FAILED: patch "[PATCH] io_uring: add a conditional reschedule to the IOPOLL" failed to apply to 5.15-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x fcc926bb857949dbfa51a7d95f3f5ebc657f198c
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '1678099723159112@kroah.com' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

fcc926bb8579 ("io_uring: add a conditional reschedule to the IOPOLL cancelation loop")
affa87db9010 ("io_uring: fix multi ctx cancellation")
9ca9fb24d5fe ("io_uring: mutex locked poll hashing")
e6f89be61410 ("io_uring: introduce a struct for hash table")
a2cdd5193218 ("io_uring: pass hash table into poll_find")
0ec6dca22319 ("io_uring: use state completion infra for poll reqs")
8b1dfd343ae6 ("io_uring: clean up io_ring_ctx_alloc")
4a07723fb4bb ("io_uring: limit the number of cancellation buckets")
1ab1edb0a104 ("io_uring: pass poll_find lock back")
38513c464d3d ("io_uring: switch cancel_hash to use per entry spinlock")
aff5b2df9e8b ("io_uring: better caching for ctx timeout fields")
735729844819 ("io_uring: move rsrc related data, core, and commands")
3b77495a9723 ("io_uring: split provided buffers handling into its own file")
7aaff708a768 ("io_uring: move cancelation into its own file")
329061d3e2f9 ("io_uring: move poll handling into its own file")
cfd22e6b3319 ("io_uring: add opcode name to io_op_defs")
92ac8beaea1f ("io_uring: include and forward-declaration sanitation")
c9f06aa7de15 ("io_uring: move io_uring_task (tctx) helpers into its own file")
a4ad4f748ea9 ("io_uring: move fdinfo helpers to its own file")
e5550a1447bf ("io_uring: use io_is_uring_fops() consistently")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From fcc926bb857949dbfa51a7d95f3f5ebc657f198c Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Fri, 27 Jan 2023 09:28:13 -0700
Subject: [PATCH] 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>

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 9c92ca081c11..fab581a31dc1 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -3160,6 +3160,7 @@ static __cold bool io_uring_try_cancel_requests(struct io_ring_ctx *ctx,
 		while (!wq_list_empty(&ctx->iopoll_list)) {
 			io_iopoll_try_reap_events(ctx);
 			ret = true;
+			cond_resched();
 		}
 	}