kernel/linux.git/include/linux/cgroup.h, branch v6.19.11

cgroup: Defer task cgroup unlink until after the task is done switching out

2025-11-03T21:46:18+00:00

When a task exits, css_set_move_task(tsk, cset, NULL, false) unlinks the task from its cgroup. From the cgroup's perspective, the task is now gone. If this makes the cgroup empty, it can be removed, triggering ->css_offline() callbacks that notify controllers the cgroup is going offline resource-wise. However, the exiting task can still run, perform memory operations, and schedule until the final context switch in finish_task_switch(). This creates a confusing situation where controllers are told a cgroup is offline while resource activities are still happening in it. While this hasn't broken existing controllers, it has caused direct confusion for sched_ext schedulers. Split cgroup_task_exit() into two functions. cgroup_task_exit() now only calls the subsystem exit callbacks and continues to be called from do_exit(). The css_set cleanup is moved to the new cgroup_task_dead() which is called from finish_task_switch() after the final context switch, so that the cgroup only appears empty after the task is truly done running. This also reorders operations so that subsys->exit() is now called before unlinking from the cgroup, which shouldn't break anything. Cc: Dan Schatzberg Cc: Peter Zijlstra Signed-off-by: Tejun Heo

cgroup: Rename cgroup lifecycle hooks to cgroup_task_*()

2025-11-03T21:46:18+00:00

The current names cgroup_exit(), cgroup_release(), and cgroup_free() are confusing because they look like they're operating on cgroups themselves when they're actually task lifecycle hooks. For example, cgroup_init() initializes the cgroup subsystem while cgroup_exit() is a task exit notification to cgroup. Rename them to cgroup_task_exit(), cgroup_task_release(), and cgroup_task_free() to make it clear that these operate on tasks. Cc: Dan Schatzberg Cc: Peter Zijlstra Reviewed-by: Chen Ridong Signed-off-by: Tejun Heo

Merge tag 'bpf-next-6.18' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next

2025-10-01T00:58:11+00:00

Pull bpf updates from Alexei Starovoitov: - Support pulling non-linear xdp data with bpf_xdp_pull_data() kfunc (Amery Hung) Applied as a stable branch in bpf-next and net-next trees. - Support reading skb metadata via bpf_dynptr (Jakub Sitnicki) Also a stable branch in bpf-next and net-next trees. - Enforce expected_attach_type for tailcall compatibility (Daniel Borkmann) - Replace path-sensitive with path-insensitive live stack analysis in the verifier (Eduard Zingerman) This is a significant change in the verification logic. More details, motivation, long term plans are in the cover letter/merge commit. - Support signed BPF programs (KP Singh) This is another major feature that took years to materialize. Algorithm details are in the cover letter/marge commit - Add support for may_goto instruction to s390 JIT (Ilya Leoshkevich) - Add support for may_goto instruction to arm64 JIT (Puranjay Mohan) - Fix USDT SIB argument handling in libbpf (Jiawei Zhao) - Allow uprobe-bpf program to change context registers (Jiri Olsa) - Support signed loads from BPF arena (Kumar Kartikeya Dwivedi and Puranjay Mohan) - Allow access to union arguments in tracing programs (Leon Hwang) - Optimize rcu_read_lock() + migrate_disable() combination where it's used in BPF subsystem (Menglong Dong) - Introduce bpf_task_work_schedule*() kfuncs to schedule deferred execution of BPF callback in the context of a specific task using the kernel’s task_work infrastructure (Mykyta Yatsenko) - Enforce RCU protection for KF_RCU_PROTECTED kfuncs (Kumar Kartikeya Dwivedi) - Add stress test for rqspinlock in NMI (Kumar Kartikeya Dwivedi) - Improve the precision of tnum multiplier verifier operation (Nandakumar Edamana) - Use tnums to improve is_branch_taken() logic (Paul Chaignon) - Add support for atomic operations in arena in riscv JIT (Pu Lehui) - Report arena faults to BPF error stream (Puranjay Mohan) - Search for tracefs at /sys/kernel/tracing first in bpftool (Quentin Monnet) - Add bpf_strcasecmp() kfunc (Rong Tao) - Support lookup_and_delete_elem command in BPF_MAP_STACK_TRACE (Tao Chen) * tag 'bpf-next-6.18' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (197 commits) libbpf: Replace AF_ALG with open coded SHA-256 selftests/bpf: Add stress test for rqspinlock in NMI selftests/bpf: Add test case for different expected_attach_type bpf: Enforce expected_attach_type for tailcall compatibility bpftool: Remove duplicate string.h header bpf: Remove duplicate crypto/sha2.h header libbpf: Fix error when st-prefix_ops and ops from differ btf selftests/bpf: Test changing packet data from kfunc selftests/bpf: Add stacktrace map lookup_and_delete_elem test case selftests/bpf: Refactor stacktrace_map case with skeleton bpf: Add lookup_and_delete_elem for BPF_MAP_STACK_TRACE selftests/bpf: Fix flaky bpf_cookie selftest selftests/bpf: Test changing packet data from global functions with a kfunc bpf: Emit struct bpf_xdp_sock type in vmlinux BTF selftests/bpf: Task_work selftest cleanup fixes MAINTAINERS: Delete inactive maintainers from AF_XDP bpf: Mark kfuncs as __noclone selftests/bpf: Add kprobe multi write ctx attach test selftests/bpf: Add kprobe write ctx attach test selftests/bpf: Add uprobe context ip register change test ...

Merge tag 'cgroup-for-6.18' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

2025-09-30T16:55:41+00:00

Pull cgroup updates from Tejun Heo: - Extensive cpuset code cleanup and refactoring work with no functional changes: CPU mask computation logic refactoring, introducing new helpers, removing redundant code paths, and improving error handling for better maintainability. - A few bug fixes to cpuset including fixes for partition creation failures when isolcpus is in use, missing error returns, and null pointer access prevention in free_tmpmasks(). - Core cgroup changes include replacing the global percpu_rwsem with per-threadgroup rwsem when writing to cgroup.procs for better scalability, workqueue conversions to use WQ_PERCPU and system_percpu_wq to prepare for workqueue default switching from percpu to unbound, and removal of unused code including the post_attach callback. - New cgroup.stat.local time accounting feature that tracks frozen time duration. - Misc changes including selftests updates (new freezer time tests and backward compatibility fixes), documentation sync, string function safety improvements, and 64-bit division fixes. * tag 'cgroup-for-6.18' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (39 commits) cpuset: remove is_prs_invalid helper cpuset: remove impossible warning in update_parent_effective_cpumask cpuset: remove redundant special case for null input in node mask update cpuset: fix missing error return in update_cpumask cpuset: Use new excpus for nocpu error check when enabling root partition cpuset: fix failure to enable isolated partition when containing isolcpus Documentation: cgroup-v2: Sync manual toctree cpuset: use partition_cpus_change for setting exclusive cpus cpuset: use parse_cpulist for setting cpus.exclusive cpuset: introduce partition_cpus_change cpuset: refactor cpus_allowed_validate_change cpuset: refactor out validate_partition cpuset: introduce cpus_excl_conflict and mems_excl_conflict helpers cpuset: refactor CPU mask buffer parsing logic cpuset: Refactor exclusive CPU mask computation logic cpuset: change return type of is_partition_[in]valid to bool cpuset: remove unused assignment to trialcs->partition_root_state cpuset: move the root cpuset write check earlier cgroup/cpuset: Remove redundant rcu_read_lock/unlock() in spin_lock cgroup: Remove redundant rcu_read_lock/unlock() in spin_lock ...

Merge tag 'namespace-6.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2025-09-29T18:20:29+00:00

Pull namespace updates from Christian Brauner: "This contains a larger set of changes around the generic namespace infrastructure of the kernel. Each specific namespace type (net, cgroup, mnt, ...) embedds a struct ns_common which carries the reference count of the namespace and so on. We open-coded and cargo-culted so many quirks for each namespace type that it just wasn't scalable anymore. So given there's a bunch of new changes coming in that area I've started cleaning all of this up. The core change is to make it possible to correctly initialize every namespace uniformly and derive the correct initialization settings from the type of the namespace such as namespace operations, namespace type and so on. This leaves the new ns_common_init() function with a single parameter which is the specific namespace type which derives the correct parameters statically. This also means the compiler will yell as soon as someone does something remotely fishy. The ns_common_init() addition also allows us to remove ns_alloc_inum() and drops any special-casing of the initial network namespace in the network namespace initialization code that Linus complained about. Another part is reworking the reference counting. The reference counting was open-coded and copy-pasted for each namespace type even though they all followed the same rules. This also removes all open accesses to the reference count and makes it private and only uses a very small set of dedicated helpers to manipulate them just like we do for e.g., files. In addition this generalizes the mount namespace iteration infrastructure introduced a few cycles ago. As reminder, the vfs makes it possible to iterate sequentially and bidirectionally through all mount namespaces on the system or all mount namespaces that the caller holds privilege over. This allow userspace to iterate over all mounts in all mount namespaces using the listmount() and statmount() system call. Each mount namespace has a unique identifier for the lifetime of the systems that is exposed to userspace. The network namespace also has a unique identifier working exactly the same way. This extends the concept to all other namespace types. The new nstree type makes it possible to lookup namespaces purely by their identifier and to walk the namespace list sequentially and bidirectionally for all namespace types, allowing userspace to iterate through all namespaces. Looking up namespaces in the namespace tree works completely locklessly. This also means we can move the mount namespace onto the generic infrastructure and remove a bunch of code and members from struct mnt_namespace itself. There's a bunch of stuff coming on top of this in the future but for now this uses the generic namespace tree to extend a concept introduced first for pidfs a few cycles ago. For a while now we have supported pidfs file handles for pidfds. This has proven to be very useful. This extends the concept to cover namespaces as well. It is possible to encode and decode namespace file handles using the common name_to_handle_at() and open_by_handle_at() apis. As with pidfs file handles, namespace file handles are exhaustive, meaning it is not required to actually hold a reference to nsfs in able to decode aka open_by_handle_at() a namespace file handle. Instead the FD_NSFS_ROOT constant can be passed which will let the kernel grab a reference to the root of nsfs internally and thus decode the file handle. Namespaces file descriptors can already be derived from pidfds which means they aren't subject to overmount protection bugs. IOW, it's irrelevant if the caller would not have access to an appropriate /proc//ns/ directory as they could always just derive the namespace based on a pidfd already. It has the same advantage as pidfds. It's possible to reliably and for the lifetime of the system refer to a namespace without pinning any resources and to compare them trivially. Permission checking is kept simple. If the caller is located in the namespace the file handle refers to they are able to open it otherwise they must hold privilege over the owning namespace of the relevant namespace. The namespace file handle layout is exposed as uapi and has a stable and extensible format. For now it simply contains the namespace identifier, the namespace type, and the inode number. The stable format means that userspace may construct its own namespace file handles without going through name_to_handle_at() as they are already allowed for pidfs and cgroup file handles" * tag 'namespace-6.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (65 commits) ns: drop assert ns: move ns type into struct ns_common nstree: make struct ns_tree private ns: add ns_debug() ns: simplify ns_common_init() further cgroup: add missing ns_common include ns: use inode initializer for initial namespaces selftests/namespaces: verify initial namespace inode numbers ns: rename to __ns_ref nsfs: port to ns_ref_*() helpers net: port to ns_ref_*() helpers uts: port to ns_ref_*() helpers ipv4: use check_net() net: use check_net() net-sysfs: use check_net() user: port to ns_ref_*() helpers time: port to ns_ref_*() helpers pid: port to ns_ref_*() helpers ipc: port to ns_ref_*() helpers cgroup: port to ns_ref_*() helpers ...

cgroup: split namespace into separate header

2025-09-19T12:26:18+00:00

We have dedicated headers for all namespace types. Add one for the cgroup namespace as well. Now it's consistent for all namespace types and easy to figure out what to include. Acked-by: Tejun Heo Reviewed-by: Jan Kara Signed-off-by: Christian Brauner

ns: add to__ns() to respective headers

2025-09-19T12:26:16+00:00

Every namespace type has a container_of(ns, , ns) static inline function that is currently not exposed in the header. So we have a bunch of places that open-code it via container_of(). Move it to the headers so we can use it directly. Reviewed-by: Aleksa Sarai Signed-off-by: Christian Brauner

bpf: Do not limit bpf_cgroup_from_id to current's namespace

2025-09-15T17:53:15+00:00

The bpf_cgroup_from_id kfunc relies on cgroup_get_from_id to obtain the cgroup corresponding to a given cgroup ID. This helper can be called in a lot of contexts where the current thread can be random. A recent example was its use in sched_ext's ops.tick(), to obtain the root cgroup pointer. Since the current task can be whatever random user space task preempted by the timer tick, this makes the behavior of the helper unreliable. Refactor out __cgroup_get_from_id as the non-namespace aware version of cgroup_get_from_id, and change bpf_cgroup_from_id to make use of it. There is no compatibility breakage here, since changing the namespace against which the lookup is being done to the root cgroup namespace only permits a wider set of lookups to succeed now. The cgroup IDs across namespaces are globally unique, and thus don't need to be retranslated. Reported-by: Dan Schatzberg Signed-off-by: Kumar Kartikeya Dwivedi Acked-by: Tejun Heo Link: https://lore.kernel.org/r/20250915032618.1551762-2-memxor@gmail.com Signed-off-by: Alexei Starovoitov

copy_process: pass clone_flags as u64 across calltree

2025-09-01T13:31:34+00:00

With the introduction of clone3 in commit 7f192e3cd316 ("fork: add clone3") the effective bit width of clone_flags on all architectures was increased from 32-bit to 64-bit, with a new type of u64 for the flags. However, for most consumers of clone_flags the interface was not changed from the previous type of unsigned long. While this works fine as long as none of the new 64-bit flag bits (CLONE_CLEAR_SIGHAND and CLONE_INTO_CGROUP) are evaluated, this is still undesirable in terms of the principle of least surprise. Thus, this commit fixes all relevant interfaces of callees to sys_clone3/copy_process (excluding the architecture-specific copy_thread) to consistently pass clone_flags as u64, so that no truncation to 32-bit integers occurs on 32-bit architectures. Signed-off-by: Simon Schuster Link: https://lore.kernel.org/20250901-nios2-implement-clone3-v2-2-53fcf5577d57@siemens-energy.com Acked-by: David Hildenbrand Reviewed-by: Lorenzo Stoakes Reviewed-by: Arnd Bergmann Signed-off-by: Christian Brauner

cpuset: remove redundant CS_ONLINE flag

2025-08-13T18:14:20+00:00

The CS_ONLINE flag was introduced prior to the CSS_ONLINE flag in the cpuset subsystem. Currently, the flag setting sequence is as follows: 1. cpuset_css_online() sets CS_ONLINE 2. css->flags gets CSS_ONLINE set ... 3. cgroup->kill_css sets CSS_DYING 4. cpuset_css_offline() clears CS_ONLINE 5. css->flags clears CSS_ONLINE The is_cpuset_online() check currently occurs between steps 1 and 3. However, it would be equally safe to perform this check between steps 2 and 3, as CSS_ONLINE provides the same synchronization guarantee as CS_ONLINE. Since CS_ONLINE is redundant with CSS_ONLINE and provides no additional synchronization benefits, we can safely remove it to simplify the code. Signed-off-by: Chen Ridong Acked-by: Waiman Long Signed-off-by: Tejun Heo