/*
 * Linux WiMAX
 * Implement and export a method for resetting a WiMAX device
 *
 *
 * Copyright (C) 2008 Intel Corporation <linux-wimax@intel.com>
 * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version
 * 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 *
 * This implements a simple synchronous call to reset a WiMAX device.
 *
 * Resets aim at being warm, keeping the device handles active;
 * however, when that fails, it falls back to a cold reset (that will
 * disconnect and reconnect the device).
 */

#include <net/wimax.h>
#include <net/genetlink.h>
#include <linux/wimax.h>
#include <linux/security.h>
#include <linux/export.h>
#include "wimax-internal.h"

#define D_SUBMODULE op_reset
#include "debug-levels.h"


/**
 * wimax_reset - Reset a WiMAX device
 *
 * @wimax_dev: WiMAX device descriptor
 *
 * Returns:
 *
 * %0 if ok and a warm reset was done (the device still exists in
 * the system).
 *
 * -%ENODEV if a cold/bus reset had to be done (device has
 * disconnected and reconnected, so current handle is not valid
 * any more).
 *
 * -%EINVAL if the device is not even registered.
 *
 * Any other negative error code shall be considered as
 * non-recoverable.
 *
 * Description:
 *
 * Called when wanting to reset the device for any reason. Device is
 * taken back to power on status.
 *
 * This call blocks; on successful return, the device has completed the
 * reset process and is ready to operate.
 */
int wimax_reset(struct wimax_dev *wimax_dev)
{
	int result = -EINVAL;
	struct device *dev = wimax_dev_to_dev(wimax_dev);
	enum wimax_st state;

	might_sleep();
	d_fnstart(3, dev, "(wimax_dev %p)\n", wimax_dev);
	mutex_lock(&wimax_dev->mutex);
	dev_hold(wimax_dev->net_dev);
	state = wimax_dev->state;
	mutex_unlock(&wimax_dev->mutex);

	if (state >= WIMAX_ST_DOWN) {
		mutex_lock(&wimax_dev->mutex_reset);
		result = wimax_dev->op_reset(wimax_dev);
		mutex_unlock(&wimax_dev->mutex_reset);
	}
	dev_put(wimax_dev->net_dev);

	d_fnend(3, dev, "(wimax_dev %p) = %d\n", wimax_dev, result);
	return result;
}
EXPORT_SYMBOL(wimax_reset);


/*
 * Exporting to user space over generic netlink
 *
 * Parse the reset command from user space, return error code.
 *
 * No attributes.
 */
int wimax_gnl_doit_reset(struct sk_buff *skb, struct genl_info *info)
{
	int result, ifindex;
	struct wimax_dev *wimax_dev;

	d_fnstart(3, NULL, "(skb %p info %p)\n", skb, info);
	result = -ENODEV;
	if (info->attrs[WIMAX_GNL_RESET_IFIDX] == NULL) {
		pr_err("WIMAX_GNL_OP_RFKILL: can't find IFIDX attribute\n");
		goto error_no_wimax_dev;
	}
	ifindex = nla_get_u32(info->attrs[WIMAX_GNL_RESET_IFIDX]);
	wimax_dev = wimax_dev_get_by_genl_info(info, ifindex);
	if (wimax_dev == NULL)
		goto error_no_wimax_dev;
	/* Execute the operation and send the result back to user space */
	result = wimax_reset(wimax_dev);
	dev_put(wimax_dev->net_dev);
error_no_wimax_dev:
	d_fnend(3, NULL, "(skb %p info %p) = %d\n", skb, info, result);
	return result;
}
alue='7'>7</option><option value='8'>8</option><option value='9'>9</option><option value='10'>10</option><option value='15'>15</option><option value='20'>20</option><option value='25'>25</option><option value='30'>30</option><option value='35'>35</option><option value='40'>40</option></select></td></tr><tr><td class='label'>space:</td><td class='ctrl'><select name='ignorews' onchange='this.form.submit();'><option value='0' selected='selected'>include</option><option value='1'>ignore</option></select></td></tr><tr><td class='label'>mode:</td><td class='ctrl'><select name='dt' onchange='this.form.submit();'><option value='0' selected='selected'>unified</option><option value='1'>ssdiff</option><option value='2'>stat only</option></select></td></tr><tr><td/><td class='ctrl'><noscript><input type='submit' value='reload'/></noscript></td></tr></table></form></div><table summary='commit info' class='commit-info'>
<tr><th>author</th><td>Linus Torvalds &lt;torvalds@linux-foundation.org&gt;</td><td class='right'>2017-01-29 13:50:06 -0800</td></tr>
<tr><th>committer</th><td>Linus Torvalds &lt;torvalds@linux-foundation.org&gt;</td><td class='right'>2017-01-29 13:50:06 -0800</td></tr>
<tr><th>commit</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/include/soc/nps?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>39cb2c9a316e77f6dfba96c543e55b6672d5a37e</a> (<a href='/cgit.cgi/linux/net-next.git/patch/include/soc/nps?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>patch</a>)</td></tr>
<tr><th>tree</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/tree/?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>98fe974ee4e20121253de7f61fc8d01bdb3821c1</a> /<a href='/cgit.cgi/linux/net-next.git/tree/include/soc/nps?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>include/soc/nps</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/include/soc/nps?id=2c5d9555d6d937966d79d4c6529a5f7b9206e405'>2c5d9555d6d937966d79d4c6529a5f7b9206e405</a> (<a href='/cgit.cgi/linux/net-next.git/diff/include/soc/nps?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e&amp;id2=2c5d9555d6d937966d79d4c6529a5f7b9206e405'>diff</a>)</td></tr></table>
<div class='commit-subject'>drm/i915: Check for NULL i915_vma in intel_unpin_fb_obj()</div><div class='commit-msg'>I've seen this trigger twice now, where the i915_gem_object_to_ggtt()
call in intel_unpin_fb_obj() returns NULL, resulting in an oops
immediately afterwards as the (inlined) call to i915_vma_unpin_fence()
tries to dereference it.

It seems to be some race condition where the object is going away at
shutdown time, since both times happened when shutting down the X
server.  The call chains were different:

 - VT ioctl(KDSETMODE, KD_TEXT):

    intel_cleanup_plane_fb+0x5b/0xa0 [i915]
    drm_atomic_helper_cleanup_planes+0x6f/0x90 [drm_kms_helper]
    intel_atomic_commit_tail+0x749/0xfe0 [i915]
    intel_atomic_commit+0x3cb/0x4f0 [i915]
    drm_atomic_commit+0x4b/0x50 [drm]
    restore_fbdev_mode+0x14c/0x2a0 [drm_kms_helper]
    drm_fb_helper_restore_fbdev_mode_unlocked+0x34/0x80 [drm_kms_helper]
    drm_fb_helper_set_par+0x2d/0x60 [drm_kms_helper]
    intel_fbdev_set_par+0x18/0x70 [i915]
    fb_set_var+0x236/0x460
    fbcon_blank+0x30f/0x350
    do_unblank_screen+0xd2/0x1a0
    vt_ioctl+0x507/0x12a0
    tty_ioctl+0x355/0xc30
    do_vfs_ioctl+0xa3/0x5e0
    SyS_ioctl+0x79/0x90
    entry_SYSCALL_64_fastpath+0x13/0x94

 - i915 unpin_work workqueue:

    intel_unpin_work_fn+0x58/0x140 [i915]
    process_one_work+0x1f1/0x480
    worker_thread+0x48/0x4d0
    kthread+0x101/0x140

and this patch purely papers over the issue by adding a NULL pointer
check and a WARN_ON_ONCE() to avoid the oops that would then generally
make the machine unresponsive.

Other callers of i915_gem_object_to_ggtt() seem to also check for the
returned pointer being NULL and warn about it, so this clearly has
happened before in other places.

[ Reported it originally to the i915 developers on Jan 8, applying the
  ugly workaround on my own now after triggering the problem for the
  second time with no feedback.

  This is likely to be the same bug reported as

     https://bugs.freedesktop.org/show_bug.cgi?id=98829
     https://bugs.freedesktop.org/show_bug.cgi?id=99134

  which has a patch for the underlying problem, but it hasn't gotten to
  me, so I'm applying the workaround. ]

Cc: Daniel Vetter &lt;daniel.vetter@intel.com&gt;
Cc: Jani Nikula &lt;jani.nikula@linux.intel.com&gt;
Cc: Ville Syrjälä &lt;ville.syrjala@linux.intel.com&gt;
Cc: Chris Wilson &lt;chris@chris-wilson.co.uk&gt;
Cc: Maarten Lankhorst &lt;maarten.lankhorst@linux.intel.com&gt;
Cc: Tvrtko Ursulin &lt;tvrtko.ursulin@intel.com&gt;
Cc: Imre Deak &lt;imre.deak@intel.com&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>Diffstat</a> (limited to 'include/soc/nps')</div><table summary='diffstat' class='diffstat'>