- 13 Feb, 2014 7 commits
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Tejun Heo authored
Currently there are two ways to walk tasks of a cgroup - css_task_iter_start/next/end() and css_scan_tasks(). The latter builds on the former but allows blocking while iterating. Unfortunately, the way css_scan_tasks() is implemented is rather nasty, it uses a priority heap of pointers to extract some number of tasks in task creation order and loops over them invoking the callback and repeats that until it reaches the end. It requires either preallocated heap or may fail under memory pressure, while unlikely to be problematic, the complexity is O(N^2), and in general just nasty. We're gonna convert all css_scan_users() to css_task_iter_start/next/end() and remove css_scan_users(). As css_scan_tasks() users may block, let's convert css_set_lock to a rwsem so that tasks can block during css_task_iter_*() is in progress. While this does increase the chance of possible deadlock scenarios, given the current usage, the probability is relatively low, and even if that happens, the right thing to do is updating the iteration in the similar way to css iterators so that it can handle blocking. Most conversions are trivial; however, task_cgroup_path() now expects to be called with css_set_rwsem locked instead of locking itself. This is because the function is called with RCU read lock held and rwsem locking should nest outside RCU read lock. Signed-off-by:
Tejun Heo <tj@kernel.org> Acked-by:
Li Zefan <lizefan@huawei.com>
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Tejun Heo authored
Reimplement cgroup_transfer_tasks() so that it repeatedly fetches the first task in the cgroup and then tranfers it. This achieves the same result without using css_scan_tasks() which is scheduled to be removed. Signed-off-by:
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Tejun Heo authored
cgroup_task_count() read-locks css_set_lock and walks all tasks to count them and then returns the result. The only thing all the users want is determining whether the cgroup is empty or not. This patch implements cgroup_has_tasks() which tests whether cgroup->cset_links is empty, replaces all cgroup_task_count() usages and unexports it. Note that the test isn't synchronized. This is the same as before. The test has always been racy. This will help planned css_set locking update. Signed-off-by:
Michal Hocko <mhocko@suse.cz> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Balbir Singh <bsingharora@gmail.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
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Tejun Heo authored
Move it above so that prototype isn't necessary. Let's also move the definition of use_task_css_set_links next to it. This is purely cosmetic. Signed-off-by:
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Tejun Heo authored
Tasks are not linked on their css_sets until cgroup task iteration is actually used. This is to avoid incurring overhead on the fork and exit paths for systems which have cgroup compiled in but don't use it. This lazy binding also affects the task migration path. It has to be careful so that it doesn't link tasks to css_sets when task_cg_lists linking is not enabled yet. Unfortunately, this conditional linking in the migration path interferes with planned migration updates. This patch moves the lazy binding a bit earlier, to the first cgroup mount. It's a clear indication that cgroup is being used on the system and task_cg_lists linking is highly likely to be enabled soon anyway through "tasks" and "cgroup.procs" files. This allows cgroup_task_migrate() to always link @tsk->cg_list. Note that it may still race with cgroup_post_fork() but who wins that race is inconsequential. While at it, make use_task_css_set_links a bool, add sanity checks in cgroup_enable_task_cg_lists() and css_task_iter_start(), and update the former so that it's guaranteed and assumes to run only once. Signed-off-by: -
Tejun Heo authored
Before kernfs conversion, due to the way super_block lookup works, cgroup roots were created and made visible before being fully initialized. This in turn required a special flag to mark that the root hasn't been fully initialized so that the destruction path can tell fully bound ones from half initialized. That flag is CGRP_ROOT_SUBSYS_BOUND and no longer necessary after the kernfs conversion as the lookup and creation of new root are atomic w.r.t. cgroup_mutex. This patch removes the flag and passes the requests subsystem mask to cgroup_setup_root() so that it can set the respective mask bits as subsystems are bound. Signed-off-by:
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Tejun Heo authored
Disallow more mount options if sane_behavior. Note that xattr used to generate warning. While at it, simplify option check in cgroup_mount() and update sane_behavior comment in cgroup.h. Signed-off-by:
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- 12 Feb, 2014 9 commits
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Stephen Rothwell authored
This was being included implicitly via cgroup.h's inclusion of xattr.h (which has now been removed). Signed-off-by:
Stephen Rothwell <sfr@canb.auug.org.au> Acked-by:
Sam Ravnborg <sam@ravnborg.org> Signed-off-by:
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Tejun Heo authored
Currently, cgroupfs_root and its ->top_cgroup are separated reference counted and the latter's is ignored. There's no reason to do this separately. This patch removes cgroupfs_root->refcnt and destroys cgroupfs_root when the top_cgroup is released. * cgroup_put() updated to ignore cgroup_is_dead() test for top cgroups. cgroup_free_fn() updated to handle root destruction when releasing a top cgroup. * As root destruction is now bounced through cgroup destruction, it is asynchronous. Update cgroup_mount() so that it waits for pending release which is currently implemented using msleep(). Converting this to proper wait_queue isn't hard but likely unnecessary. Signed-off-by:
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Tejun Heo authored
root->number_of_cgroups is currently an integer protected with cgroup_mutex. Except for sanity checks and proc reporting, the only place it's used is to check whether the root has any child during remount; however, this is a bit flawed as the counter is not decremented when the cgroup is unlinked but when it's released, meaning that there could be an extended period where all cgroups are removed but remount is still not allowed because some internal objects are lingering. While not perfect either, it'd be better to use emptiness test on root->top_cgroup.children. This patch updates cgroup_remount() to test top_cgroup's children instead, which makes number_of_cgroups only actual usage statistics printing in proc implemented in proc_cgroupstats_show(). Let's shorten its name and make it an atomic_t so that we don't have to worry about its synchronization. It's purely auxiliary at this point. Signed-off-by:
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Tejun Heo authored
cgroup->name handling became quite complicated over time involving dedicated struct cgroup_name for RCU protection. Now that cgroup is on kernfs, we can drop all of it and simply use kernfs_name/path() and friends. Replace cgroup->name and all related code with kernfs name/path constructs. * Reimplement cgroup_name() and cgroup_path() as thin wrappers on top of kernfs counterparts, which involves semantic changes. pr_cont_cgroup_name() and pr_cont_cgroup_path() added. * cgroup->name handling dropped from cgroup_rename(). * All users of cgroup_name/path() updated to the new semantics. Users which were formatting the string just to printk them are converted to use pr_cont_cgroup_name/path() instead, which simplifies things quite a bit. As cgroup_name() no longer requires RCU read lock around it, RCU lockings which were protecting only cgroup_name() are removed. v2: Comment above oom_info_lock updated as suggested by Michal. v3: dummy_top doesn't have a kn associated and pr_cont_cgroup_name/path() ended up calling the matching kernfs functions with NULL kn leading to oops. Test for NULL kn and print "/" if so. This issue was reported by Fengguang Wu. v4: Rebased on top of 0ab02ca8 ("cgroup: protect modifications to cgroup_idr with cgroup_mutex"). Signed-off-by:Peter Zijlstra <peterz@infradead.org> Acked-by:
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Tejun Heo authored
cgroup currently releases its kernfs_node when it gets removed. While not buggy, this makes cgroup->kn access rules complicated than necessary and leads to things like get/put protection around kernfs_remove() in cgroup_destroy_locked(). In addition, we want to use kernfs_name/path() and friends but also want to be able to determine a cgroup's name between removal and release. This patch makes cgroup hold onto its kernfs_node until freed so that cgroup->kn is always accessible. Signed-off-by:
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Tejun Heo authored
Dynamic cftype addition and removal using cgroup_add/rm_cftypes() respectively has been quite hairy due to vfs i_mutex. As i_mutex nests outside cgroup_mutex, cgroup_mutex has to be released and regrabbed on each iteration through the hierarchy complicating the process. Now that i_mutex is no longer in play, it can be simplified. * Just holding cgroup_tree_mutex is enough. No need to meddle with cgroup_mutex. * No reason to play the unlock - relock - check serial_nr dancing. Everything can be atomically while holding cgroup_tree_mutex. * cgroup_cfts_prepare() is replaced with direct locking of cgroup_tree_mutex. * cgroup_cfts_commit() no longer fiddles with locking. It just applies the cftypes change to the existing cgroups in the hierarchy. Renamed to cgroup_cfts_apply(). Signed-off-by:
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Tejun Heo authored
cftype_set was added primarily to allow registering the same cftype array more than once for different subsystems. Nobody uses or needs such thing and it's already broken because each cftype has ->ss pointer which is initialized during registration. Let's add list_head ->node to cftype and use the first cftype entry in the array to link them instead of allocating separate cftype_set. While at it, trigger WARN if cft seems previously initialized during registration. This simplifies cftype handling a bit. Signed-off-by:
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Tejun Heo authored
cftype handling is about to be revamped. Relocate cgroup_rm_cftypes() above cgroup_add_cftypes() in preparation. This is pure relocation. Signed-off-by:
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Tejun Heo authored
Mount option "xattr" is no longer necessary as it's enabled by default on kernfs. Warn if "xattr" is specified with "sane_behavior" so that the option can be removed in the future. Signed-off-by:
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- 11 Feb, 2014 15 commits
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Tejun Heo authored
cgroup filesystem code was derived from the original sysfs implementation which was heavily intertwined with vfs objects and locking with the goal of re-using the existing vfs infrastructure. That experiment turned out rather disastrous and sysfs switched, a long time ago, to distributed filesystem model where a separate representation is maintained which is queried by vfs. Unfortunately, cgroup stuck with the failed experiment all these years and accumulated even more problems over time. Locking and object lifetime management being entangled with vfs is probably the most egregious. vfs is never designed to be misused like this and cgroup ends up jumping through various convoluted dancing to make things work. Even then, operations across multiple cgroups can't be done safely as it'll deadlock with rename locking. Recently, kernfs is separated out from sysfs so that it can be used by users other than sysfs. This patch converts cgroup to use kernfs, which will bring the following benefits. * Separation from vfs internals. Locking and object lifetime management is contained in cgroup proper making things a lot simpler. This removes significant amount of locking convolutions, hairy object lifetime rules and the restriction on multi-cgroup operations. * Can drop a lot of code to implement filesystem interface as most are provided by kernfs. * Proper "severing" semantics, which allows controllers to not worry about lingering file accesses after offline. While the preceding patches did as much as possible to make the transition less painful, large part of the conversion has to be one discrete step making this patch rather large. The rest of the commit message lists notable changes in different areas. Overall ------- * vfs constructs replaced with kernfs ones. cgroup->dentry w/ ->kn, cgroupfs_root->sb w/ ->kf_root. * All dentry accessors are removed. Helpers to map from kernfs constructs are added. * All vfs plumbing around dentry, inode and bdi removed. * cgroup_mount() now directly looks for matching root and then proceeds to create a new one if not found. Synchronization and object lifetime ----------------------------------- * vfs inode locking removed. Among other things, this removes the need for the convolution in cgroup_cfts_commit(). Future patches will further simplify it. * vfs refcnting replaced with cgroup internal ones. cgroup->refcnt, cgroupfs_root->refcnt added. cgroup_put_root() now directly puts root->refcnt and when it reaches zero proceeds to destroy it thus merging cgroup_put_root() and the former cgroup_kill_sb(). Simliarly, cgroup_put() now directly schedules cgroup_free_rcu() when refcnt reaches zero. * Unlike before, kernfs objects don't hold onto cgroup objects. When cgroup destroys a kernfs node, all existing operations are drained and the association is broken immediately. The same for cgroupfs_roots and mounts. * All operations which come through kernfs guarantee that the associated cgroup is and stays valid for the duration of operation; however, there are two paths which need to find out the associated cgroup from dentry without going through kernfs - css_tryget_from_dir() and cgroupstats_build(). For these two, kernfs_node->priv is RCU managed so that they can dereference it under RCU read lock. File and directory handling --------------------------- * File and directory operations converted to kernfs_ops and kernfs_syscall_ops. * xattrs is implicitly supported by kernfs. No need to worry about it from cgroup. This means that "xattr" mount option is no longer necessary. A future patch will add a deprecated warning message when sane_behavior. * When cftype->max_write_len > PAGE_SIZE, it's necessary to make a private copy of one of the kernfs_ops to set its atomic_write_len. cftype->kf_ops is added and cgroup_init/exit_cftypes() are updated to handle it. * cftype->lockdep_key added so that kernfs lockdep annotation can be per cftype. * Inidividual file entries and open states are now managed by kernfs. No need to worry about them from cgroup. cfent, cgroup_open_file and their friends are removed. * kernfs_nodes are created deactivated and kernfs_activate() invocations added to places where creation of new nodes are committed. * cgroup_rmdir() uses kernfs_[un]break_active_protection() for self-removal. v2: - Li pointed out in an earlier patch that specifying "name=" during mount without subsystem specification should succeed if there's an existing hierarchy with a matching name although it should fail with -EINVAL if a new hierarchy should be created. Prior to the conversion, this used by handled by deferring failure from NULL return from cgroup_root_from_opts(), which was necessary because root was being created before checking for existing ones. Note that cgroup_root_from_opts() returned an ERR_PTR() value for error conditions which require immediate mount failure. As we now have separate search and creation steps, deferring failure from cgroup_root_from_opts() is no longer necessary. cgroup_root_from_opts() is updated to always return ERR_PTR() value on failure. - The logic to match existing roots is updated so that a mount attempt with a matching name but different subsys_mask are rejected. This was handled by a separate matching loop under the comment "Check for name clashes with existing mounts" but got lost during conversion. Merge the check into the main search loop. - Add __rcu __force casting in RCU_INIT_POINTER() in cgroup_destroy_locked() to avoid the sparse address space warning reported by kbuild test bot. Maybe we want an explicit interface to use kn->priv as RCU protected pointer? v3: Make CONFIG_CGROUPS select CONFIG_KERNFS. v4: Rebased on top of 0ab02ca8 ("cgroup: protect modifications to cgroup_idr with cgroup_mutex"). Signed-off-by: -
Tejun Heo authored
Relocate cgroup_init/exit_root_id(), cgroup_free_root(), cgroup_kill_sb() and cgroup_file_name() in preparation of kernfs conversion. These are pure relocations to make kernfs conversion easier to follow. Signed-off-by:
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Tejun Heo authored
* Un-inline seq_css(). After kernfs conversion, the function will need to dereference internal data structures. * Add cgroup_get/put_root() and replace direct super_block->s_active manipulatinos with them. These will be converted to kernfs_root refcnting. * Add cgroup_get/put() and replace dget/put() on cgrp->dentry with them. These will be converted to kernfs refcnting. * Update current_css_set_cg_links_read() to use cgroup_name() instead of reaching into the dentry name. The end result is the same. These changes don't make functional differences but will make transition to kernfs easier. v2: Rebased on top of 0ab02ca8 ("cgroup: protect modifications to cgroup_idr with cgroup_mutex"). Signed-off-by:
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Tejun Heo authored
mm/memory-failure.c::hwpoison_filter_task() has been reaching into cgroup to extract the associated ino to be used as a filtering criterion. This is an implementation detail which shouldn't be depended upon from outside cgroup proper and is about to change with the scheduled kernfs conversion. This patch introduces a proper interface to determine the associated ino, cgroup_ino(), and updates hwpoison_filter_task() to use it instead of reaching directly into cgroup. Signed-off-by:
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Tejun Heo authored
Factor out cft->ss initialization into cgroup_init_cftypes() from cgroup_add_cftypes() and add cft->ss clearing to cgroup_rm_cftypes() through cgroup_exit_cftypes(). This doesn't make any meaningful difference now but the two new functions will be expanded during kernfs transition. Signed-off-by:
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Tejun Heo authored
cftype->max_write_len is used to extend the maximum size of writes. It's interpreted in such a way that the actual maximum size is one less than the specified value. The default size is defined by CGROUP_LOCAL_BUFFER_SIZE. Its interpretation is quite confusing - its value is decremented by 1 and then compared for equality with max size, which means that the actual default size is CGROUP_LOCAL_BUFFER_SIZE - 2, which is 62 chars. There's no point in having a limit that low. Update its definition so that it means the actual string length sans termination and anything below PAGE_SIZE-1 is treated as PAGE_SIZE-1. .max_write_len for "release_agent" is updated to PATH_MAX-1 and cgroup_release_agent_write() is updated so that the redundant strlen() check is removed and it uses strlcpy() instead of strcpy(). .max_write_len initializations in blk-throttle.c and cfq-iosched.c are no longer necessary and removed. The one in cpuset is kept unchanged as it's an approximated value to begin with. This will also make transition to kernfs smoother. Signed-off-by:
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Tejun Heo authored
Currently, cgroup_subsys->base_cftypes registration is different from dynamic cftypes registartion. Instead of going through cgroup_add_cftypes(), cgroup_init_subsys() invokes cgroup_init_cftsets() which makes use of cgroup_subsys->base_cftset which doesn't involve dynamic allocation. While avoiding dynamic allocation is somewhat nice, having two separate paths for cftypes registration is nasty, especially as we're planning to add more operations during cftypes registration. This patch drops cgroup_init_cftsets() and cgroup_subsys->base_cftset and registers base_cftypes using cgroup_add_cftypes(). This is done as a separate step in cgroup_init() instead of a part of cgroup_init_subsys(). This is because cgroup_init_subsys() can be called very early during boot when kmalloc() isn't available yet. Signed-off-by:
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Tejun Heo authored
Straightforward updates to cgroup name handling in preparation of kernfs conversion. * cgroup_alloc_name() is updated to take const char * isntead of dentry * for name source. * cgroup name formatting is separated out into cgroup_file_name(). While at it, buffer length protection is added. Signed-off-by:
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Tejun Heo authored
Factor out new root initialization into cgroup_setup_root() from cgroup_mount(). This makes it easier to follow and will ease kernfs conversion. Signed-off-by:
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Tejun Heo authored
cgroup is scheduled to be converted to kernfs. After conversion, cgroup_mount() won't use the sget() machinery for finding out existing super_blocks but instead would do that directly. It'll search the existing cgroupfs_roots for a matching one and create a new one iff a match doesn't exist. To ease such conversion, this patch restructures locking and error handling of the function. cgroup_tree_mutex and cgroup_mutex are grabbed from the get-go and held until return. For now, due to the way vfs locks nest outside cgroup mutexes, the two cgroup mutexes are temporarily dropped across sget() and inode mutex locking, which looks quite ridiculous; however, these will be removed through kernfs conversion and structuring the code this way makes the conversion less painful. The error goto labels are consolidated to two. This looks unwieldy now but the next patch will factor out creation of new root into a separate function with accompanying error handling and it'll look a lot better. Signed-off-by:
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Tejun Heo authored
Now that cftypes and all tree modification operations are protected by cgroup_tree_mutex, we can drop cgroup_mutex while deleting files and directories. Drop cgroup_mutex over removals. This doesn't make any noticeable difference now but is to help kernfs conversion. In kernfs, removals are sync points which drain in-flight operations as those operations would grab cgroup_mutex, trying to delete under cgroup_mutex would deadlock. This can be resolved by just holding the outer cgroup_tree_mutex which nests outside both kernfs active reference and cgroup_mutex. Signed-off-by:
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Tejun Heo authored
Currently cgroup uses combination of inode->i_mutex'es and cgroup_mutex for synchronization. With the scheduled kernfs conversion, i_mutex'es will be removed. Unfortunately, just using cgroup_mutex isn't possible. All kernfs file and syscall operations, most of which require grabbing cgroup_mutex, will be called with kernfs active ref held and, if we try to perform kernfs removals under cgroup_mutex, it can deadlock as kernfs_remove() tries to drain the target node. Let's introduce a new outer mutex, cgroup_tree_mutex, which protects stuff used during hierarchy changing operations - cftypes and all the operations which may affect the cgroupfs. It also covers css association and iteration. This allows cgroup_css(), for_each_css() and other css iterators to be called under cgroup_tree_mutex. The new mutex will nest above both kernfs's active ref protection and cgroup_mutex. By protecting tree modifications with a separate outer mutex, we can get rid of the forementioned deadlock condition. Actual file additions and removals now require cgroup_tree_mutex instead of cgroup_mutex. Currently, cgroup_tree_mutex is never used without cgroup_mutex; however, we'll soon add hierarchy modification sections which are only protected by cgroup_tree_mutex. In the future, we might want to make the locking more granular by better splitting the coverages of the two mutexes. For now, this should do. v2: Rebased on top of 0ab02ca8 ("cgroup: protect modifications to cgroup_idr with cgroup_mutex"). Signed-off-by:
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Tejun Heo authored
css_from_dir() returns the matching css (cgroup_subsys_state) given a dentry and subsystem. The function doesn't pin the css before returning and requires the caller to be holding RCU read lock or cgroup_mutex and handling pinning on the caller side. Given that users of the function are likely to want to pin the returned css (both existing users do) and that getting and putting css's are very cheap, there's no reason for the interface to be tricky like this. Rename css_from_dir() to css_tryget_from_dir() and make it try to pin the found css and return it only if pinning succeeded. The callers are updated so that they no longer do RCU locking and pinning around the function and just use the returned css. This will also ease converting cgroup to kernfs. Signed-off-by:
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Tejun Heo authored
Pull for-3.14-fixes to receive 0ab02ca8 ("cgroup: protect modifications to cgroup_idr with cgroup_mutex") prior to kernfs conversion series to avoid non-trivial conflicts. Signed-off-by:
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Li Zefan authored
Setup cgroupfs like this: # mount -t cgroup -o cpuacct xxx /cgroup # mkdir /cgroup/sub1 # mkdir /cgroup/sub2 Then run these two commands: # for ((; ;)) { mkdir /cgroup/sub1/tmp && rmdir /mnt/sub1/tmp; } & # for ((; ;)) { mkdir /cgroup/sub2/tmp && rmdir /mnt/sub2/tmp; } & After seconds you may see this warning: ------------[ cut here ]------------ WARNING: CPU: 1 PID: 25243 at lib/idr.c:527 sub_remove+0x87/0x1b0() idr_remove called for id=6 which is not allocated. ... Call Trace: [<ffffffff8156063c>] dump_stack+0x7a/0x96 [<ffffffff810591ac>] warn_slowpath_common+0x8c/0xc0 [<ffffffff81059296>] warn_slowpath_fmt+0x46/0x50 [<ffffffff81300aa7>] sub_remove+0x87/0x1b0 [<ffffffff810f3f02>] ? css_killed_work_fn+0x32/0x1b0 [<ffffffff81300bf5>] idr_remove+0x25/0xd0 [<ffffffff810f2bab>] cgroup_destroy_css_killed+0x5b/0xc0 [<ffffffff810f4000>] css_killed_work_fn+0x130/0x1b0 [<ffffffff8107cdbc>] process_one_work+0x26c/0x550 [<ffffffff8107eefe>] worker_thread+0x12e/0x3b0 [<ffffffff81085f96>] kthread+0xe6/0xf0 [<ffffffff81570bac>] ret_from_fork+0x7c/0xb0 ---[ end trace 2d1577ec10cf80d0 ]--- It's because allocating/removing cgroup ID is not properly synchronized. The bug was introduced when we converted cgroup_ida to cgroup_idr. While synchronization is already done inside ida_simple_{get,remove}(), users are responsible for concurrent calls to idr_{alloc,remove}(). tj: Refreshed on top of b58c8998 ("cgroup: fix error return from cgroup_create()"). Fixes: 4e96ee8e ("cgroup: convert cgroup_ida to cgroup_idr") Cc: <stable@vger.kernel.org> #3.12+ Reported-by:
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- 08 Feb, 2014 9 commits
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Tejun Heo authored
Pending kernfs conversion depends on kernfs improvements in driver-core-next. Pull it into for-3.15. Signed-off-by: -
Tejun Heo authored
Pending kernfs conversion depends on fixes in for-3.14-fixes. Pull it into for-3.15. Signed-off-by: -
Tejun Heo authored
cgroup_root_mutex was added to avoid deadlock involving namespace_sem via cgroup_show_options(). It added a lot of overhead for the small purpose of it and, because it's nested under cgroup_mutex, it has very limited usefulness. The previous patch made cgroup_show_options() not use cgroup_root_mutex, so nobody needs it anymore. Remove it. Signed-off-by:
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Tejun Heo authored
cgroup_show_options() grabs cgroup_root_mutex to protect the options changing while printing; however, holding root_mutex or not doesn't really make much difference for the function. subsys_mask can be atomically tested and most of the options aren't allowed to change anyway once mounted. The only field which needs synchronization is ->release_agent_path. This patch introduces a dedicated spinlock to synchronize accesses to the field and drops cgroup_root_mutex locking from cgroup_show_options(). The next patch will remove cgroup_root_mutex. Signed-off-by:
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Tejun Heo authored
It's no longer referenced outside cgroup core, so renaming is easy. Let's rename it for consistency & brevity. This patch is pure rename. Signed-off-by:
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Tejun Heo authored
cgroup_subsys is a bit messier than it needs to be. * The name of a subsys can be different from its internal identifier defined in cgroup_subsys.h. Most subsystems use the matching name but three - cpu, memory and perf_event - use different ones. * cgroup_subsys_id enums are postfixed with _subsys_id and each cgroup_subsys is postfixed with _subsys. cgroup.h is widely included throughout various subsystems, it doesn't and shouldn't have claim on such generic names which don't have any qualifier indicating that they belong to cgroup. * cgroup_subsys->subsys_id should always equal the matching cgroup_subsys_id enum; however, we require each controller to initialize it and then BUG if they don't match, which is a bit silly. This patch cleans up cgroup_subsys names and initialization by doing the followings. * cgroup_subsys_id enums are now postfixed with _cgrp_id, and each cgroup_subsys with _cgrp_subsys. * With the above, renaming subsys identifiers to match the userland visible names doesn't cause any naming conflicts. All non-matching identifiers are renamed to match the official names. cpu_cgroup -> cpu mem_cgroup -> memory perf -> perf_event * controllers no longer need to initialize ->subsys_id and ->name. They're generated in cgroup core and set automatically during boot. * Redundant cgroup_subsys declarations removed. * While updating BUG_ON()s in cgroup_init_early(), convert them to WARN()s. BUGging that early during boot is stupid - the kernel can't print anything, even through serial console and the trap handler doesn't even link stack frame properly for back-tracing. This patch doesn't introduce any behavior changes. v2: Rebased on top of fe1217c4 ("net: net_cls: move cgroupfs classid handling into core"). Signed-off-by:
Neil Horman <nhorman@tuxdriver.com> Acked-by:
"David S. Miller" <davem@davemloft.net> Acked-by:
"Rafael J. Wysocki" <rjw@rjwysocki.net> Acked-by:
Aristeu Rozanski <aris@redhat.com> Acked-by:
Ingo Molnar <mingo@redhat.com> Acked-by:
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Tejun Heo authored
With module supported dropped from net_prio, no controller is using cgroup module support. None of actual resource controllers can be built as a module and we aren't gonna add new controllers which don't control resources. This patch drops module support from cgroup. * cgroup_[un]load_subsys() and cgroup_subsys->module removed. * As there's no point in distinguishing IS_BUILTIN() and IS_MODULE(), cgroup_subsys.h now uses IS_ENABLED() directly. * enum cgroup_subsys_id now exactly matches the list of enabled controllers as ordered in cgroup_subsys.h. * cgroup_subsys[] is now a contiguously occupied array. Size specification is no longer necessary and dropped. * for_each_builtin_subsys() is removed and for_each_subsys() is updated to not require any locking. * module ref handling is removed from rebind_subsystems(). * Module related comments dropped. v2: Rebased on top of fe1217c4 ("net: net_cls: move cgroupfs classid handling into core"). v3: Added {} around the if (need_forkexit_callback) block in cgroup_post_fork() for readability as suggested by Li. Signed-off-by:
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Tejun Heo authored
net_prio is the only cgroup which is allowed to be built as a module. The savings from allowing one controller to be built as a module are tiny especially given that cgroup module support itself adds quite a bit of complexity. Given that none of other controllers has much chance of being made a module and that we're unlikely to add new modular controllers, the added complexity is simply not justifiable. As a first step to drop cgroup module support, this patch changes the config option to bool from tristate and drops module related code from it. Also, while an earlier commit fe1217c4 ("net: net_cls: move cgroupfs classid handling into core") dropped module support from net_cls cgroup, it retained a call to cgroup_load_subsys(), which is noop for built-in controllers. Drop it along with init_netclassid_cgroup(). v2: Removed modular version of task_netprioidx() in include/net/netprio_cgroup.h as suggested by Li Zefan. v3: Rebased on top of fe1217c4 ("net: net_cls: move cgroupfs classid handling into core"). net_cls cgroup part is mostly dropped except for removal of init_netclassid_cgroup(). Signed-off-by:
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Tejun Heo authored
cgroup_cfts_commit() walks the cgroup hierarchy that the target subsystem is attached to and tries to apply the file changes. Due to the convolution with inode locking, it can't keep cgroup_mutex locked while iterating. It currently holds only RCU read lock around the actual iteration and then pins the found cgroup using dget(). Unfortunately, this is incorrect. Although the iteration does check cgroup_is_dead() before invoking dget(), there's nothing which prevents the dentry from going away inbetween. Note that this is different from the usual css iterations where css_tryget() is used to pin the css - css_tryget() tests whether the css can be pinned and fails if not. The problem can be solved by simply holding cgroup_mutex instead of RCU read lock around the iteration, which actually reduces LOC. Signed-off-by:
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