Error msg: Device 'virtio0' does not have a release() function

[liuyuan10]

[ 13.000000] ------------[ cut here ]------------
[ 13.000000] WARNING: CPU: 0 PID: 40 at drivers/base/core.c:251 device_release+0x92/0xa0
[ 13.000000] Device 'virtio0' does not have a release() function, it is broken and must be fixed.
[ 13.000000] Call Trace:
[ 13.000000] 00007fccc97f99d8: [<7fcce725e0c2>] device_release+0x92/0xa0
[ 13.000000] 00007fccc97f99f8: [<7fcce6fc0c9a>] __warn+0xca/0xf0
[ 13.000000] 00007fccc97f9a48: [<7fcce6fc0d50>] warn_slowpath_fmt+0x90/0xa0
[ 13.000000] 00007fccc97f9a98: [<7fcce706f1c9>] kernfs_put+0x109/0x1d0
[ 13.000000] 00007fccc97f9ab8: [<7fcce72659c8>] release_nodes+0x1b8/0x230
[ 13.000000] 00007fccc97f9ad0: [<7fcce706f1c9>] kernfs_put+0x109/0x1d0
[ 13.000000] 00007fccc97f9b08: [<7fcce7265e4c>] devres_release_all+0x3c/0x60
[ 13.000000] 00007fccc97f9b28: [<7fcce725e0c2>] device_release+0x92/0xa0
[ 13.000000] 00007fccc97f9b58: [<7fcce722a26c>] kobject_cleanup+0x3c/0x80
[ 13.000000] 00007fccc97f9b88: [<7fcce722a18a>] kobject_put+0x4a/0x80
[ 13.000000] 00007fccc97f9bb8: [<7fcce725ec52>] put_device+0x12/0x20
[ 13.000000] 00007fccc97f9bc8: [<7fcce725f519>] device_unregister+0x19/0x20
[ 13.000000] 00007fccc97f9be8: [<7fcce72498c5>] unregister_virtio_device+0x15/0x30
[ 13.000000] 00007fccc97f9c08: [<7fcce724aef0>] virtio_mmio_remove+0x10/0x20
[ 13.000000] 00007fccc97f9c18: [<7fcce72640cf>] platform_drv_remove+0x1f/0x30
[ 13.000000] 00007fccc97f9c28: [<7fcce72630d9>] __device_release_driver+0x79/0x120
[ 13.000000] 00007fccc97f9c48: [<7fcce72631de>] device_release_driver+0x1e/0x30
[ 13.000000] 00007fccc97f9c68: [<7fcce7261365>] unbind_store+0xb5/0xe0
[ 13.000000] 00007fccc97f9cb8: [<7fcce7260c7f>] drv_attr_store+0x1f/0x30
[ 13.000000] 00007fccc97f9cc8: [<7fcce7071475>] sysfs_kf_write+0x35/0x50
[ 13.000000] 00007fccc97f9cd8: [<7fcce7070816>] kernfs_fop_write+0xa6/0x190
[ 13.000000] 00007fccc97f9ce8: [<7fcce7030577>] do_filp_open+0x87/0xd0
[ 13.000000] 00007fccc97f9d28: [<7fcce7023db5>] __vfs_write+0x25/0x160
[ 13.000000] 00007fccc97f9d68: [<7fcce7248bbe>] atomic64_add_unless+0x3e/0x60
[ 13.000000] 00007fccc97f9dc8: [<7fcce7023fd6>] vfs_write+0x86/0x100
[ 13.000000] 00007fccc97f9e18: [<7fcce7024155>] SyS_write+0x45/0xc0
[ 13.000000] 00007fccc97f9e68: [<7fcce6fbe010>] syscall_thread+0x1e0/0x380
[ 13.000000] 00007fccc97f9e90: [<7fcce6fe0a90>] autoremove_wake_function+0x0/0x40
[ 13.000000] 00007fccc97f9ea8: [<7fcce6fbde30>] syscall_thread+0x0/0x380
[ 13.000000] 00007fccc97f9ec8: [<7fcce6fbde30>] syscall_thread+0x0/0x380
[ 13.000000] 00007fccc97f9ee8: [<7fcce6fbd2e8>] thread_bootstrap+0x48/0x50

How to reproduce:
LKL_HIJACK_DEBUG=1 sh tests/run_netperf.sh

Looks like this is a know issue from comment in PR #241. @M1cha do you have any idea of this?

[M1cha]

@liuyuan10 I only know how to silence it, but not how to fix it, since I'm not that familiar with writing kernel platform drivers.

[M1cha]

@tavip shouldn't we report this to the linux kernel mailing list so they can fix it?

[liuyuan10]

I sent an one-line fix to upstream. Hopefully I won't get kicked :)

[M1cha]

can you post a mail archive link here for reference?

[liuyuan10]

I sent the mail to virtualization@lists.linux-foundation.org but can't find a archive link with my mail. Here is the mail I sent

From: Yuan Liu <liuyuan@google.com>

Fix a warning thrown from virtio_mmio_remove():
Device 'virtio0' does not have a release() function

The fix is according to virtio_pci_probe() of
drivers/virtio/virtio_pci_common.c

Signed-off-by: Yuan Liu <liuyuan@google.com>
---
 drivers/virtio/virtio_mmio.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
index 48bfea9..d47a2fc 100644
--- a/drivers/virtio/virtio_mmio.c
+++ b/drivers/virtio/virtio_mmio.c
@@ -489,6 +489,7 @@ static const struct virtio_config_ops virtio_mmio_config_ops = {
 };


+static void virtio_mmio_release_dev_empty(struct device *_d) {}

 /* Platform device */

@@ -511,6 +512,7 @@ static int virtio_mmio_probe(struct platform_device *pdev)
                return  -ENOMEM;

        vm_dev->vdev.dev.parent = &pdev->dev;
+       vm_dev->vdev.dev.release = virtio_mmio_release_dev_empty;
        vm_dev->vdev.config = &virtio_mmio_config_ops;
        vm_dev->pdev = pdev;
        INIT_LIST_HEAD(&vm_dev->virtqueues);

[liuyuan10]

Looks like this link only includes mails sent by the maintainer:
http://virtualization.linux-foundation.narkive.com/cJ0R9zlc/patch-virtio-mmio-set-dev-release-to-avoid-warning

[liuyuan10]

The fix has been merged to linux upstream:
torvalds@cecdbdc

[M1cha]

the patch will be in 4.10 then ( we didn't even merge 4.9 yet :D )

[thehajime]

I'm about to submit a pr on 4.9 merge. FYI.

[thehajime]

Fixed by #335.
(I was expected to close this issue by b485d40 but seems not to be automatically closed, dunno why.)

Thanks @liuyuan10 for the upstream !!