Commit 712da5fc authored Oct 28, 2020 by Mathias Nyman Committed by Greg Kroah-Hartman Oct 29, 2020

xhci: Don't create stream debugfs files with spinlock held.



Creating debugfs files while loding the spin_lock_irqsave(xhci->lock)
creates a lock dependecy that could possibly deadlock.

Lockdep warns:

=====================================================
WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected
5.10.0-rc1pdx86+ #8 Not tainted
-----------------------------------------------------
systemd-udevd/386 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
ffffffffb1a94038 (pin_fs_lock){+.+.}-{2:2}, at: simple_pin_fs+0x22/0xa0

and this task is already holding:
ffff9e7b87fbc430 (&xhci->lock){-.-.}-{2:2}, at: xhci_alloc_streams+0x5f9/0x810
which would create a new lock dependency:
(&xhci->lock){-.-.}-{2:2} -> (pin_fs_lock){+.+.}-{2:2}

Create the files a bit later after lock is released.

Fixes: 673d7468 ("usb: xhci: add debugfs support for ep with stream")
CC: Li Jun <jun.li@nxp.com>
Reported-by: Hans de Goede <hdegoede@redhat.com>
Reported-by: Mike Galbraith <efault@gmx.de>
Tested-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20201028203124.375344-4-mathias.nyman@linux.intel.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 2a632815

drivers/usb/host/xhci.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -3533,11 +3533,14 @@ 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++) {
		ep_index = xhci_get_endpoint_index(&eps[i]->desc);
		xhci_debugfs_create_stream_files(xhci, vdev, ep_index);
		}
		/* Subtract 1 for stream 0, which drivers can't use */
		return num_streams - 1;

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