On 09.01.24 06:50, David Stevens wrote:
On Tue, Jan 9, 2024 at 6:50 AM Theodore Ts'o <tytso@xxxxxxx> wrote:
Hi, while doing final testing before sending a pull request, I merged
in linux-next, and commit 5b9ce7ecd7: virtio_balloon: stay awake while
adjusting balloon seems to be causing a lockdep warning (see attached)
when running gce-xfstests on a Google Compute Engine e2 VM. I was not
able to trigger it using kvm-xfstests, but the following command:
"gce-xfstests -C 10 ext4/4k generic/476) was sufficient to triger the
problem. For more information please see [1] and [2].
[1] https://github.com/tytso/xfstests-bld/blob/master/Documentation/gce-xfstests.md
[2] https://thunk.org/gce-xfstests
I found it by looking at the git logs, and this commit aroused my
suspicions, and I further testing showed that the lockdep warning was
reproducible with this commit, but not when testing with the
immediately preceeding commit (15b9ce7ecd^).
Cheers,
- Ted
root: ext4/4k run xfstest generic/476
systemd[1]: Started fstests-generic-476.scope - /usr/bin/bash -c test -w /proc/self/oom_score_adj && echo 250 > /proc/self/oom_score_adj; exec ./tests/generic/476.
kernel: [ 399.361181] EXT4-fs (dm-1): mounted filesystem 840e25bd-f650-4819-8562-7eded85ef370 r/w with ordered data mode. Quota mode: none.
systemd[1]: fstests-generic-476.scope: Deactivated successfully.
systemd[1]: fstests-generic-476.scope: Consumed 3min 1.966s CPU time.
systemd[1]: xt\x2dvdb.mount: Deactivated successfully.
kernel: [ 537.085404] EXT4-fs (dm-0): unmounting filesystem d3d7a675-f7b6-4384-abec-2e60d885b6da.
systemd[1]: xt\x2dvdc.mount: Deactivated successfully.
kernel: [ 540.565870]
kernel: [ 540.567523] ================================
kernel: [ 540.572007] WARNING: inconsistent lock state
kernel: [ 540.576407] 6.7.0-rc3-xfstests-lockdep-00012-g5b9ce7ecd715 #318 Not tainted
kernel: [ 540.583532] --------------------------------
kernel: [ 540.587928] inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
kernel: [ 540.594326] kworker/0:3/329 [HC0[0]:SC0[0]:HE1:SE1] takes:
kernel: [ 540.599955] ffff90b280a548c0 (&vb->adjustment_lock){?...}-{2:2}, at: update_balloon_size_func+0x33/0x190
kernel: [ 540.609926] {IN-HARDIRQ-W} state was registered at:
kernel: [ 540.614935] __lock_acquire+0x3f2/0xb30
kernel: [ 540.618992] lock_acquire+0xbf/0x2b0
kernel: [ 540.622786] _raw_spin_lock_irqsave+0x43/0x90
kernel: [ 540.627366] virtballoon_changed+0x51/0xd0
kernel: [ 540.631947] virtio_config_changed+0x5a/0x70
kernel: [ 540.636437] vp_config_changed+0x11/0x20
kernel: [ 540.640576] __handle_irq_event_percpu+0x88/0x230
kernel: [ 540.645500] handle_irq_event+0x38/0x80
kernel: [ 540.649558] handle_edge_irq+0x8f/0x1f0
kernel: [ 540.653791] __common_interrupt+0x47/0xf0
kernel: [ 540.658106] common_interrupt+0x79/0xa0
kernel: [ 540.661672] EXT4-fs (dm-1): unmounting filesystem 840e25bd-f650-4819-8562-7eded85ef370.
kernel: [ 540.663183] asm_common_interrupt+0x26/0x40
kernel: [ 540.663190] acpi_safe_halt+0x1b/0x30
kernel: [ 540.663196] acpi_idle_enter+0x7b/0xd0
kernel: [ 540.663199] cpuidle_enter_state+0x90/0x4f0
kernel: [ 540.688723] cpuidle_enter+0x2d/0x40
kernel: [ 540.692516] cpuidle_idle_call+0xe4/0x120
kernel: [ 540.697036] do_idle+0x84/0xd0
kernel: [ 540.700393] cpu_startup_entry+0x2a/0x30
kernel: [ 540.704588] rest_init+0xe9/0x180
kernel: [ 540.708118] arch_call_rest_init+0xe/0x30
kernel: [ 540.712426] start_kernel+0x41c/0x4b0
kernel: [ 540.716310] x86_64_start_reservations+0x18/0x30
kernel: [ 540.721164] x86_64_start_kernel+0x8c/0x90
kernel: [ 540.725737] secondary_startup_64_no_verify+0x178/0x17b
kernel: [ 540.731432] irq event stamp: 22681
kernel: [ 540.734956] hardirqs last enabled at (22681): [<ffffffff8b4b5158>] _raw_spin_unlock_irq+0x28/0x50
kernel: [ 540.744564] hardirqs last disabled at (22680): [<ffffffff8b4b4ded>] _raw_spin_lock_irq+0x5d/0x90
kernel: [ 540.753475] softirqs last enabled at (22076): [<ffffffff8a58cfa1>] srcu_invoke_callbacks+0x101/0x1c0
kernel: [ 540.762904] softirqs last disabled at (22072): [<ffffffff8a58cfa1>] srcu_invoke_callbacks+0x101/0x1c0
kernel: [ 540.773298]
kernel: [ 540.773298] other info that might help us debug this:
kernel: [ 540.780207] Possible unsafe locking scenario:
kernel: [ 540.780207]
kernel: [ 540.786438] CPU0
kernel: [ 540.789007] ----
kernel: [ 540.791766] lock(&vb->adjustment_lock);
kernel: [ 540.796014] <Interrupt>
kernel: [ 540.798778] lock(&vb->adjustment_lock);
kernel: [ 540.803605]
Oh, that's embarrassing, I completely whiffed on interactions with
interrupts. The following patch fixes it, and I've locally repro'ed
the issue and verified the fix. What's the process for getting this
fix merged? Does it get merged as a seperatch patch, or squashed into
the original commit?
Depends on who queued it. Likely MST, so it can be squashed.
If it would be sitting in Andrews stable trees, we wouldn't be able to
squash it anymore.
From a99a1efa6a2b470a98ea2c87e58bebe90ce329a1 Mon Sep 17 00:00:00 2001
From: David Stevens <stevensd@xxxxxxxxxxxx>
Date: Tue, 9 Jan 2024 14:41:21 +0900
Subject: [PATCH] virtio_balloon: Fix interrupt context deadlock
Use _irq spinlock functions with the adjustment_lock, since
start_update_balloon_size needs to acquire it in an interrupt context.
Fixes: 5b9ce7ecd715 ("virtio_balloon: stay awake while adjusting balloon")
Reported-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: David Stevens <stevensd@xxxxxxxxxxxx>
---
drivers/virtio/virtio_balloon.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index aa6a1a649ad6..1f5b3dd31fcf 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -459,12 +459,12 @@ static void start_update_balloon_size(struct
virtio_balloon *vb)
static void end_update_balloon_size(struct virtio_balloon *vb)
{
- spin_lock(&vb->adjustment_lock);
+ spin_lock_irq(&vb->adjustment_lock);
if (!vb->adjustment_signal_pending && vb->adjustment_in_progress) {
vb->adjustment_in_progress = false;
pm_relax(vb->vdev->dev.parent);
}
- spin_unlock(&vb->adjustment_lock);
+ spin_unlock_irq(&vb->adjustment_lock);
}
static void virtballoon_changed(struct virtio_device *vdev)
@@ -506,9 +506,9 @@ static void update_balloon_size_func(struct
work_struct *work)
vb = container_of(work, struct virtio_balloon,
update_balloon_size_work);
- spin_lock(&vb->adjustment_lock);
+ spin_lock_irq(&vb->adjustment_lock);
vb->adjustment_signal_pending = false;
- spin_unlock(&vb->adjustment_lock);
+ spin_unlock_irq(&vb->adjustment_lock);
diff = towards_target(vb);
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
--
Cheers,
David / dhildenb
