Tejun Heo 8a2fbdd5b0 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>		2019-01-09 17:38:45 +01:00
..
cgroup-internal.h	cgroup/tracing: Move taking of spin lock out of trace event handlers	2018-07-11 10:48:47 -07:00
cgroup-v1.c	cgroup/tracing: Move taking of spin lock out of trace event handlers	2018-07-11 10:48:47 -07:00
cgroup.c	cgroup: fix CSS_TASK_ITER_PROCS	2019-01-09 17:38:45 +01:00
cpuset.c	docs: Fix some broken references	2018-06-15 18:10:01 -03:00
debug.c	debug cgroup: use task_css_set instead of rcu_dereference	2017-11-27 11:37:33 -08:00
freezer.c	cgroup: add @flags to css_task_iter_start() and implement CSS_TASK_ITER_PROCS	2017-07-21 11:14:51 -04:00
Makefile	cgroup: Rename kernel/cgroup/stat.c to kernel/cgroup/rstat.c	2018-04-26 14:29:04 -07:00
namespace.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
pids.c	cgroup: implement cgroup v2 thread support	2017-07-21 11:14:51 -04:00
rdma.c	rdmacg: Convert to use match_string() helper	2018-05-07 09:27:26 -07:00
rstat.c	cgroup: Make cgroup_rstat_updated() ready for root cgroup usage	2018-04-26 14:29:06 -07:00