freebsd-dev/sys/dev/usb/usb_core.c
Hans Petter Selasky 0eb8d46232 Improve USB polling mode by not locking any mutexes, asserting any
mutexes or using any callouts when active.

Trying to lock a mutex when KDB is active or the scheduler is stopped
can result in infinite wait loops. The same goes for calling callout
related functions which in turn lock mutexes.

If the USB controller at which a USB keyboard is connected is idle
when KDB is entered, polling the USB keyboard via USB will always
succeed. Else polling may fail depending on which state the USB
subsystem and USB interrupt handler is in. This is unavoidable unless
KDB can wait for USB interrupt threads to complete before stalling the
CPU(s).

Tested by:	Bruce Evans <bde@freebsd.org>
MFC after:	4 weeks
2016-09-14 12:07:34 +00:00

82 lines
2.5 KiB
C

/* $FreeBSD$ */
/*-
* Copyright (c) 2008 Hans Petter Selasky. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* USB specifications and other documentation can be found at
* http://www.usb.org/developers/docs/ and
* http://www.usb.org/developers/devclass_docs/
*/
#ifdef USB_GLOBAL_INCLUDE_FILE
#include USB_GLOBAL_INCLUDE_FILE
#else
#include <sys/stdint.h>
#include <sys/stddef.h>
#include <sys/param.h>
#include <sys/queue.h>
#include <sys/types.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/bus.h>
#include <sys/module.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/condvar.h>
#include <sys/sysctl.h>
#include <sys/sx.h>
#include <sys/unistd.h>
#include <sys/callout.h>
#include <sys/malloc.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/kdb.h>
#include <dev/usb/usb.h>
#include <dev/usb/usbdi.h>
#endif /* USB_GLOBAL_INCLUDE_FILE */
const struct usb_string_lang usb_string_lang_en = {
sizeof(usb_string_lang_en), UDESC_STRING,
{ 0x09, 0x04 } /* American English */
};
MALLOC_DEFINE(M_USB, "USB", "USB");
MALLOC_DEFINE(M_USBDEV, "USBdev", "USB device");
int
usbd_in_polling_mode(void)
{
return (USB_IN_POLLING_MODE_VALUE());
}
void
usbd_dummy_timeout(void *arg)
{
/* NOP */
}
MODULE_VERSION(usb, 1);