- 16 10月, 2015 4 次提交
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由 Tejun Heo 提交于
pids controller is completely broken in that it uncharges when a task exits allowing zombies to escape resource control. With the recent updates, cgroup core now maintains cgroup association till task free and pids controller can be fixed by uncharging on free instead of exit. This patch adds cgroup_subsys->free() method and update pids controller to use it instead of ->exit() for uncharging. Signed-off-by: NTejun Heo <tj@kernel.org> Cc: Aleksa Sarai <cyphar@cyphar.com>
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由 Tejun Heo 提交于
cgroup_exit() is called when a task exits and disassociates the exiting task from its cgroups and half-attach it to the root cgroup. This is unnecessary and undesirable. No controller actually needs an exiting task to be disassociated with non-root cgroups. Both cpu and perf_event controllers update the association to the root cgroup from their exit callbacks just to keep consistent with the cgroup core behavior. Also, this disassociation makes it difficult to track resources held by zombies or determine where the zombies came from. Currently, pids controller is completely broken as it uncharges on exit and zombies always escape the resource restriction. With cgroup association being reset on exit, fixing it is pretty painful. There's no reason to reset cgroup membership on exit. The zombie can be removed from its css_set so that it doesn't show up on "cgroup.procs" and thus can't be migrated or interfere with cgroup removal. It can still pin and point to the css_set so that its cgroup membership is maintained. This patch makes cgroup core keep zombies associated with their cgroups at the time of exit. * Previous patches decoupled populated_cnt tracking from css_set lifetime, so a dying task can be simply unlinked from its css_set while pinning and pointing to the css_set. This keeps css_set association from task side alive while hiding it from "cgroup.procs" and populated_cnt tracking. The css_set reference is dropped when the task_struct is freed. * ->exit() callback no longer needs the css arguments as the associated css never changes once PF_EXITING is set. Removed. * cpu and perf_events controllers no longer need ->exit() callbacks. There's no reason to explicitly switch away on exit. The final schedule out is enough. The callbacks are removed. * On traditional hierarchies, nothing changes. "/proc/PID/cgroup" still reports "/" for all zombies. On the default hierarchy, "/proc/PID/cgroup" keeps reporting the cgroup that the task belonged to at the time of exit. If the cgroup gets removed before the task is reaped, " (deleted)" is appended. v2: Build brekage due to missing dummy cgroup_free() when !CONFIG_CGROUP fixed. Signed-off-by: NTejun Heo <tj@kernel.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
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由 Tejun Heo 提交于
css_sets are synchronized through css_set_rwsem but the locking scheme is kinda bizarre. The hot paths - fork and exit - have to write lock the rwsem making the rw part pointless; furthermore, many readers already hold cgroup_mutex. One of the readers is css task iteration. It read locks the rwsem over the entire duration of iteration. This leads to silly locking behavior. When cpuset tries to migrate processes of a cgroup to a different NUMA node, css_set_rwsem is held across the entire migration attempt which can take a long time locking out forking, exiting and other cgroup operations. This patch updates css task iteration so that it locks css_set_rwsem only while the iterator is being advanced. css task iteration involves two levels - css_set and task iteration. As css_sets in use are practically immutable, simply pinning the current one is enough for resuming iteration afterwards. Task iteration is tricky as tasks may leave their css_set while iteration is in progress. This is solved by keeping track of active iterators and advancing them if their next task leaves its css_set. v2: put_task_struct() in css_task_iter_next() moved outside css_set_rwsem. A later patch will add cgroup operations to task_struct free path which may grab the same lock and this avoids deadlock possibilities. css_set_move_task() updated to use list_for_each_entry_safe() when walking task_iters and advancing them. This is necessary as advancing an iter may remove it from the list. Signed-off-by: NTejun Heo <tj@kernel.org>
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由 Tejun Heo 提交于
Currently, cgroup->nr_populated counts whether the cgroup has any css_sets linked to it and the number of children which has non-zero ->nr_populated. This works because a css_set's refcnt converges with the number of tasks linked to it and thus there's no css_set linked to a cgroup if it doesn't have any live tasks. To help tracking resource usage of zombie tasks, putting the ref of css_set will be separated from disassociating the task from the css_set which means that a cgroup may have css_sets linked to it even when it doesn't have any live tasks. This patch updates cgroup->nr_populated so that for the cgroup itself it counts the number of css_sets which have tasks associated with them so that empty css_sets don't skew the populated test. Signed-off-by: NTejun Heo <tj@kernel.org>
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- 19 9月, 2015 3 次提交
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由 Tejun Heo 提交于
cgroup core handles creations and removals of cgroup interface files as described by cftypes. There are cases where the handle for a given file instance is necessary, for example, to generate a file modified event. Currently, this is handled by explicitly matching the callback method pointer and storing the file handle manually in cgroup_add_file(). While this simple approach works for cgroup core files, it can't for controller interface files. This patch generalizes cgroup interface file handle handling. struct cgroup_file is defined and each cftype can optionally tell cgroup core to store the file handle by setting ->file_offset. A file handle remains accessible as long as the containing css is accessible. Both "cgroup.procs" and "cgroup.events" are converted to use the new generic mechanism instead of hooking directly into cgroup_add_file(). Also, cgroup_file_notify() which takes a struct cgroup_file and generates a file modified event on it is added and replaces explicit kernfs_notify() invocations. This generalizes cgroup file handle handling and allows controllers to generate file modified notifications. Signed-off-by: NTejun Heo <tj@kernel.org> Cc: Li Zefan <lizefan@huawei.com> Cc: Johannes Weiner <hannes@cmpxchg.org>
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由 Tejun Heo 提交于
cftype->mode allows controllers to give arbitrary permissions to interface knobs. Except for "cgroup.event_control", the existing uses are spurious. * Some explicitly specify S_IRUGO | S_IWUSR even though that's the default. * "cpuset.memory_pressure" specifies S_IRUGO while also setting a write callback which returns -EACCES. All it needs to do is simply not setting a write callback. "cgroup.event_control" uses cftype->mode to make the file world-writable. It's a misdesigned interface and we don't want controllers to be tweaking interface file permissions in general. This patch removes cftype->mode and all its spurious uses and implements CFTYPE_WORLD_WRITABLE for "cgroup.event_control" which is marked as compatibility-only. Signed-off-by: NTejun Heo <tj@kernel.org> Cc: Li Zefan <lizefan@huawei.com> Cc: Johannes Weiner <hannes@cmpxchg.org>
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由 Tejun Heo 提交于
memcg already uses "memory.events" for event reporting and other controllers may need event reporting too. Let's standardize on "$SUBSYS.events" interface file for reporting events which don't happen too frequently and thus can share event notification. "cgroup.populated" is replaced with "populated" field in "cgroup.events" and documentation is updated accordingly. Signed-off-by: NTejun Heo <tj@kernel.org> Cc: Li Zefan <lizefan@huawei.com> Cc: Johannes Weiner <hannes@cmpxchg.org>
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- 18 9月, 2015 1 次提交
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由 Tejun Heo 提交于
Replace cgroup_subsys->disabled tests in controllers with cgroup_subsys_enabled(). cgroup_subsys_enabled() requires literal subsys name as its parameter and thus can't be used for cgroup core which iterates through controllers. For cgroup core, introduce and use cgroup_ssid_enabled() which uses slower static_key_enabled() test and can be indexed by subsys ID. This leaves cgroup_subsys->disabled unused. Removed. Signed-off-by: NTejun Heo <tj@kernel.org> Acked-by: NZefan Li <lizefan@huawei.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org>
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- 17 9月, 2015 1 次提交
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由 Tejun Heo 提交于
Note: This commit was originally committed as d59cfc09 but got reverted by 0c986253 due to the performance regression from the percpu_rwsem write down/up operations added to cgroup task migration path. percpu_rwsem changes which alleviate the performance issue are pending for v4.4-rc1 merge window. Re-apply. The cgroup side of threadgroup locking uses signal_struct->group_rwsem to synchronize against threadgroup changes. This per-process rwsem adds small overhead to thread creation, exit and exec paths, forces cgroup code paths to do lock-verify-unlock-retry dance in a couple places and makes it impossible to atomically perform operations across multiple processes. This patch replaces signal_struct->group_rwsem with a global percpu_rwsem cgroup_threadgroup_rwsem which is cheaper on the reader side and contained in cgroups proper. This patch converts one-to-one. This does make writer side heavier and lower the granularity; however, cgroup process migration is a fairly cold path, we do want to optimize thread operations over it and cgroup migration operations don't take enough time for the lower granularity to matter. Signed-off-by: NTejun Heo <tj@kernel.org> Link: http://lkml.kernel.org/g/55F8097A.7000206@de.ibm.com Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org>
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- 16 9月, 2015 1 次提交
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由 Tejun Heo 提交于
This reverts commit d59cfc09. d59cfc09 ("sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem") and b5ba75b5 ("cgroup: simplify threadgroup locking") changed how cgroup synchronizes against task fork and exits so that it uses global percpu_rwsem instead of per-process rwsem; unfortunately, the write [un]lock paths of percpu_rwsem always involve synchronize_rcu_expedited() which turned out to be too expensive. Improvements for percpu_rwsem are scheduled to be merged in the coming v4.4-rc1 merge window which alleviates this issue. For now, revert the two commits to restore per-process rwsem. They will be re-applied for the v4.4-rc1 merge window. Signed-off-by: NTejun Heo <tj@kernel.org> Link: http://lkml.kernel.org/g/55F8097A.7000206@de.ibm.comReported-by: NChristian Borntraeger <borntraeger@de.ibm.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: stable@vger.kernel.org # v4.2+
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- 19 8月, 2015 1 次提交
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由 Tejun Heo 提交于
This allows cgroup subsystems to use a different name on the unified hierarchy. cgroup_subsys->name is used on the unified hierarchy, ->legacy_name elsewhere. If ->legacy_name is not explicitly set, it's automatically set to ->name and the userland visible behavior remains unchanged. v2: Make parse_cgroupfs_options() only consider ->legacy_name as mount options are used only on legacy hierarchies. Suggested by Li Zefan. Signed-off-by: NTejun Heo <tj@kernel.org> Acked-by: NLi Zefan <lizefan@huawei.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: cgroups@vger.kernel.org
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- 12 8月, 2015 1 次提交
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由 Tejun Heo 提交于
It's pretty unusual to have an int as a private data field and it makes it impossible to carray a pointer value through it. Let's make it an unsigned long. AFAICS, this shouldn't break anything. Signed-off-by: NTejun Heo <tj@kernel.org> Acked-by: NLi Zefan <lizefan@huawei.com> Cc: Johannes Weiner <hannes@cmpxchg.org>
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- 15 7月, 2015 1 次提交
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由 Aleksa Sarai 提交于
Add a new cgroup subsystem callback can_fork that conditionally states whether or not the fork is accepted or rejected by a cgroup policy. In addition, add a cancel_fork callback so that if an error occurs later in the forking process, any state modified by can_fork can be reverted. Allow for a private opaque pointer to be passed from cgroup_can_fork to cgroup_post_fork, allowing for the fork state to be stored by each subsystem separately. Also add a tagging system for cgroup_subsys.h to allow for CGROUP_<TAG> enumerations to be be defined and used. In addition, explicitly add a CGROUP_CANFORK_COUNT macro to make arrays easier to define. This is in preparation for implementing the pids cgroup subsystem. Signed-off-by: NAleksa Sarai <cyphar@cyphar.com> Signed-off-by: NTejun Heo <tj@kernel.org>
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- 19 6月, 2015 1 次提交
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由 Tejun Heo 提交于
On traditional hierarchies, if a task has write access to "tasks" or "cgroup.procs" file of a cgroup and its euid agrees with the target, it can move the target to the cgroup; however, consider the following scenario. The owner of each cgroup is in the parentheses. R (root) - 0 (root) - 00 (user1) - 000 (user1) | \ 001 (user1) \ 1 (root) - 10 (user1) The subtrees of 00 and 10 are delegated to user1; however, while both subtrees may belong to the same user, it is clear that the two subtrees are to be isolated - they're under completely separate resource limits imposed by 0 and 1, respectively. Note that 0 and 1 aren't strictly necessary but added to ease illustrating the issue. If user1 is allowed to move processes between the two subtrees, the intention of the hierarchy - keeping a given group of processes under a subtree with certain resource restrictions while delegating management of the subtree - can be circumvented by user1. This happens because migration permission check doesn't consider the hierarchical nature of cgroups. To fix the issue, this patch adds an extra permission requirement when userland tries to migrate a process in the default hierarchy - the issuing task must have write access to the common ancestor of "cgroup.procs" file of the ancestor in addition to the destination's. Conceptually, the issuer must be able to move the target process from the source cgroup to the common ancestor of source and destination cgroups and then to the destination. As long as delegation is done in a proper top-down way, this guarantees that a delegatee can't smuggle processes across disjoint delegation domains. The next patch will add documentation on the delegation model on the default hierarchy. v2: Fixed missing !ret test. Spotted by Li Zefan. Signed-off-by: NTejun Heo <tj@kernel.org> Acked-by: NJohannes Weiner <hannes@cmpxchg.org> Cc: Li Zefan <lizefan@huawei.com>
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- 08 6月, 2015 1 次提交
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由 Aleksa Sarai 提交于
Add a new macro for_each_subsys_which that allows all enabled cgroup subsystems to be filtered by a bitmask, such that mask & (1 << ssid) determines if the subsystem is to be processed in the loop body (where ssid is the unique id of the subsystem). Also replace the need_forkexit_callback with two separate bitmasks for each callback to make (ss->{fork,exit}) checks unnecessary. tj: add a short comment for "if (!CGROUP_SUBSYS_COUNT)". Signed-off-by: NAleksa Sarai <cyphar@cyphar.com>
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- 29 5月, 2015 1 次提交
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由 Arnd Bergmann 提交于
Recent header file changes for cgroup caused lots of warnings about a missing struct seq_file form declaration for every inclusion of include/linux/cgroup-defs.h. As some files are built with -Werror, this leads to build failure like: from /git/arm-soc/drivers/gpu/drm/tilcdc/tilcdc_crtc.c:18: /git/arm-soc/include/linux/cgroup-defs.h:354:25: error: 'struct seq_file' declared inside parameter list [-Werror] cc1: all warnings being treated as errors make[6]: *** [drivers/gpu/drm/tilcdc/tilcdc_crtc.o] Error 1 This patch adds the declaration, which resolves both the warnings and the drm failure. tj: Moved it where other type declarations are. Signed-off-by: NArnd Bergmann <arnd@arndb.de> Fixes: b4a04ab7 ("cgroup: separate out include/linux/cgroup-defs.h") Signed-off-by: NTejun Heo <tj@kernel.org>
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- 27 5月, 2015 2 次提交
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由 Tejun Heo 提交于
The cgroup side of threadgroup locking uses signal_struct->group_rwsem to synchronize against threadgroup changes. This per-process rwsem adds small overhead to thread creation, exit and exec paths, forces cgroup code paths to do lock-verify-unlock-retry dance in a couple places and makes it impossible to atomically perform operations across multiple processes. This patch replaces signal_struct->group_rwsem with a global percpu_rwsem cgroup_threadgroup_rwsem which is cheaper on the reader side and contained in cgroups proper. This patch converts one-to-one. This does make writer side heavier and lower the granularity; however, cgroup process migration is a fairly cold path, we do want to optimize thread operations over it and cgroup migration operations don't take enough time for the lower granularity to matter. Signed-off-by: NTejun Heo <tj@kernel.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org>
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由 Tejun Heo 提交于
threadgroup_change_begin/end() are used to mark the beginning and end of threadgroup modifying operations to allow code paths which require a threadgroup to stay stable across blocking operations to synchronize against those sections using threadgroup_lock/unlock(). It's currently implemented as a general mechanism in sched.h using per-signal_struct rwsem; however, this never grew non-cgroup use cases and becomes noop if !CONFIG_CGROUPS. It turns out that cgroups is gonna be better served with a different sycnrhonization scheme and is a bit silly to keep cgroups specific details as a general mechanism. What's general here is identifying the places where threadgroups are modified. This patch restructures threadgroup locking so that threadgroup_change_begin/end() become a place where subsystems which need to sycnhronize against threadgroup changes can hook into. cgroup_threadgroup_change_begin/end() which operate on the per-signal_struct rwsem are created and threadgroup_lock/unlock() are moved to cgroup.c and made static. This is pure reorganization which doesn't cause any functional changes. Signed-off-by: NTejun Heo <tj@kernel.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org>
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- 19 5月, 2015 1 次提交
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由 Tejun Heo 提交于
From 2d728f74bfc071df06773e2fd7577dd5dab6425d Mon Sep 17 00:00:00 2001 From: Tejun Heo <tj@kernel.org> Date: Wed, 13 May 2015 15:37:01 -0400 This patch separates out cgroup-defs.h from cgroup.h which has grown a lot of dependencies. cgroup-defs.h currently only contains constant and type definitions and can be used to break circular include dependency. While moving, definitions are reordered so that cgroup-defs.h has consistent logical structure. This patch is pure reorganization. Signed-off-by: NTejun Heo <tj@kernel.org>
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