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
References: bsc#1012628
Patch-mainline: 6.2.3
Git-commit: fcc926bb857949dbfa51a7d95f3f5ebc657f198c
commit fcc926bb857949dbfa51a7d95f3f5ebc657f198c upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
io_uring/io_uring.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index fbeb9d21..d7e2a743 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -3053,6 +3053,7 @@ 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();
}
}
--
2.35.3