Re: [PATCH 3/3] xhci: Don't create stream debugfs files with spinlock held.

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Mathias Nyman <mathias.nyman@linux.intel.com>
Cc: Mike Galbraith <efault@gmx.de>,
	gregkh@linuxfoundation.org, linux-usb@vger.kernel.org,
	Hans de Goede <hdegoede@redhat.com>, Li Jun <jun.li@nxp.com>
Subject: Re: [PATCH 3/3] xhci: Don't create stream debugfs files with spinlock held.
Date: Thu, 29 Oct 2020 12:38:05 +0100	[thread overview]
Message-ID: <20201029113805.tdsissnjq4acemle@linutronix.de> (raw)
In-Reply-To: <a5d5a21c-d6ff-1097-b9ca-e0147658c8c6@linux.intel.com>

On 2020-10-29 13:22:20 [+0200], Mathias Nyman wrote:
> On 29.10.2020 13.11, Mike Galbraith wrote:
> > On Thu, 2020-10-29 at 11:41 +0200, Mathias Nyman wrote:
> >> Can you check if this can be reproduced with 5.9 kernel?
> > 
> > Nope, 5.9.2 didn't reproduce.
> > 
> 
> Very odd.
> It might be hard to reproduce as it requires xhci ring expansion to trigger it,
> meaning at some point there is so much data queued to a device the current ring buffer
> can't fit it.
> 
> Other possibility is that there were some radix tree changes in 5.10-rc1, haven't looked into those.

This came with commit
   673d74683627b ("usb: xhci: add debugfs support for ep with stream")

which is appeared in v5.10-rc1. This hunk below works around it:

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 482fe8c5e3b47..699777fb523b6 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -3533,11 +3533,13 @@ static int xhci_alloc_streams(struct usb_hcd *hcd, struct usb_device *udev,
 		xhci_dbg(xhci, "Slot %u ep ctx %u now has streams.\n",
 			 udev->slot_id, ep_index);
 		vdev->eps[ep_index].ep_state |= EP_HAS_STREAMS;
-		xhci_debugfs_create_stream_files(xhci, vdev, ep_index);
 	}
 	xhci_free_command(xhci, config_cmd);
 	spin_unlock_irqrestore(&xhci->lock, flags);
 
+	for (i = 0; i < num_eps; i++)
+		xhci_debugfs_create_stream_files(xhci, vdev, ep_index);
+
 	/* Subtract 1 for stream 0, which drivers can't use */
 	return num_streams - 1;
 
This makes the warning go away here, I'm not 100% sure that this okay.
One thing I noticed: free_streams() does not remove the debugfs file so:
| $ cd /sys/bus/usb/drivers/uas
| $ echo 2-1:1.0 > bind
| $ echo 2-1:1.0 > unbind

and the kernel log shows:
|sd 7:0:0:0: [sdb] Synchronizing SCSI cache
|sd 7:0:0:0: [sdb] Synchronize Cache(10) failed: Result: hostbyte=DID_ERROR driverbyte=DRIVER_OK
|debugfs: File 'stream_id' in directory 'ep07' already present!
|debugfs: File 'stream_context_array' in directory 'ep07' already present!
|debugfs: File 'stream_id' in directory 'ep07' already present!
|debugfs: File 'stream_context_array' in directory 'ep07' already present!
|scsi host7: uas
|scsi 7:0:0:0: Direct-Access     QEMU     QEMU HARDDISK    2.5+ PQ: 0 ANSI: 5
|sd 7:0:0:0: Attached scsi generic sg2 type 0
|sd 7:0:0:0: [sdb] 262144 512-byte logical blocks: (134 MB/128 MiB)
|sd 7:0:0:0: [sdb] Write Protect is off
|sd 7:0:0:0: [sdb] Mode Sense: 63 00 00 08
|sd 7:0:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
|sd 7:0:0:0: [sdb] Attached SCSI disk

> -Mathias

Sebastian
