linux/kernel/cpuset.c, branch v3.16

cpuset: break kernfs active protection in cpuset_write_resmask()

2014-07-01T20:42:28Z

Writing to either "cpuset.cpus" or "cpuset.mems" file flushes cpuset_hotplug_work so that cpu or memory hotunplug doesn't end up migrating tasks off a cpuset after new resources are added to it. As cpuset_hotplug_work calls into cgroup core via cgroup_transfer_tasks(), this flushing adds the dependency to cgroup core locking from cpuset_write_resmak(). This used to be okay because cgroup interface files were protected by a different mutex; however, 8353da1f91f1 ("cgroup: remove cgroup_tree_mutex") simplified the cgroup core locking and this dependency became a deadlock hazard - cgroup file removal performed under cgroup core lock tries to drain on-going file operation which is trying to flush cpuset_hotplug_work blocked on the same cgroup core lock. The locking simplification was done because kernfs added an a lot easier way to deal with circular dependencies involving kernfs active protection. Let's use the same strategy in cpuset and break active protection in cpuset_write_resmask(). While it isn't the prettiest, this is a very rare, likely unique, situation which also goes away on the unified hierarchy. The commands to trigger the deadlock warning without the patch and the lockdep output follow. localhost:/ # mount -t cgroup -o cpuset xxx /cpuset localhost:/ # mkdir /cpuset/tmp localhost:/ # echo 1 > /cpuset/tmp/cpuset.cpus localhost:/ # echo 0 > cpuset/tmp/cpuset.mems localhost:/ # echo $$ > /cpuset/tmp/tasks localhost:/ # echo 0 > /sys/devices/system/cpu/cpu1/online ====================================================== [ INFO: possible circular locking dependency detected ] 3.16.0-rc1-0.1-default+ #7 Not tainted ------------------------------------------------------- kworker/1:0/32649 is trying to acquire lock: (cgroup_mutex){+.+.+.}, at: [] cgroup_transfer_tasks+0x37/0x150 but task is already holding lock: (cpuset_hotplug_work){+.+...}, at: [] process_one_work+0x192/0x520 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (cpuset_hotplug_work){+.+...}: ... -> #1 (s_active#175){++++.+}: ... -> #0 (cgroup_mutex){+.+.+.}: ... other info that might help us debug this: Chain exists of: cgroup_mutex --> s_active#175 --> cpuset_hotplug_work Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(cpuset_hotplug_work); lock(s_active#175); lock(cpuset_hotplug_work); lock(cgroup_mutex); *** DEADLOCK *** 2 locks held by kworker/1:0/32649: #0: ("events"){.+.+.+}, at: [] process_one_work+0x192/0x520 #1: (cpuset_hotplug_work){+.+...}, at: [] process_one_work+0x192/0x520 stack backtrace: CPU: 1 PID: 32649 Comm: kworker/1:0 Not tainted 3.16.0-rc1-0.1-default+ #7 ... Call Trace: [] dump_stack+0x72/0x8a [] print_circular_bug+0x10f/0x120 [] check_prev_add+0x43e/0x4b0 [] validate_chain+0x656/0x7c0 [] __lock_acquire+0x382/0x660 [] lock_acquire+0xf9/0x170 [] mutex_lock_nested+0x6f/0x380 [] cgroup_transfer_tasks+0x37/0x150 [] hotplug_update_tasks_insane+0x110/0x1d0 [] cpuset_hotplug_update_tasks+0x13d/0x180 [] cpuset_hotplug_workfn+0x18c/0x630 [] process_one_work+0x254/0x520 [] worker_thread+0x13d/0x3d0 [] kthread+0xf8/0x100 [] ret_from_fork+0x7c/0xb0 Signed-off-by: Tejun Heo Reported-by: Li Zefan Tested-by: Li Zefan

cpuset,mempolicy: fix sleeping function called from invalid context

2014-06-25T13:42:11Z

When runing with the kernel(3.15-rc7+), the follow bug occurs: [ 9969.258987] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:586 [ 9969.359906] in_atomic(): 1, irqs_disabled(): 0, pid: 160655, name: python [ 9969.441175] INFO: lockdep is turned off. [ 9969.488184] CPU: 26 PID: 160655 Comm: python Tainted: G A 3.15.0-rc7+ #85 [ 9969.581032] Hardware name: FUJITSU-SV PRIMEQUEST 1800E/SB, BIOS PRIMEQUEST 1000 Series BIOS Version 1.39 11/16/2012 [ 9969.706052] ffffffff81a20e60 ffff8803e941fbd0 ffffffff8162f523 ffff8803e941fd18 [ 9969.795323] ffff8803e941fbe0 ffffffff8109995a ffff8803e941fc58 ffffffff81633e6c [ 9969.884710] ffffffff811ba5dc ffff880405c6b480 ffff88041fdd90a0 0000000000002000 [ 9969.974071] Call Trace: [ 9970.003403] [] dump_stack+0x4d/0x66 [ 9970.065074] [] __might_sleep+0xfa/0x130 [ 9970.130743] [] mutex_lock_nested+0x3c/0x4f0 [ 9970.200638] [] ? kmem_cache_alloc+0x1bc/0x210 [ 9970.272610] [] cpuset_mems_allowed+0x27/0x140 [ 9970.344584] [] ? __mpol_dup+0x63/0x150 [ 9970.409282] [] __mpol_dup+0xe5/0x150 [ 9970.471897] [] ? __mpol_dup+0x63/0x150 [ 9970.536585] [] ? copy_process.part.23+0x606/0x1d40 [ 9970.613763] [] ? trace_hardirqs_on+0xd/0x10 [ 9970.683660] [] ? monotonic_to_bootbased+0x2f/0x50 [ 9970.759795] [] copy_process.part.23+0x670/0x1d40 [ 9970.834885] [] do_fork+0xd8/0x380 [ 9970.894375] [] ? __audit_syscall_entry+0x9c/0xf0 [ 9970.969470] [] SyS_clone+0x16/0x20 [ 9971.030011] [] stub_clone+0x69/0x90 [ 9971.091573] [] ? system_call_fastpath+0x16/0x1b The cause is that cpuset_mems_allowed() try to take mutex_lock(&callback_mutex) under the rcu_read_lock(which was hold in __mpol_dup()). And in cpuset_mems_allowed(), the access to cpuset is under rcu_read_lock, so in __mpol_dup, we can reduce the rcu_read_lock protection region to protect the access to cpuset only in current_cpuset_is_being_rebound(). So that we can avoid this bug. This patch is a temporary solution that just addresses the bug mentioned above, can not fix the long-standing issue about cpuset.mems rebinding on fork(): "When the forker's task_struct is duplicated (which includes ->mems_allowed) and it races with an update to cpuset_being_rebound in update_tasks_nodemask() then the task's mems_allowed doesn't get updated. And the child task's mems_allowed can be wrong if the cpuset's nodemask changes before the child has been added to the cgroup's tasklist." Signed-off-by: Gu Zheng Acked-by: Li Zefan Signed-off-by: Tejun Heo Cc: stable

Merge branch 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

2014-06-09T22:03:33Z

Pull cgroup updates from Tejun Heo: "A lot of activities on cgroup side. Heavy restructuring including locking simplification took place to improve the code base and enable implementation of the unified hierarchy, which currently exists behind a __DEVEL__ mount option. The core support is mostly complete but individual controllers need further work. To explain the design and rationales of the the unified hierarchy Documentation/cgroups/unified-hierarchy.txt is added. Another notable change is css (cgroup_subsys_state - what each controller uses to identify and interact with a cgroup) iteration update. This is part of continuing updates on css object lifetime and visibility. cgroup started with reference count draining on removal way back and is now reaching a point where csses behave and are iterated like normal refcnted objects albeit with some complexities to allow distinguishing the state where they're being deleted. The css iteration update isn't taken advantage of yet but is planned to be used to simplify memcg significantly" * 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (77 commits) cgroup: disallow disabled controllers on the default hierarchy cgroup: don't destroy the default root cgroup: disallow debug controller on the default hierarchy cgroup: clean up MAINTAINERS entries cgroup: implement css_tryget() device_cgroup: use css_has_online_children() instead of has_children() cgroup: convert cgroup_has_live_children() into css_has_online_children() cgroup: use CSS_ONLINE instead of CGRP_DEAD cgroup: iterate cgroup_subsys_states directly cgroup: introduce CSS_RELEASED and reduce css iteration fallback window cgroup: move cgroup->serial_nr into cgroup_subsys_state cgroup: link all cgroup_subsys_states in their sibling lists cgroup: move cgroup->sibling and ->children into cgroup_subsys_state cgroup: remove cgroup->parent device_cgroup: remove direct access to cgroup->children memcg: update memcg_has_children() to use css_next_child() memcg: remove tasks/children test from mem_cgroup_force_empty() cgroup: remove css_parent() cgroup: skip refcnting on normal root csses and cgrp_dfl_root self css cgroup: use cgroup->self.refcnt for cgroup refcnting ...

mm: page_alloc: use jump labels to avoid checking number_of_cpusets

2014-06-04T23:54:08Z

If cpusets are not in use then we still check a global variable on every page allocation. Use jump labels to avoid the overhead. Signed-off-by: Mel Gorman Reviewed-by: Rik van Riel Cc: Johannes Weiner Cc: Vlastimil Babka Cc: Jan Kara Cc: Michal Hocko Cc: Hugh Dickins Cc: Dave Hansen Cc: Theodore Ts'o Cc: "Paul E. McKenney" Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Stephen Rothwell Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

cgroup: remove css_parent()

2014-05-16T17:22:48Z

cgroup in general is moving towards using cgroup_subsys_state as the fundamental structural component and css_parent() was introduced to convert from using cgroup->parent to css->parent. It was quite some time ago and we're moving forward with making css more prominent. This patch drops the trivial wrapper css_parent() and let the users dereference css->parent. While at it, explicitly mark fields of css which are public and immutable. v2: New usage from device_cgroup.c converted. Signed-off-by: Tejun Heo Acked-by: Michal Hocko Acked-by: Neil Horman Acked-by: "David S. Miller" Acked-by: Li Zefan Cc: Vivek Goyal Cc: Jens Axboe Cc: Peter Zijlstra Cc: Johannes Weiner

cgroup: replace cftype->write_string() with cftype->write()

2014-05-13T16:16:21Z

Convert all cftype->write_string() users to the new cftype->write() which maps directly to kernfs write operation and has full access to kernfs and cgroup contexts. The conversions are mostly mechanical. * @css and @cft are accessed using of_css() and of_cft() accessors respectively instead of being specified as arguments. * Should return @nbytes on success instead of 0. * @buf is not trimmed automatically. Trim if necessary. Note that blkcg and netprio don't need this as the parsers already handle whitespaces. cftype->write_string() has no user left after the conversions and removed. While at it, remove unnecessary local variable @p in cgroup_subtree_control_write() and stale comment about CGROUP_LOCAL_BUFFER_SIZE in cgroup_freezer.c. This patch doesn't introduce any visible behavior changes. v2: netprio was missing from conversion. Converted. Signed-off-by: Tejun Heo Acked-by: Aristeu Rozanski Acked-by: Vivek Goyal Acked-by: Li Zefan Cc: Jens Axboe Cc: Johannes Weiner Cc: Michal Hocko Cc: Neil Horman Cc: "David S. Miller"

cgroup: rename css_tryget() to css_tryget_online()

2014-05-13T16:11:01Z

Unlike the more usual refcnting, what css_tryget() provides is the distinction between online and offline csses instead of protection against upping a refcnt which already reached zero. cgroup is planning to provide actual tryget which fails if the refcnt already reached zero. Let's rename the existing trygets so that they clearly indicate that they're onliness. I thought about keeping the existing names as-are and introducing new names for the planned actual tryget; however, given that each controller participates in the synchronization of the online state, it seems worthwhile to make it explicit that these functions are about on/offline state. Rename css_tryget() to css_tryget_online() and css_tryget_from_dir() to css_tryget_online_from_dir(). This is pure rename. v2: cgroup_freezer grew new usages of css_tryget(). Update accordingly. Signed-off-by: Tejun Heo Acked-by: Johannes Weiner Acked-by: Michal Hocko Acked-by: Li Zefan Cc: Vivek Goyal Cc: Jens Axboe Cc: Peter Zijlstra Cc: Paul Mackerras Cc: Ingo Molnar Cc: Arnaldo Carvalho de Melo

kernel/cpuset.c: convert printk to pr_foo()

2014-05-06T11:31:14Z

Cc: Andrew Morton Signed-off-by: Fabian Frederick Acked-by: Li Zefan Signed-off-by: Tejun Heo

kernel/cpuset.c: kernel-doc fixes

2014-05-06T11:31:14Z

This patch also converts seq_printf to seq_puts Cc: Andrew Morton Signed-off-by: Fabian Frederick Acked-by: Li Zefan Signed-off-by: Tejun Heo

Merge branch 'akpm' (incoming from Andrew)

2014-04-03T23:22:16Z

Merge first patch-bomb from Andrew Morton: - Various misc bits - kmemleak fixes - small befs, codafs, cifs, efs, freexxfs, hfsplus, minixfs, reiserfs things - fanotify - I appear to have become SuperH maintainer - ocfs2 updates - direct-io tweaks - a bit of the MM queue - printk updates - MAINTAINERS maintenance - some backlight things - lib/ updates - checkpatch updates - the rtc queue - nilfs2 updates - Small Documentation/ updates * emailed patches from Andrew Morton : (237 commits) Documentation/SubmittingPatches: remove references to patch-scripts Documentation/SubmittingPatches: update some dead URLs Documentation/filesystems/ntfs.txt: remove changelog reference Documentation/kmemleak.txt: updates fs/reiserfs/super.c: add __init to init_inodecache fs/reiserfs: move prototype declaration to header file fs/hfsplus/attributes.c: add __init to hfsplus_create_attr_tree_cache() fs/hfsplus/extents.c: fix concurrent acess of alloc_blocks fs/hfsplus/extents.c: remove unused variable in hfsplus_get_block nilfs2: update project's web site in nilfs2.txt nilfs2: update MAINTAINERS file entries fix nilfs2: verify metadata sizes read from disk nilfs2: add FITRIM ioctl support for nilfs2 nilfs2: add nilfs_sufile_trim_fs to trim clean segs nilfs2: implementation of NILFS_IOCTL_SET_SUINFO ioctl nilfs2: add nilfs_sufile_set_suinfo to update segment usage nilfs2: add struct nilfs_suinfo_update and flags nilfs2: update MAINTAINERS file entries fs/coda/inode.c: add __init to init_inodecache() BEFS: logging cleanup ...

linux/kernel/cpuset.c, branch v3.16

cpuset: break kernfs active protection in cpuset_write_resmask()

cpuset,mempolicy: fix sleeping function called from invalid context

Merge branch 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

mm: page_alloc: use jump labels to avoid checking number_of_cpusets

cgroup: remove css_parent()

cgroup: replace cftype->write_string() with cftype->write()

cgroup: rename css_tryget*() to css_tryget_online*()

kernel/cpuset.c: convert printk to pr_foo()

kernel/cpuset.c: kernel-doc fixes

Merge branch 'akpm' (incoming from Andrew)

cgroup: rename css_tryget() to css_tryget_online()