e8b95728f7
Normally, when input device supporting force feedback effects is being destroyed, we try to "flush" currently playing effects, so that the physical device does not continue vibrating (or executing other effects). Unfortunately this does not work well for uinput as flushing of the effects deadlocks with the destroy action: - if device is being destroyed because the file descriptor is being closed, then there is noone to even service FF requests; - if device is being destroyed because userspace sent UI_DEV_DESTROY, while theoretically it could be possible to service FF requests, userspace is unlikely to do so (they'd need to make sure FF handling happens on a separate thread) even if kernel solves the issue with FF ioctls deadlocking with UI_DEV_DESTROY ioctl on udev->mutex. To avoid lockups like the one below, let's install a custom input device flush handler, and avoid trying to flush force feedback effects when we destroying the device, and instead rely on uinput to shut off the device properly. NMI watchdog: Watchdog detected hard LOCKUP on cpu 3 ... <<EOE>> [<ffffffff817a0307>] _raw_spin_lock_irqsave+0x37/0x40 [<ffffffff810e633d>] complete+0x1d/0x50 [<ffffffffa00ba08c>] uinput_request_done+0x3c/0x40 [uinput] [<ffffffffa00ba587>] uinput_request_submit.part.7+0x47/0xb0 [uinput] [<ffffffffa00bb62b>] uinput_dev_erase_effect+0x5b/0x76 [uinput] [<ffffffff815d91ad>] erase_effect+0xad/0xf0 [<ffffffff815d929d>] flush_effects+0x4d/0x90 [<ffffffff815d4cc0>] input_flush_device+0x40/0x60 [<ffffffff815daf1c>] evdev_cleanup+0xac/0xc0 [<ffffffff815daf5b>] evdev_disconnect+0x2b/0x60 [<ffffffff815d74ac>] __input_unregister_device+0xac/0x150 [<ffffffff815d75f7>] input_unregister_device+0x47/0x70 [<ffffffffa00bac45>] uinput_destroy_device+0xb5/0xc0 [uinput] [<ffffffffa00bb2de>] uinput_ioctl_handler.isra.9+0x65e/0x740 [uinput] [<ffffffff811231ab>] ? do_futex+0x12b/0xad0 [<ffffffffa00bb3f8>] uinput_ioctl+0x18/0x20 [uinput] [<ffffffff81241248>] do_vfs_ioctl+0x298/0x480 [<ffffffff81337553>] ? security_file_ioctl+0x43/0x60 [<ffffffff812414a9>] SyS_ioctl+0x79/0x90 [<ffffffff817a04ee>] entry_SYSCALL_64_fastpath+0x12/0x71 Reported-by: Rodrigo Rivas Costa <rodrigorivascosta@gmail.com> Reported-by: Clément VUCHENER <clement.vuchener@gmail.com> Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=193741 Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.