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Jens Axboe fcc926bb85 io_uring: add a conditional reschedule to the IOPOLL cancelation loop
If the kernel is configured with CONFIG_PREEMPT_NONE, we could be
sitting in a tight loop reaping events but not giving them a chance to
finish. This results in a trace ala:

rcu: INFO: rcu_sched self-detected stall on CPU
rcu: 	2-...!: (5249 ticks this GP) idle=935c/1/0x4000000000000000 softirq=4265/4274 fqs=1
	(t=5251 jiffies g=465 q=4135 ncpus=4)
rcu: rcu_sched kthread starved for 5249 jiffies! g465 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: 	Unless rcu_sched kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_sched       state:R  running task     stack:0     pid:12    ppid:2      flags:0x00000008
Call trace:
 __switch_to+0xb0/0xc8
 __schedule+0x43c/0x520
 schedule+0x4c/0x98
 schedule_timeout+0xbc/0xdc
 rcu_gp_fqs_loop+0x308/0x344
 rcu_gp_kthread+0xd8/0xf0
 kthread+0xb8/0xc8
 ret_from_fork+0x10/0x20
rcu: Stack dump where RCU GP kthread last ran:
Task dump for CPU 0:
task:kworker/u8:10   state:R  running task     stack:0     pid:89    ppid:2      flags:0x0000000a
Workqueue: events_unbound io_ring_exit_work
Call trace:
 __switch_to+0xb0/0xc8
 0xffff0000c8fefd28
CPU: 2 PID: 95 Comm: kworker/u8:13 Not tainted 6.2.0-rc5-00042-g40316e337c80-dirty #2759
Hardware name: linux,dummy-virt (DT)
Workqueue: events_unbound io_ring_exit_work
pstate: 61400005 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
pc : io_do_iopoll+0x344/0x360
lr : io_do_iopoll+0xb8/0x360
sp : ffff800009bebc60
x29: ffff800009bebc60 x28: 0000000000000000 x27: 0000000000000000
x26: ffff0000c0f67d48 x25: ffff0000c0f67840 x24: ffff800008950024
x23: 0000000000000001 x22: 0000000000000000 x21: ffff0000c27d3200
x20: ffff0000c0f67840 x19: ffff0000c0f67800 x18: 0000000000000000
x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
x14: 0000000000000001 x13: 0000000000000001 x12: 0000000000000000
x11: 0000000000000179 x10: 0000000000000870 x9 : ffff800009bebd60
x8 : ffff0000c27d3ad0 x7 : fefefefefefefeff x6 : 0000646e756f626e
x5 : ffff0000c0f67840 x4 : 0000000000000000 x3 : ffff0000c2398000
x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000000
Call trace:
 io_do_iopoll+0x344/0x360
 io_uring_try_cancel_requests+0x21c/0x334
 io_ring_exit_work+0x90/0x40c
 process_one_work+0x1a4/0x254
 worker_thread+0x1ec/0x258
 kthread+0xb8/0xc8
 ret_from_fork+0x10/0x20

Add a cond_resched() in the cancelation IOPOLL loop to fix this.

Cc: stable@vger.kernel.org # 5.10+
Signed-off-by: Jens Axboe <axboe@kernel.dk>
History 2023-01-29 15:17:41 -07:00
arch - Start checking for -mindirect-branch-cs-prefix clang support too now that LLVM 2023-01-29 11:17:34 -08:00
block block-6.2-2023-01-20 2023-01-20 12:44:41 -08:00
certs certs: make system keyring depend on built-in x509 parser 2022-09-24 04:31:18 +09:00
crypto This update includes the following changes: 2022-12-14 12:31:09 -08:00
Documentation - Start checking for -mindirect-branch-cs-prefix clang support too now that LLVM 2023-01-29 11:17:34 -08:00
drivers - Start checking for -mindirect-branch-cs-prefix clang support too now that LLVM 2023-01-29 11:17:34 -08:00
fs 4 smb3 server fixes, all also for stable 2023-01-28 10:52:51 -08:00
include io_uring: optimise ctx flags layout 2023-01-29 15:17:41 -07:00
init Kbuild fixes for v6.2 (3rd) 2023-01-21 10:56:37 -08:00
io_uring io_uring: add a conditional reschedule to the IOPOLL cancelation loop 2023-01-29 15:17:41 -07:00
ipc Non-MM patches for 6.2-rc1. 2022-12-12 17:28:58 -08:00
kernel - Cleanup the firmware node for the new IRQ MSI domain properly, to 2023-01-29 11:26:49 -08:00
lib hardening fixes for v6.2-rc6 2023-01-27 16:09:12 -08:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm Revert "mm/compaction: fix set skip in fast_find_migrateblock" 2023-01-29 10:38:43 -08:00
net net: mctp: mark socks as dead on unhash, prevent re-add 2023-01-25 13:07:37 +00:00
rust rust: print: avoid evaluating arguments in pr_* macros in unsafe blocks 2023-01-16 00:54:35 +01:00
samples ftrace: Export ftrace_free_filter() to modules 2023-01-24 11:20:58 -05:00
scripts Fix up more non-executable files marked executable 2023-01-28 11:17:57 -08:00
security tomoyo: Update website link 2023-01-13 23:11:38 +09:00
sound treewide: fix up files incorrectly marked executable 2023-01-26 10:05:39 -08:00
tools gpio fixes for v6.2-rc6 2023-01-27 13:47:40 -08:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt VFIO fixes for v6.2-rc6 2023-01-23 11:56:07 -08:00
.clang-format iommufd for 6.2 2022-12-14 09:15:43 -08:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore *.rpm 2022-12-30 17:22:14 +09:00
.mailmap 21 hotfixes. Thirteen of these address pre-6.1 issues and hence have 2023-01-16 16:36:39 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Update MPTCP maintainer list and CREDITS 2023-01-23 21:42:13 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Tracing updates for 6.2: 2023-01-27 16:03:32 -08:00
Makefile Linux 6.2-rc6 2023-01-29 13:59:43 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.