linux.git/include/linux/cgroup.h, branch v5.2-rc4 Linux kernel source tree cgroup: get rid of cgroup_freezer_frozen_exit() 2019-05-06T15:39:11+00:00 Roman Gushchin guro@fb.com 2019-04-26T17:59:45+00:00 96b9c592def5d7203bdad1337d9c92a2183de5cb A task should never enter the exit path with the task->frozen bit set. Any frozen task must enter the signal handling loop and the only way to escape is through cgroup_leave_frozen(true), which unconditionally drops the task->frozen bit. So it means that cgroyp_freezer_frozen_exit() has zero chances to be called and has to be removed. Let's put a WARN_ON_ONCE() instead of the cgroup_freezer_frozen_exit() call to catch any potential leak of the task's frozen bit. Suggested-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Roman Gushchin <guro@fb.com> Signed-off-by: Tejun Heo <tj@kernel.org> 
A task should never enter the exit path with the task->frozen bit set.
Any frozen task must enter the signal handling loop and the only
way to escape is through cgroup_leave_frozen(true), which
unconditionally drops the task->frozen bit. So it means that
cgroyp_freezer_frozen_exit() has zero chances to be called and
has to be removed.

Let's put a WARN_ON_ONCE() instead of the cgroup_freezer_frozen_exit()
call to catch any potential leak of the task's frozen bit.

Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
cgroup: cgroup v2 freezer 2019-04-19T18:26:48+00:00 Roman Gushchin guro@fb.com 2019-04-19T17:03:04+00:00 76f969e8948d82e78e1bc4beb6b9465908e74873 Cgroup v1 implements the freezer controller, which provides an ability to stop the workload in a cgroup and temporarily free up some resources (cpu, io, network bandwidth and, potentially, memory) for some other tasks. Cgroup v2 lacks this functionality. This patch implements freezer for cgroup v2. Cgroup v2 freezer tries to put tasks into a state similar to jobctl stop. This means that tasks can be killed, ptraced (using PTRACE_SEIZE*), and interrupted. It is possible to attach to a frozen task, get some information (e.g. read registers) and detach. It's also possible to migrate a frozen tasks to another cgroup. This differs cgroup v2 freezer from cgroup v1 freezer, which mostly tried to imitate the system-wide freezer. However uninterruptible sleep is fine when all tasks are going to be frozen (hibernation case), it's not the acceptable state for some subset of the system. Cgroup v2 freezer is not supporting freezing kthreads. If a non-root cgroup contains kthread, the cgroup still can be frozen, but the kthread will remain running, the cgroup will be shown as non-frozen, and the notification will not be delivered. * PTRACE_ATTACH is not working because non-fatal signal delivery is blocked in frozen state. There are some interface differences between cgroup v1 and cgroup v2 freezer too, which are required to conform the cgroup v2 interface design principles: 1) There is no separate controller, which has to be turned on: the functionality is always available and is represented by cgroup.freeze and cgroup.events cgroup control files. 2) The desired state is defined by the cgroup.freeze control file. Any hierarchical configuration is allowed. 3) The interface is asynchronous. The actual state is available using cgroup.events control file ("frozen" field). There are no dedicated transitional states. 4) It's allowed to make any changes with the cgroup hierarchy (create new cgroups, remove old cgroups, move tasks between cgroups) no matter if some cgroups are frozen. Signed-off-by: Roman Gushchin <guro@fb.com> Signed-off-by: Tejun Heo <tj@kernel.org> No-objection-from-me-by: Oleg Nesterov <oleg@redhat.com> Cc: kernel-team@fb.com 
Cgroup v1 implements the freezer controller, which provides an ability
to stop the workload in a cgroup and temporarily free up some
resources (cpu, io, network bandwidth and, potentially, memory)
for some other tasks. Cgroup v2 lacks this functionality.

This patch implements freezer for cgroup v2.

Cgroup v2 freezer tries to put tasks into a state similar to jobctl
stop. This means that tasks can be killed, ptraced (using
PTRACE_SEIZE*), and interrupted. It is possible to attach to
a frozen task, get some information (e.g. read registers) and detach.
It's also possible to migrate a frozen tasks to another cgroup.

This differs cgroup v2 freezer from cgroup v1 freezer, which mostly
tried to imitate the system-wide freezer. However uninterruptible
sleep is fine when all tasks are going to be frozen (hibernation case),
it's not the acceptable state for some subset of the system.

Cgroup v2 freezer is not supporting freezing kthreads.
If a non-root cgroup contains kthread, the cgroup still can be frozen,
but the kthread will remain running, the cgroup will be shown
as non-frozen, and the notification will not be delivered.

* PTRACE_ATTACH is not working because non-fatal signal delivery
is blocked in frozen state.

There are some interface differences between cgroup v1 and cgroup v2
freezer too, which are required to conform the cgroup v2 interface
design principles:
1) There is no separate controller, which has to be turned on:
the functionality is always available and is represented by
cgroup.freeze and cgroup.events cgroup control files.
2) The desired state is defined by the cgroup.freeze control file.
Any hierarchical configuration is allowed.
3) The interface is asynchronous. The actual state is available
using cgroup.events control file ("frozen" field). There are no
dedicated transitional states.
4) It's allowed to make any changes with the cgroup hierarchy
(create new cgroups, remove old cgroups, move tasks between cgroups)
no matter if some cgroups are frozen.

Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
No-objection-from-me-by: Oleg Nesterov <oleg@redhat.com>
Cc: kernel-team@fb.com
cgroup/pids: turn cgroup_subsys->free() into cgroup_subsys->release() to fix the accounting 2019-01-31T14:55:57+00:00 Oleg Nesterov oleg@redhat.com 2019-01-28T16:00:13+00:00 51bee5abeab2058ea5813c5615d6197a23dbf041 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> 
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>
blkcg: remove additional reference to the css 2018-12-08T05:26:37+00:00 Dennis Zhou dennis@kernel.org 2018-12-05T17:10:36+00:00 fc5a828bfad628c1092194f2814604943561c52d The previous patch in this series removed carrying around a pointer to the css in blkg. However, the blkg association logic still relied on taking a reference on the css to ensure we wouldn't fail in getting a reference for the blkg. Here the implicit dependency on the css is removed. The association continues to rely on the tryget logic walking up the blkg tree. This streamlines the three ways that association can happen: normal, swap, and writeback. Signed-off-by: Dennis Zhou <dennis@kernel.org> Acked-by: Tejun Heo <tj@kernel.org> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> 
The previous patch in this series removed carrying around a pointer to
the css in blkg. However, the blkg association logic still relied on
taking a reference on the css to ensure we wouldn't fail in getting a
reference for the blkg.

Here the implicit dependency on the css is removed. The association
continues to rely on the tryget logic walking up the blkg tree. This
streamlines the three ways that association can happen: normal, swap,
and writeback.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Merge tag 'for-linus-20181102' of git://git.kernel.dk/linux-block 2018-11-02T18:25:48+00:00 Linus Torvalds torvalds@linux-foundation.org 2018-11-02T18:25:48+00:00 5f21585384a4a69b8bfdd2cae7e3648ae805f57d Pull block layer fixes from Jens Axboe: "The biggest part of this pull request is the revert of the blkcg cleanup series. It had one fix earlier for a stacked device issue, but another one was reported. Rather than play whack-a-mole with this, revert the entire series and try again for the next kernel release. Apart from that, only small fixes/changes. Summary: - Indentation fixup for mtip32xx (Colin Ian King) - The blkcg cleanup series revert (Dennis Zhou) - Two NVMe fixes. One fixing a regression in the nvme request initialization in this merge window, causing nvme-fc to not work. The other is a suspend/resume p2p resource issue (James, Keith) - Fix sg discard merge, allowing us to merge in cases where we didn't before (Jianchao Wang) - Call rq_qos_exit() after the queue is frozen, preventing a hang (Ming) - Fix brd queue setup, fixing an oops if we fail setting up all devices (Ming)" * tag 'for-linus-20181102' of git://git.kernel.dk/linux-block: nvme-pci: fix conflicting p2p resource adds nvme-fc: fix request private initialization blkcg: revert blkcg cleanups series block: brd: associate with queue until adding disk block: call rq_qos_exit() after queue is frozen mtip32xx: clean an indentation issue, remove extraneous tabs block: fix the DISCARD request merge 
Pull block layer fixes from Jens Axboe:
 "The biggest part of this pull request is the revert of the blkcg
  cleanup series. It had one fix earlier for a stacked device issue, but
  another one was reported. Rather than play whack-a-mole with this,
  revert the entire series and try again for the next kernel release.

  Apart from that, only small fixes/changes.

  Summary:

   - Indentation fixup for mtip32xx (Colin Ian King)

   - The blkcg cleanup series revert (Dennis Zhou)

   - Two NVMe fixes. One fixing a regression in the nvme request
     initialization in this merge window, causing nvme-fc to not work.
     The other is a suspend/resume p2p resource issue (James, Keith)

   - Fix sg discard merge, allowing us to merge in cases where we didn't
     before (Jianchao Wang)

   - Call rq_qos_exit() after the queue is frozen, preventing a hang
     (Ming)

   - Fix brd queue setup, fixing an oops if we fail setting up all
     devices (Ming)"

* tag 'for-linus-20181102' of git://git.kernel.dk/linux-block:
  nvme-pci: fix conflicting p2p resource adds
  nvme-fc: fix request private initialization
  blkcg: revert blkcg cleanups series
  block: brd: associate with queue until adding disk
  block: call rq_qos_exit() after queue is frozen
  mtip32xx: clean an indentation issue, remove extraneous tabs
  block: fix the DISCARD request merge
blkcg: revert blkcg cleanups series 2018-11-02T01:59:53+00:00 Dennis Zhou dennis@kernel.org 2018-11-01T21:24:10+00:00 b5f2954d30c77649bce9c27e7a0a94299d9cfdf8 This reverts a series committed earlier due to null pointer exception bug report in [1]. It seems there are edge case interactions that I did not consider and will need some time to understand what causes the adverse interactions. The original series can be found in [2] with a follow up series in [3]. [1] https://www.spinics.net/lists/cgroups/msg20719.html [2] https://lore.kernel.org/lkml/20180911184137.35897-1-dennisszhou@gmail.com/ [3] https://lore.kernel.org/lkml/20181020185612.51587-1-dennis@kernel.org/ This reverts the following commits: d459d853c2ed, b2c3fa546705, 101246ec02b5, b3b9f24f5fcc, e2b0989954ae, f0fcb3ec89f3, c839e7a03f92, bdc2491708c4, 74b7c02a9bc1, 5bf9a1f3b4ef, a7b39b4e961c, 07b05bcc3213, 49f4c2dc2b50, 27e6fa996c53 Signed-off-by: Dennis Zhou <dennis@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk> 
This reverts a series committed earlier due to null pointer exception
bug report in [1]. It seems there are edge case interactions that I did
not consider and will need some time to understand what causes the
adverse interactions.

The original series can be found in [2] with a follow up series in [3].

[1] https://www.spinics.net/lists/cgroups/msg20719.html
[2] https://lore.kernel.org/lkml/20180911184137.35897-1-dennisszhou@gmail.com/
[3] https://lore.kernel.org/lkml/20181020185612.51587-1-dennis@kernel.org/

This reverts the following commits:
d459d853c2ed, b2c3fa546705, 101246ec02b5, b3b9f24f5fcc, e2b0989954ae,
f0fcb3ec89f3, c839e7a03f92, bdc2491708c4, 74b7c02a9bc1, 5bf9a1f3b4ef,
a7b39b4e961c, 07b05bcc3213, 49f4c2dc2b50, 27e6fa996c53

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
psi: cgroup support 2018-10-26T23:26:32+00:00 Johannes Weiner hannes@cmpxchg.org 2018-10-26T22:06:31+00:00 2ce7135adc9ad081aa3c49744144376ac74fea60 On a system that executes multiple cgrouped jobs and independent workloads, we don't just care about the health of the overall system, but also that of individual jobs, so that we can ensure individual job health, fairness between jobs, or prioritize some jobs over others. This patch implements pressure stall tracking for cgroups. In kernels with CONFIG_PSI=y, cgroup2 groups will have cpu.pressure, memory.pressure, and io.pressure files that track aggregate pressure stall times for only the tasks inside the cgroup. Link: http://lkml.kernel.org/r/20180828172258.3185-10-hannes@cmpxchg.org Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Tejun Heo <tj@kernel.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Daniel Drake <drake@endlessm.com> Tested-by: Suren Baghdasaryan <surenb@google.com> Cc: Christopher Lameter <cl@linux.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Johannes Weiner <jweiner@fb.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Enderborg <peter.enderborg@sony.com> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Shakeel Butt <shakeelb@google.com> Cc: Vinayak Menon <vinmenon@codeaurora.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
On a system that executes multiple cgrouped jobs and independent
workloads, we don't just care about the health of the overall system, but
also that of individual jobs, so that we can ensure individual job health,
fairness between jobs, or prioritize some jobs over others.

This patch implements pressure stall tracking for cgroups.  In kernels
with CONFIG_PSI=y, cgroup2 groups will have cpu.pressure, memory.pressure,
and io.pressure files that track aggregate pressure stall times for only
the tasks inside the cgroup.

Link: http://lkml.kernel.org/r/20180828172258.3185-10-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Daniel Drake <drake@endlessm.com>
Tested-by: Suren Baghdasaryan <surenb@google.com>
Cc: Christopher Lameter <cl@linux.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <jweiner@fb.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Enderborg <peter.enderborg@sony.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Vinayak Menon <vinmenon@codeaurora.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Merge branch 'for-4.20' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2018-10-26T00:15:46+00:00 Linus Torvalds torvalds@linux-foundation.org 2018-10-26T00:15:46+00:00 83c4087ce468601501ecde4d0ec5b2abd5f57c31 Pull cgroup updates from Tejun Heo: "All trivial changes - simplification, typo fix and adding cond_resched() in a netclassid update loop" * 'for-4.20' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: cgroup, netclassid: add a preemption point to write_classid rdmacg: fix a typo in rdmacg documentation cgroup: Simplify cgroup_ancestor 
Pull cgroup updates from Tejun Heo:
 "All trivial changes - simplification, typo fix and adding
  cond_resched() in a netclassid update loop"

* 'for-4.20' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup, netclassid: add a preemption point to write_classid
  rdmacg: fix a typo in rdmacg documentation
  cgroup: Simplify cgroup_ancestor
cgroup: Simplify cgroup_ancestor 2018-09-24T17:38:16+00:00 Andrey Ignatov rdna@fb.com 2018-09-22T00:03:27+00:00 808c43b7c7f70360ed7b9e43e2cf980f388e71fa Simplify cgroup_ancestor function. This is follow-up for commit 7723628101aa ("bpf: Introduce bpf_skb_ancestor_cgroup_id helper") Suggested-by: Tejun Heo <tj@kernel.org> Signed-off-by: Andrey Ignatov <rdna@fb.com> Signed-off-by: Tejun Heo <tj@kernel.org> 
Simplify cgroup_ancestor function. This is follow-up for
commit 7723628101aa ("bpf: Introduce bpf_skb_ancestor_cgroup_id helper")

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
blkcg: remove additional reference to the css 2018-09-22T02:29:15+00:00 Dennis Zhou (Facebook) dennisszhou@gmail.com 2018-09-11T18:41:34+00:00 f0fcb3ec89f37167810e660b0595d9a6155d9807 The previous patch in this series removed carrying around a pointer to the css in blkg. However, the blkg association logic still relied on taking a reference on the css to ensure we wouldn't fail in getting a reference for the blkg. Here the implicit dependency on the css is removed. The association continues to rely on the tryget logic walking up the blkg tree. This streamlines the three ways that association can happen: normal, swap, and writeback. Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Dennis Zhou <dennisszhou@gmail.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> 
The previous patch in this series removed carrying around a pointer to
the css in blkg. However, the blkg association logic still relied on
taking a reference on the css to ensure we wouldn't fail in getting a
reference for the blkg.

Here the implicit dependency on the css is removed. The association
continues to rely on the tryget logic walking up the blkg tree. This
streamlines the three ways that association can happen: normal, swap,
and writeback.

Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Dennis Zhou <dennisszhou@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>