Tejun Heo 18fa84a2db cgroup: Use css_tryget() instead of css_tryget_online() in task_get_css() ... A PF_EXITING task can stay associated with an offline css. If such task calls task_get_css(), it can get stuck indefinitely. This can be triggered by BSD process accounting which writes to a file with PF_EXITING set when racing against memcg disable as in the backtrace at the end. After this change, task_get_css() may return a css which was already offline when the function was called. None of the existing users are affected by this change. INFO: rcu_sched self-detected stall on CPU INFO: rcu_sched detected stalls on CPUs/tasks: ... NMI backtrace for cpu 0 ... Call Trace: <IRQ> dump_stack+0x46/0x68 nmi_cpu_backtrace.cold.2+0x13/0x57 nmi_trigger_cpumask_backtrace+0xba/0xca rcu_dump_cpu_stacks+0x9e/0xce rcu_check_callbacks.cold.74+0x2af/0x433 update_process_times+0x28/0x60 tick_sched_timer+0x34/0x70 __hrtimer_run_queues+0xee/0x250 hrtimer_interrupt+0xf4/0x210 smp_apic_timer_interrupt+0x56/0x110 apic_timer_interrupt+0xf/0x20 </IRQ> RIP: 0010:balance_dirty_pages_ratelimited+0x28f/0x3d0 ... btrfs_file_write_iter+0x31b/0x563 __vfs_write+0xfa/0x140 __kernel_write+0x4f/0x100 do_acct_process+0x495/0x580 acct_process+0xb9/0xdb do_exit+0x748/0xa00 do_group_exit+0x3a/0xa0 get_signal+0x254/0x560 do_signal+0x23/0x5c0 exit_to_usermode_loop+0x5d/0xa0 prepare_exit_to_usermode+0x53/0x80 retint_user+0x8/0x8 Signed-off-by: Tejun Heo <tj@kernel.org> Cc: stable@vger.kernel.org # v4.2+ Fixes: ec438699a9 ("cgroup, block: implement task_get_css() and use it in bio_associate_current()")		2019-05-29 13:46:25 -07:00
..
acpi	More ACPI updates for 5.2-rc1	2019-05-15 08:58:49 -07:00
asm-generic	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 47	2019-05-24 17:27:13 +02:00
clocksource
crypto	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36	2019-05-24 17:27:11 +02:00
drm	drm pull request for 5.2	2019-05-08 21:35:19 -07:00
dt-bindings	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 61	2019-05-24 17:36:45 +02:00
keys	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36	2019-05-24 17:27:11 +02:00
kvm
linux	cgroup: Use css_tryget() instead of css_tryget_online() in task_get_css()	2019-05-29 13:46:25 -07:00
math-emu
media	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 61	2019-05-24 17:36:45 +02:00
memory
misc	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 61	2019-05-24 17:36:45 +02:00
net	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 104	2019-05-24 17:39:00 +02:00
pcmcia
ras
rdma	RDMA: Add EFA related definitions	2019-05-06 13:47:50 -03:00
scsi	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 59	2019-05-24 17:36:44 +02:00
soc	Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2019-05-19 11:11:20 -07:00
sound	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 61	2019-05-24 17:36:45 +02:00
target	scsi: target/iscsi: Handle too large immediate data buffers correctly	2019-04-12 20:20:06 -04:00
trace	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36	2019-05-24 17:27:11 +02:00
uapi	SPDX update for 5.2-rc2, round 2	2019-05-24 14:31:58 -07:00
video	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 27	2019-05-24 17:27:10 +02:00
xen	block: pass page to xen_biovec_phys_mergeable	2019-04-01 12:11:13 -06:00