linux-stable.git/kernel/cgroup/cpuset.c, branch linux-5.14.y

cgroup/cpuset: Fix violation of cpuset locking rule

2021-09-15T08:02:21+00:00

[ Upstream commit 6ba34d3c73674e46d9e126e4f0cee79e5ef2481c ]

The cpuset fields that manage partition root state do not strictly
follow the cpuset locking rule that update to cpuset has to be done
with both the callback_lock and cpuset_mutex held. This is now fixed
by making sure that the locking rule is upheld.

Fixes: 3881b86128d0 ("cpuset: Add an error state to cpuset.sched.partition")
Fixes: 4b842da276a8 ("cpuset: Make CPU hotplug work with partition")
Signed-off-by: Waiman Long 
Signed-off-by: Tejun Heo 
Signed-off-by: Sasha Levin

cgroup/cpuset: Miscellaneous code cleanup

2021-09-15T08:02:21+00:00

[ Upstream commit 0f3adb8a1e5f36e792598c1d77a2cfac9c90a4f9 ]

Use more descriptive variable names for update_prstate(), remove
unnecessary code and fix some typos. There is no functional change.

Signed-off-by: Waiman Long 
Signed-off-by: Tejun Heo 
Signed-off-by: Sasha Levin

cgroup/cpuset: Fix a partition bug with hotplug

2021-09-15T08:02:15+00:00

[ Upstream commit 15d428e6fe77fffc3f4fff923336036f5496ef17 ]

In cpuset_hotplug_workfn(), the detection of whether the cpu list
has been changed is done by comparing the effective cpus of the top
cpuset with the cpu_active_mask. However, in the rare case that just
all the CPUs in the subparts_cpus are offlined, the detection fails
and the partition states are not updated correctly. Fix it by forcing
the cpus_updated flag to true in this particular case.

Fixes: 4b842da276a8 ("cpuset: Make CPU hotplug work with partition")
Signed-off-by: Waiman Long 
Signed-off-by: Tejun Heo 
Signed-off-by: Sasha Levin

cgroup: fix spelling mistakes

2021-05-24T16:45:26+00:00

Fix some spelling mistakes in comments:
hierarhcy ==> hierarchy
automtically ==> automatically
overriden ==> overridden
In absense of .. or ==> In absence of .. and
assocaited ==> associated
taget ==> target
initate ==> initiate
succeded ==> succeeded
curremt ==> current
udpated ==> updated

Signed-off-by: Zhen Lei 
Signed-off-by: Tejun Heo

cgroup/cpuset: fix typos in comments

2021-04-12T21:20:53+00:00

Change hierachy to hierarchy and unrechable to unreachable,
no functionality changed.

Signed-off-by: Lu Jialin 
Signed-off-by: Tejun Heo

cpuset: fix typos in comments

2021-01-15T20:36:41+00:00

Change hierachy to hierarchy and congifured to configured, no functionality
changed.

Signed-off-by: Aubrey Li 
Reviewed-by: Randy Dunlap 
Signed-off-by: Tejun Heo

cpuset: fix race between hotplug work and later CPU offline

2020-11-19T10:25:45+00:00

One of our machines keeled over trying to rebuild the scheduler domains.
Mainline produces the same splat:

  BUG: unable to handle page fault for address: 0000607f820054db
  CPU: 2 PID: 149 Comm: kworker/1:1 Not tainted 5.10.0-rc1-master+ #6
  Workqueue: events cpuset_hotplug_workfn
  RIP: build_sched_domains
  Call Trace:
   partition_sched_domains_locked
   rebuild_sched_domains_locked
   cpuset_hotplug_workfn

It happens with cgroup2 and exclusive cpusets only.  This reproducer
triggers it on an 8-cpu vm and works most effectively with no
preexisting child cgroups:

  cd $UNIFIED_ROOT
  mkdir cg1
  echo 4-7 > cg1/cpuset.cpus
  echo root > cg1/cpuset.cpus.partition

  # with smt/control reading 'on',
  echo off > /sys/devices/system/cpu/smt/control

RIP maps to

  sd->shared = *per_cpu_ptr(sdd->sds, sd_id);

from sd_init().  sd_id is calculated earlier in the same function:

  cpumask_and(sched_domain_span(sd), cpu_map, tl->mask(cpu));
  sd_id = cpumask_first(sched_domain_span(sd));

tl->mask(cpu), which reads cpu_sibling_map on x86, returns an empty mask
and so cpumask_first() returns >= nr_cpu_ids, which leads to the bogus
value from per_cpu_ptr() above.

The problem is a race between cpuset_hotplug_workfn() and a later
offline of CPU N.  cpuset_hotplug_workfn() updates the effective masks
when N is still online, the offline clears N from cpu_sibling_map, and
then the worker uses the stale effective masks that still have N to
generate the scheduling domains, leading the worker to read
N's empty cpu_sibling_map in sd_init().

rebuild_sched_domains_locked() prevented the race during the cgroup2
cpuset series up until the Fixes commit changed its check.  Make the
check more robust so that it can detect an offline CPU in any exclusive
cpuset's effective mask, not just the top one.

Fixes: 0ccea8feb980 ("cpuset: Make generate_sched_domains() work with partition")
Signed-off-by: Daniel Jordan 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Tejun Heo 
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20201112171711.639541-1-daniel.m.jordan@oracle.com

kernel/: fix repeated words in comments

2020-10-16T18:11:19+00:00

Fix multiple occurrences of duplicated words in kernel/.

Fix one typo/spello on the same line as a duplicate word.  Change one
instance of "the the" to "that the".  Otherwise just drop one of the
repeated words.

Signed-off-by: Randy Dunlap 
Signed-off-by: Andrew Morton 
Link: https://lkml.kernel.org/r/98202fa6-8919-ef63-9efe-c0fad5ca7af1@infradead.org
Signed-off-by: Linus Torvalds

mmap locking API: convert mmap_sem comments

2020-06-09T16:39:14+00:00

Convert comments that reference mmap_sem to reference mmap_lock instead.

[akpm@linux-foundation.org: fix up linux-next leftovers]
[akpm@linux-foundation.org: s/lockaphore/lock/, per Vlastimil]
[akpm@linux-foundation.org: more linux-next fixups, per Michel]

Signed-off-by: Michel Lespinasse 
Signed-off-by: Andrew Morton 
Reviewed-by: Vlastimil Babka 
Reviewed-by: Daniel Jordan 
Cc: Davidlohr Bueso 
Cc: David Rientjes 
Cc: Hugh Dickins 
Cc: Jason Gunthorpe 
Cc: Jerome Glisse 
Cc: John Hubbard 
Cc: Laurent Dufour 
Cc: Liam Howlett 
Cc: Matthew Wilcox 
Cc: Peter Zijlstra 
Cc: Ying Han 
Link: http://lkml.kernel.org/r/20200520052908.204642-13-walken@google.com
Signed-off-by: Linus Torvalds

docs: cgroup-v1: Document the cpuset_v2_mode mount option

2020-04-03T15:42:56+00:00

The cpuset in cgroup v1 accepts a special "cpuset_v2_mode" mount
option that make cpuset.cpus and cpuset.mems behave more like those in
cgroup v2.  Document it to make other people more aware of this feature
that can be useful in some circumstances.

Signed-off-by: Waiman Long 
Signed-off-by: Tejun Heo