---
- branch: MAIN
  date: Mon Mar 28 12:42:45 UTC 2022
  files:
  - new: '1.120'
    old: '1.119'
    path: src/sys/dev/usb/uhid.c
    pathrev: src/sys/dev/usb/uhid.c@1.120
    type: modified
  id: 20220328T124245Z.4ead6e12fe66f99f21f414ce609e0c37bc7224bb
  log: |
    uhid(4): Use d_cfdriver/devtounit/cancel to avoid open/detach races.

    - Split uhidclose into separate uhidcancel and uhidclose parts.
      uhidcancel interrupts pending I/O operations (open, read, write,
      ioctl, &c.); uhidclose doesn't run until all I/O operations are
      done.

    - Handle case where, owing to revoke(2), uhidcancel/uhidclose run
      concurrently with a uhidopen that hasn't yet noticed that there
      isn't actually a device.

    - Handle case where, owing to revoke(2), uhidread might be cancelled
      by mere revoke, not by detach, so it has to wake up when the device
      is closing, not (just) when dying (but dying will lead to closing
      so no need to check for dying).

    - Omit needless reference-counting goo.  vdevgone takes care of this
      for us by cancelling all I/O operations with uhidcancel, waiting
      for I/O operations to drain, closing the device, and waiting until
      it is closed if that is already happening concurrently.

    - Name the closed/changing/open states rather than using 0/1/2.

    - Omit needless sc_dying.
  module: src
  subject: 'CVS commit: src/sys/dev/usb'
  unixtime: '1648471365'
  user: riastradh