The patch below does not apply to the 5.10-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-5.10.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 '167809972215341@kroah.com' --subject-prefix 'PATCH 5.10.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(); } }