It is possible for a reclaimer to cause demotions of an lruvec belonging
to a cgroup with cpuset.mems set to exclude some nodes. Attempt to apply
this limitation based on the lruvec's memcg and prevent demotion.
Notably, this may still allow demotion of shared libraries or any memory
first instantiated in another cgroup. This means cpusets still cannot
cannot guarantee complete isolation when demotion is enabled, and the docs
have been updated to reflect this.
This is useful for isolating workloads on a multi-tenant system from
certain classes of memory more consistently - with the noted exceptions.
Note on locking:
The cgroup_get_e_css reference protects the css->effective_mems, and calls
of this interface would be subject to the same race conditions associated
with a non-atomic access to cs->effective_mems.
So while this interface cannot make strong guarantees of correctness, it
can therefore avoid taking a global or rcu_read_lock for performance.
Link: https://lkml.kernel.org/r/20250424202806.52632-3-gourry@gourry.net
Signed-off-by: Gregory Price <gourry@gourry.net>
Suggested-by: Shakeel Butt <shakeel.butt@linux.dev>
Suggested-by: Waiman Long <longman@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev>
Reviewed-by: Waiman Long <longman@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "vmscan: enforce mems_effective during demotion", v5.
Change reclaim to respect cpuset.mems_effective during demotion when
possible. Presently, reclaim explicitly ignores cpuset.mems_effective
when demoting, which may cause the cpuset settings to violated.
Implement cpuset_node_allowed() to check the cpuset.mems_effective
associated wih the mem_cgroup of the lruvec being scanned. This only
applies to cgroup/cpuset v2, as cpuset exists in a different hierarchy
than mem_cgroup in v1.
This requires renaming the existing cpuset_node_allowed() to be
cpuset_current_now_allowed() - which is more descriptive anyway - to
implement the new cpuset_node_allowed() which takes a target cgroup.
This patch (of 2):
Rename cpuset_node_allowed to reflect that the function checks the current
task's cpuset.mems. This allows us to make a new cpuset_node_allowed
function that checks a target cgroup's cpuset.mems.
Link: https://lkml.kernel.org/r/20250424202806.52632-1-gourry@gourry.net
Link: https://lkml.kernel.org/r/20250424202806.52632-2-gourry@gourry.net
Signed-off-by: Gregory Price <gourry@gourry.net>
Acked-by: Waiman Long <longman@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Rebuilding of root domains accounting information (total_bw) is
currently broken on some cases, e.g. suspend/resume on aarch64. Problem
is that the way we keep track of domain changes and try to add bandwidth
back is convoluted and fragile.
Fix it by simplify things by making sure bandwidth accounting is cleared
and completely restored after root domains changes (after root domains
are again stable).
To be sure we always call dl_rebuild_rd_accounting while holding
cpuset_mutex we also add cpuset_reset_sched_domains() wrapper.
Fixes: 53916d5fd3 ("sched/deadline: Check bandwidth overflow earlier for hotplug")
Reported-by: Jon Hunter <jonathanh@nvidia.com>
Co-developed-by: Waiman Long <llong@redhat.com>
Signed-off-by: Waiman Long <llong@redhat.com>
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lore.kernel.org/r/Z9MRfeJKJUOyUSto@jlelli-thinkpadt14gen4.remote.csb
This patch introduces CONFIG_CPUSETS_V1 and guard cpuset-v1 code under
CONFIG_CPUSETS_V1. The default value of CONFIG_CPUSETS_V1 is N, so that
user who adopted v2 don't have 'pay' for cpuset v1.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Since the SLAB implementation was removed in v6.8, so the
cpuset_slab_spread_rotor is no longer used and can be removed.
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Since commit 3a5a6d0c2b03("cpuset: don't nest cgroup_mutex inside
get_online_cpus()"), cpuset hotplug was done asynchronously via a work
function. This is to avoid recursive locking of cgroup_mutex.
Since then, the cgroup locking scheme has changed quite a bit. A
cpuset_mutex was introduced to protect cpuset specific operations.
The cpuset_mutex is then replaced by a cpuset_rwsem. With commit
d74b27d63a ("cgroup/cpuset: Change cpuset_rwsem and hotplug lock
order"), cpu_hotplug_lock is acquired before cpuset_rwsem. Later on,
cpuset_rwsem is reverted back to cpuset_mutex. All these locking changes
allow the hotplug code to call into cpuset core directly.
The following commits were also merged due to the asynchronous nature
of cpuset hotplug processing.
- commit b22afcdf04 ("cpu/hotplug: Cure the cpusets trainwreck")
- commit 50e7663233 ("sched/cpuset/pm: Fix cpuset vs. suspend-resume
bugs")
- commit 28b89b9e6f ("cpuset: handle race between CPU hotplug and
cpuset_hotplug_work")
Clean up all these bandages by making cpuset hotplug
processing synchronous again with the exception that the call to
cgroup_transfer_tasks() to transfer tasks out of an empty cgroup v1
cpuset, if necessary, will still be done via a work function due to the
existing cgroup_mutex -> cpu_hotplug_lock dependency. It is possible
to reverse that dependency, but that will require updating a number of
different cgroup controllers. This special hotplug code path should be
rarely taken anyway.
As all the cpuset states will be updated by the end of the hotplug
operation, we can revert most the above commits except commit
50e7663233 ("sched/cpuset/pm: Fix cpuset vs. suspend-resume bugs")
which is partially reverted. Also removing some cpus_read_lock trylock
attempts in the cpuset partition code as they are no longer necessary
since the cpu_hotplug_lock is now held for the whole duration of the
cpuset hotplug code path.
Signed-off-by: Waiman Long <longman@redhat.com>
Tested-by: Valentin Schneider <vschneid@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Currently, the cpu_is_isolated() function checks only the statically
isolated CPUs specified via the "isolcpus" and "nohz_full" kernel
command line options. This function is used by vmstat and memcg to
reduce interference with isolated CPUs by not doing stat flushing
or scheduling works on those CPUs.
Workloads running on isolated CPUs within isolated cpuset
partitions should receive the same treatment to reduce unnecessary
interference. This patch introduces a new cpuset_cpu_is_isolated()
function to be called by cpu_is_isolated() so that the set of dynamically
created cpuset isolated CPUs will be included in the check.
Assuming that testing a bit in a cpumask is atomic, no synchronization
primitive is currently used to synchronize access to the cpuset's
isolated_cpus mask.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Qais reported that iterating over all tasks when rebuilding root domains
for finding out which ones are DEADLINE and need their bandwidth
correctly restored on such root domains can be a costly operation (10+
ms delays on suspend-resume).
To fix the problem keep track of the number of DEADLINE tasks belonging
to each cpuset and then use this information (followup patch) to only
perform the above iteration if DEADLINE tasks are actually present in
the cpuset for which a corresponding root domain is being rebuilt.
Reported-by: Qais Yousef <qyousef@layalina.io>
Link: https://lore.kernel.org/lkml/20230206221428.2125324-1-qyousef@layalina.io/
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Turns out percpu_cpuset_rwsem - commit 1243dc518c ("cgroup/cpuset:
Convert cpuset_mutex to percpu_rwsem") - wasn't such a brilliant idea,
as it has been reported to cause slowdowns in workloads that need to
change cpuset configuration frequently and it is also not implementing
priority inheritance (which causes troubles with realtime workloads).
Convert percpu_cpuset_rwsem back to regular cpuset_mutex. Also grab it
only for SCHED_DEADLINE tasks (other policies don't care about stable
cpusets anyway).
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Commit 002f290627 ("cpuset: use static key better and convert to new API")
has used __cpuset_node_allowed() instead of cpuset_node_allowed() to check
whether we can allocate on a memory node. Now this function isn't used by
anyone, so we can do the follow things to clean up it.
1. remove unused codes
2. rename __cpuset_node_allowed() to cpuset_node_allowed()
3. update comments in mm/page_alloc.c
Suggested-by: Waiman Long <longman@redhat.com>
Signed-off-by: Haifeng Xu <haifeng.xu@shopee.com>
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
There was a report that starting an Ubuntu in docker while using cpuset
to bind it to movable nodes (a node only has movable zone, like a node
for hotplug or a Persistent Memory node in normal usage) will fail due
to memory allocation failure, and then OOM is involved and many other
innocent processes got killed.
It can be reproduced with command:
$ docker run -it --rm --cpuset-mems 4 ubuntu:latest bash -c "grep Mems_allowed /proc/self/status"
(where node 4 is a movable node)
runc:[2:INIT] invoked oom-killer: gfp_mask=0x500cc2(GFP_HIGHUSER|__GFP_ACCOUNT), order=0, oom_score_adj=0
CPU: 8 PID: 8291 Comm: runc:[2:INIT] Tainted: G W I E 5.8.2-0.g71b519a-default #1 openSUSE Tumbleweed (unreleased)
Hardware name: Dell Inc. PowerEdge R640/0PHYDR, BIOS 2.6.4 04/09/2020
Call Trace:
dump_stack+0x6b/0x88
dump_header+0x4a/0x1e2
oom_kill_process.cold+0xb/0x10
out_of_memory.part.0+0xaf/0x230
out_of_memory+0x3d/0x80
__alloc_pages_slowpath.constprop.0+0x954/0xa20
__alloc_pages_nodemask+0x2d3/0x300
pipe_write+0x322/0x590
new_sync_write+0x196/0x1b0
vfs_write+0x1c3/0x1f0
ksys_write+0xa7/0xe0
do_syscall_64+0x52/0xd0
entry_SYSCALL_64_after_hwframe+0x44/0xa9
Mem-Info:
active_anon:392832 inactive_anon:182 isolated_anon:0
active_file:68130 inactive_file:151527 isolated_file:0
unevictable:2701 dirty:0 writeback:7
slab_reclaimable:51418 slab_unreclaimable:116300
mapped:45825 shmem:735 pagetables:2540 bounce:0
free:159849484 free_pcp:73 free_cma:0
Node 4 active_anon:1448kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB mapped:0kB dirty:0kB writeback:0kB shmem:0kB shmem_thp: 0kB shmem_pmdmapped: 0kB anon_thp: 0kB writeback_tmp:0kB all_unreclaimable? no
Node 4 Movable free:130021408kB min:9140kB low:139160kB high:269180kB reserved_highatomic:0KB active_anon:1448kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:130023424kB managed:130023424kB mlocked:0kB kernel_stack:0kB pagetables:0kB bounce:0kB free_pcp:292kB local_pcp:84kB free_cma:0kB
lowmem_reserve[]: 0 0 0 0 0
Node 4 Movable: 1*4kB (M) 0*8kB 0*16kB 1*32kB (M) 0*64kB 0*128kB 1*256kB (M) 1*512kB (M) 1*1024kB (M) 0*2048kB 31743*4096kB (M) = 130021156kB
oom-kill:constraint=CONSTRAINT_CPUSET,nodemask=(null),cpuset=docker-9976a269caec812c134fa317f27487ee36e1129beba7278a463dd53e5fb9997b.scope,mems_allowed=4,global_oom,task_memcg=/system.slice/containerd.service,task=containerd,pid=4100,uid=0
Out of memory: Killed process 4100 (containerd) total-vm:4077036kB, anon-rss:51184kB, file-rss:26016kB, shmem-rss:0kB, UID:0 pgtables:676kB oom_score_adj:0
oom_reaper: reaped process 8248 (docker), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB
oom_reaper: reaped process 2054 (node_exporter), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB
oom_reaper: reaped process 1452 (systemd-journal), now anon-rss:0kB, file-rss:8564kB, shmem-rss:4kB
oom_reaper: reaped process 2146 (munin-node), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB
oom_reaper: reaped process 8291 (runc:[2:INIT]), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB
The reason is that in this case, the target cpuset nodes only have
movable zone, while the creation of an OS in docker sometimes needs to
allocate memory in non-movable zones (dma/dma32/normal) like
GFP_HIGHUSER, and the cpuset limit forbids the allocation, then
out-of-memory killing is involved even when normal nodes and movable
nodes both have many free memory.
The OOM killer cannot help to resolve the situation as there is no
usable memory for the request in the cpuset scope. The only reasonable
measure to take is to fail the allocation right away and have the caller
to deal with it.
So add a check for cases like this in the slowpath of allocation, and
bail out early returning NULL for the allocation.
As page allocation is one of the hottest path in kernel, this check will
hurt all users with sane cpuset configuration, add a static branch check
and detect the abnormal config in cpuset memory binding setup so that
the extra check cost in page allocation is not paid by everyone.
[thanks to Micho Hocko and David Rientjes for suggesting not handling
it inside OOM code, adding cpuset check, refining comments]
Link: https://lkml.kernel.org/r/1632481657-68112-1-git-send-email-feng.tang@intel.com
Signed-off-by: Feng Tang <feng.tang@intel.com>
Suggested-by: Michal Hocko <mhocko@suse.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Zefan Li <lizefan.x@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
select_fallback_rq() only needs to recheck for an allowed CPU if the
affinity mask of the task has changed since the last check.
Return a 'bool' from cpuset_cpus_allowed_fallback() to indicate whether
the affinity mask was updated, and use this to elide the allowed check
when the mask has been left alone.
No functional change.
Suggested-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lore.kernel.org/r/20210730112443.23245-5-will@kernel.org
Asymmetric systems may not offer the same level of userspace ISA support
across all CPUs, meaning that some applications cannot be executed by
some CPUs. As a concrete example, upcoming arm64 big.LITTLE designs do
not feature support for 32-bit applications on both clusters.
Modify guarantee_online_cpus() to take task_cpu_possible_mask() into
account when trying to find a suitable set of online CPUs for a given
task. This will avoid passing an invalid mask to set_cpus_allowed_ptr()
during ->attach() and will subsequently allow the cpuset hierarchy to be
taken into account when forcefully overriding the affinity mask for a
task which requires migration to a compatible CPU.
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <Valentin.Schneider@arm.com>
Link: https://lkml.kernel.org/r/20210730112443.23245-4-will@kernel.org
If the scheduler cannot find an allowed CPU for a task,
cpuset_cpus_allowed_fallback() will widen the affinity to cpu_possible_mask
if cgroup v1 is in use.
In preparation for allowing architectures to provide their own fallback
mask, just return early if we're either using cgroup v1 or we're using
cgroup v2 with a mask that contains invalid CPUs. This will allow
select_fallback_rq() to figure out the mask by itself.
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Quentin Perret <qperret@google.com>
Link: https://lkml.kernel.org/r/20210730112443.23245-3-will@kernel.org
Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.
By default all files without license information are under the default
license of the kernel, which is GPL version 2.
Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.
This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.
How this work was done:
Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,
Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.
The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.
The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.
Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).
All documentation files were explicitly excluded.
The following heuristics were used to determine which SPDX license
identifiers to apply.
- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.
For non */uapi/* files that summary was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139
and resulted in the first patch in this series.
If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930
and resulted in the second patch in this series.
- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:
SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1
and that resulted in the third patch in this series.
- when the two scanners agreed on the detected license(s), that became
the concluded license(s).
- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.
- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).
- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.
- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.
In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.
Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.
Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.
In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.
Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct
This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.
These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cpusets vs. suspend-resume is _completely_ broken. And it got noticed
because it now resulted in non-cpuset usage breaking too.
On suspend cpuset_cpu_inactive() doesn't call into
cpuset_update_active_cpus() because it doesn't want to move tasks about,
there is no need, all tasks are frozen and won't run again until after
we've resumed everything.
But this means that when we finally do call into
cpuset_update_active_cpus() after resuming the last frozen cpu in
cpuset_cpu_active(), the top_cpuset will not have any difference with
the cpu_active_mask and this it will not in fact do _anything_.
So the cpuset configuration will not be restored. This was largely
hidden because we would unconditionally create identity domains and
mobile users would not in fact use cpusets much. And servers what do use
cpusets tend to not suspend-resume much.
An addition problem is that we'd not in fact wait for the cpuset work to
finish before resuming the tasks, allowing spurious migrations outside
of the specified domains.
Fix the rebuild by introducing cpuset_force_rebuild() and fix the
ordering with cpuset_wait_for_hotplug().
Reported-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: deb7aa308e ("cpuset: reorganize CPU / memory hotplug handling")
Link: http://lkml.kernel.org/r/20170907091338.orwxrqkbfkki3c24@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
In codepaths that use the begin/retry interface for reading
mems_allowed_seq with irqs disabled, there exists a race condition that
stalls the patch process after only modifying a subset of the
static_branch call sites.
This problem manifested itself as a deadlock in the slub allocator,
inside get_any_partial. The loop reads mems_allowed_seq value (via
read_mems_allowed_begin), performs the defrag operation, and then
verifies the consistency of mem_allowed via the read_mems_allowed_retry
and the cookie returned by xxx_begin.
The issue here is that both begin and retry first check if cpusets are
enabled via cpusets_enabled() static branch. This branch can be
rewritted dynamically (via cpuset_inc) if a new cpuset is created. The
x86 jump label code fully synchronizes across all CPUs for every entry
it rewrites. If it rewrites only one of the callsites (specifically the
one in read_mems_allowed_retry) and then waits for the
smp_call_function(do_sync_core) to complete while a CPU is inside the
begin/retry section with IRQs off and the mems_allowed value is changed,
we can hang.
This is because begin() will always return 0 (since it wasn't patched
yet) while retry() will test the 0 against the actual value of the seq
counter.
The fix is to use two different static keys: one for begin
(pre_enable_key) and one for retry (enable_key). In cpuset_inc(), we
first bump the pre_enable key to ensure that cpuset_mems_allowed_begin()
always return a valid seqcount if are enabling cpusets. Similarly, when
disabling cpusets via cpuset_dec(), we first ensure that callers of
cpuset_mems_allowed_retry() will start ignoring the seqcount value
before we let cpuset_mems_allowed_begin() return 0.
The relevant stack traces of the two stuck threads:
CPU: 1 PID: 1415 Comm: mkdir Tainted: G L 4.9.36-00104-g540c51286237 #4
Hardware name: Default string Default string/Hardware, BIOS 4.29.1-20170526215256 05/26/2017
task: ffff8817f9c28000 task.stack: ffffc9000ffa4000
RIP: smp_call_function_many+0x1f9/0x260
Call Trace:
smp_call_function+0x3b/0x70
on_each_cpu+0x2f/0x90
text_poke_bp+0x87/0xd0
arch_jump_label_transform+0x93/0x100
__jump_label_update+0x77/0x90
jump_label_update+0xaa/0xc0
static_key_slow_inc+0x9e/0xb0
cpuset_css_online+0x70/0x2e0
online_css+0x2c/0xa0
cgroup_apply_control_enable+0x27f/0x3d0
cgroup_mkdir+0x2b7/0x420
kernfs_iop_mkdir+0x5a/0x80
vfs_mkdir+0xf6/0x1a0
SyS_mkdir+0xb7/0xe0
entry_SYSCALL_64_fastpath+0x18/0xad
...
CPU: 2 PID: 1 Comm: init Tainted: G L 4.9.36-00104-g540c51286237 #4
Hardware name: Default string Default string/Hardware, BIOS 4.29.1-20170526215256 05/26/2017
task: ffff8818087c0000 task.stack: ffffc90000030000
RIP: int3+0x39/0x70
Call Trace:
<#DB> ? ___slab_alloc+0x28b/0x5a0
<EOE> ? copy_process.part.40+0xf7/0x1de0
__slab_alloc.isra.80+0x54/0x90
copy_process.part.40+0xf7/0x1de0
copy_process.part.40+0xf7/0x1de0
kmem_cache_alloc_node+0x8a/0x280
copy_process.part.40+0xf7/0x1de0
_do_fork+0xe7/0x6c0
_raw_spin_unlock_irq+0x2d/0x60
trace_hardirqs_on_caller+0x136/0x1d0
entry_SYSCALL_64_fastpath+0x5/0xad
do_syscall_64+0x27/0x350
SyS_clone+0x19/0x20
do_syscall_64+0x60/0x350
entry_SYSCALL64_slow_path+0x25/0x25
Link: http://lkml.kernel.org/r/20170731040113.14197-1-dmitriyz@waymo.com
Fixes: 46e700abc4 ("mm, page_alloc: remove unnecessary taking of a seqlock when cpusets are disabled")
Signed-off-by: Dima Zavin <dmitriyz@waymo.com>
Reported-by: Cliff Spradlin <cspradlin@waymo.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Christopher Lameter <cl@linux.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Gregory Price
Juri Lelli
Chen Ridong
Xiu Jianfeng
Waiman Long
Xiongwei Song
Haifeng Xu
Feng Tang
Will Deacon
Yaowei Bai
Greg Kroah-Hartman
Peter Zijlstra
Paolo Bonzini
Dima Zavin
Rakib Mullick
Ingo Molnar