  # echo 2030 > /sys/fs/cgroup/x/a/b/cgroup.threads
  # cat /sys/fs/cgroup/x/cgroup.procs
  2031
  2030

The last read of cgroup.procs is incorrectly showing non-leader 2031
in cgroup.procs output.

This can be fixed by updating css_task_iter_advance() to handle the
first advance and css_task_iters_tart() to call
css_task_iter_advance() instead of the inner helper.  After the fix,
the same commands result in the following (correct) result:

  # ps -L 2062
    PID   LWP TTY      STAT   TIME COMMAND
   2062  2062 pts/0    Sl+    0:00 ./test-thread
   2062  2063 pts/0    Sl+    0:00 ./test-thread
  # mkdir -p /sys/fs/cgroup/x/a/b
  # echo threaded > /sys/fs/cgroup/x/a/cgroup.type
  # echo threaded > /sys/fs/cgroup/x/a/b/cgroup.type
  # echo 2062 > /sys/fs/cgroup/x/a/cgroup.procs
  # cat /sys/fs/cgroup/x/a/cgroup.threads
  2062
  2063
  # cat /sys/fs/cgroup/x/cgroup.procs
  2062
  # echo 2062 > /sys/fs/cgroup/x/a/b/cgroup.threads
  # cat /sys/fs/cgroup/x/cgroup.procs
  2062

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
Fixes: 8cfd8147df ("cgroup: implement cgroup v2 thread support")
Cc: stable@vger.kernel.org # v4.14+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2019-01-09 17:45:59 +01:00
arch clocksource/drivers/arc_timer: Utilize generic sched_clock 2019-01-09 17:45:55 +01:00
block block: Fix null_blk_zoned creation failure with small number of zones 2018-12-11 16:19:38 -07:00
certs export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR() 2018-08-22 23:21:44 +09:00
crypto crypto: cfb - fix decryption 2019-01-09 17:45:59 +01:00
Documentation x86/speculation/l1tf: Drop the swap storage limit restriction when l1tf=off 2019-01-09 17:45:54 +01:00
drivers crypto: chcr - small packet Tx stalls the queue 2019-01-09 17:45:59 +01:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs ext4: check for shutdown and r/o file system in ext4_write_inode() 2019-01-09 17:45:58 +01:00
include ext4: force inode writes when nfsd calls commit_metadata() 2019-01-09 17:45:58 +01:00
init psi: fix reference to kernel commandline enable 2018-12-14 15:05:45 -08:00
ipc ipc: IPCMNI limit check for semmni 2018-10-31 08:54:14 -07:00
kernel cgroup: fix CSS_TASK_ITER_PROCS 2019-01-09 17:45:59 +01:00
lib XArray: Fix xa_alloc when id exceeds max 2018-12-13 14:07:33 -05:00
LICENSES This is a fairly typical cycle for documentation. There's some welcome 2018-10-24 18:01:11 +01:00
mm mm, page_alloc: fix has_unmovable_pages for HugePages 2018-12-21 14:51:18 -08:00
net tipc: fix a double free in tipc_enable_bearer() 2019-01-09 17:45:51 +01:00
samples VFIO updates for v4.20 2018-10-31 11:01:38 -07:00
scripts Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-12-21 09:22:24 -08:00
security ima: cleanup the match_token policy code 2018-12-17 16:31:28 -08:00
sound ASoC: intel: cht_bsw_max98090_ti: Add pmc_plt_clk_0 quirk for Chromebook Gnawty 2019-01-09 17:45:54 +01:00
tools perf env: Also consider env->arch == NULL as local operation 2019-01-09 17:45:56 +01:00
usr initramfs: move gen_initramfs_list.sh from scripts/ to usr/ 2018-08-22 23:21:44 +09:00
virt KVM: fix unregistering coalesced mmio zone from wrong bus 2018-12-18 22:07:25 +01:00
.clang-format page cache: Convert find_get_pages_contig to XArray 2018-10-21 10:46:34 -04:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap mailmap: Update email for Punit Agrawal 2018-11-05 10:02:11 +00:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: update entry for MMP platform 2018-12-03 12:39:57 -08:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-12-21 14:21:17 -08:00
Makefile Linux 4.20 2018-12-23 15:55:59 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.