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Josef Bacik 56001dda03 btrfs: avoid RCU stalls while running delayed iputs commit `71795ee590` upstream. Generally a delayed iput is added when we might do the final iput, so usually we'll end up sleeping while processing the delayed iputs naturally. However there's no guarantee of this, especially for small files. In production we noticed 5 instances of RCU stalls while testing a kernel release overnight across 1000 machines, so this is relatively common: host count: 5 rcu: INFO: rcu_sched self-detected stall on CPU rcu: ....: (20998 ticks this GP) idle=59e/1/0x4000000000000002 softirq=12333372/12333372 fqs=3208 (t=21031 jiffies g=27810193 q=41075) NMI backtrace for cpu 1 CPU: 1 PID: 1713 Comm: btrfs-cleaner Kdump: loaded Not tainted 5.6.13-0_fbk12_rc1_5520_gec92bffc1ec9 #1 Call Trace: <IRQ> dump_stack+0x50/0x70 nmi_cpu_backtrace.cold.6+0x30/0x65 ? lapic_can_unplug_cpu.cold.30+0x40/0x40 nmi_trigger_cpumask_backtrace+0xba/0xca rcu_dump_cpu_stacks+0x99/0xc7 rcu_sched_clock_irq.cold.90+0x1b2/0x3a3 ? trigger_load_balance+0x5c/0x200 ? tick_sched_do_timer+0x60/0x60 ? tick_sched_do_timer+0x60/0x60 update_process_times+0x24/0x50 tick_sched_timer+0x37/0x70 __hrtimer_run_queues+0xfe/0x270 hrtimer_interrupt+0xf4/0x210 smp_apic_timer_interrupt+0x5e/0x120 apic_timer_interrupt+0xf/0x20 </IRQ> RIP: 0010:queued_spin_lock_slowpath+0x17d/0x1b0 RSP: 0018:ffffc9000da5fe48 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13 RAX: 0000000000000000 RBX: ffff889fa81d0cd8 RCX: 0000000000000029 RDX: ffff889fff86c0c0 RSI: 0000000000080000 RDI: ffff88bfc2da7200 RBP: ffff888f2dcdd768 R08: 0000000001040000 R09: 0000000000000000 R10: 0000000000000001 R11: ffffffff82a55560 R12: ffff88bfc2da7200 R13: 0000000000000000 R14: ffff88bff6c2a360 R15: ffffffff814bd870 ? kzalloc.constprop.57+0x30/0x30 list_lru_add+0x5a/0x100 inode_lru_list_add+0x20/0x40 iput+0x1c1/0x1f0 run_delayed_iput_locked+0x46/0x90 btrfs_run_delayed_iputs+0x3f/0x60 cleaner_kthread+0xf2/0x120 kthread+0x10b/0x130 Fix this by adding a cond_resched_lock() to the loop processing delayed iputs so we can avoid these sort of stalls. CC: stable@vger.kernel.org # 4.9+ Reviewed-by: Rik van Riel <riel@surriel.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2021-05-26 12:06:50 +02:00
arch	powerpc: Fix early setup to make early_ioremap() work	2021-05-26 12:06:50 +02:00
block	blk-mq: Swap two calls in blk_mq_exit_queue()	2021-05-19 10:13:14 +02:00
certs	certs: Fix blacklist flag type confusion	2021-03-04 11:37:59 +01:00
crypto	async_xor: increase src_offs when dropping destination page	2021-05-14 09:49:59 +02:00
Documentation	tweewide: Fix most Shebang lines	2021-05-22 11:40:55 +02:00
drivers	nvmet: seset ns->file when open fails	2021-05-26 12:06:50 +02:00
fs	btrfs: avoid RCU stalls while running delayed iputs	2021-05-26 12:06:50 +02:00
include	virtio_net: Do not pull payload in skb->head	2021-05-22 11:40:52 +02:00
init	seccomp: Fix CONFIG tests for Seccomp_filters	2021-05-14 09:50:24 +02:00
ipc	ipc: adjust proc_ipc_sem_dointvec definition to match prototype	2020-09-05 12:14:29 -07:00
kernel	locking/mutex: clear MUTEX_FLAGS if wait_list is empty due to signal	2021-05-26 12:06:50 +02:00
lib	lib: stackdepot: turn depot_lock spinlock to raw_spinlock	2021-05-22 11:40:55 +02:00
LICENSES	LICENSES/deprecated: add Zlib license text	2020-09-16 14:33:49 +02:00
mm	mm/hugetlb: fix F_SEAL_FUTURE_WRITE	2021-05-19 10:13:11 +02:00
net	ipv6: remove extra dev_hold() for fallback tunnels	2021-05-22 11:40:55 +02:00
samples	samples/bpf: Fix broken tracex1 due to kprobe argument change	2021-05-19 10:12:57 +02:00
scripts	scripts: switch explicitly to Python 3	2021-05-22 11:40:55 +02:00
security	KEYS: trusted: Fix memory leak on object td	2021-05-19 10:12:50 +02:00
sound	ALSA: hda: generic: change the DAC ctl name for LO+SPK or LO+HP	2021-05-22 11:40:54 +02:00
tools	tools/testing/selftests/exec: fix link error	2021-05-26 12:06:49 +02:00
usr	Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2020-08-07 13:29:39 -07:00
virt	kvm: exit halt polling on need_resched() as well	2021-05-19 10:13:12 +02:00
.clang-format	RDMA 5.10 pull request	2020-10-17 11:18:18 -07:00
.cocciconfig
.get_maintainer.ignore	Opt out of scripts/get_maintainer.pl	2019-05-16 10:53:40 -07:00
.gitattributes	.gitattributes: use 'dts' diff driver for dts files	2019-12-04 19:44:11 -08:00
.gitignore	kbuild: generate Module.symvers only when vmlinux exists	2021-05-19 10:12:59 +02:00
.mailmap	mailmap: add two more addresses of Uwe Kleine-König	2020-12-06 10:19:07 -08:00
COPYING	COPYING: state that all contributions really are covered by this file	2020-02-10 13:32:20 -08:00
CREDITS	MAINTAINERS: Move Jason Cooper to CREDITS	2020-11-30 10:20:34 +01:00
Kbuild	kbuild: rename hostprogs-y/always to hostprogs/always-y	2020-02-04 01:53:07 +09:00
Kconfig	kbuild: ensure full rebuild when the compiler is updated	2020-05-12 13:28:33 +09:00
MAINTAINERS	f2fs: move ioctl interface definitions to separated file	2021-05-19 10:13:00 +02:00
Makefile	Linux 5.10.39	2021-05-22 11:40:55 +02:00
README	Drop all 00-INDEX files from Documentation/	2018-09-09 15:08:58 -06:00

README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.