/*
 * linux/kernel/irq/resend.c
 *
 * Copyright (C) 1992, 1998-2006 Linus Torvalds, Ingo Molnar
 * Copyright (C) 2005-2006, Thomas Gleixner
 *
 * This file contains the IRQ-resend code
 *
 * If the interrupt is waiting to be processed, we try to re-run it.
 * We can't directly run it from here since the caller might be in an
 * interrupt-protected region. Not all irq controller chips can
 * retrigger interrupts at the hardware level, so in those cases
 * we allow the resending of IRQs via a tasklet.
 */

#include <linux/irq.h>
#include <linux/module.h>
#include <linux/random.h>
#include <linux/interrupt.h>

#include "internals.h"

#ifdef CONFIG_HARDIRQS_SW_RESEND

/* Bitmap to handle software resend of interrupts: */
static DECLARE_BITMAP(irqs_resend, IRQ_BITMAP_BITS);

/*
 * Run software resends of IRQ's
 */
static void resend_irqs(unsigned long arg)
{
	struct irq_desc *desc;
	int irq;

	while (!bitmap_empty(irqs_resend, nr_irqs)) {
		irq = find_first_bit(irqs_resend, nr_irqs);
		clear_bit(irq, irqs_resend);
		desc = irq_to_desc(irq);
		local_irq_disable();
		desc->handle_irq(desc);
		local_irq_enable();
	}
}

/* Tasklet to handle resend: */
static DECLARE_TASKLET(resend_tasklet, resend_irqs, 0);

#endif

/*
 * IRQ resend
 *
 * Is called with interrupts disabled and desc->lock held.
 */
void check_irq_resend(struct irq_desc *desc)
{
	/*
	 * We do not resend level type interrupts. Level type
	 * interrupts are resent by hardware when they are still
	 * active. Clear the pending bit so suspend/resume does not
	 * get confused.
	 */
	if (irq_settings_is_level(desc)) {
		desc->istate &= ~IRQS_PENDING;
		return;
	}
	if (desc->istate & IRQS_REPLAY)
		return;
	if (desc->istate & IRQS_PENDING) {
		desc->istate &= ~IRQS_PENDING;
		desc->istate |= IRQS_REPLAY;

		if (!desc->irq_data.chip->irq_retrigger ||
		    !desc->irq_data.chip->irq_retrigger(&desc->irq_data)) {
#ifdef CONFIG_HARDIRQS_SW_RESEND
			unsigned int irq = irq_desc_get_irq(desc);

			/*
			 * If the interrupt is running in the thread
			 * context of the parent irq we need to be
			 * careful, because we cannot trigger it
			 * directly.
			 */
			if (irq_settings_is_nested_thread(desc)) {
				/*
				 * If the parent_irq is valid, we
				 * retrigger the parent, otherwise we
				 * do nothing.
				 */
				if (!desc->parent_irq)
					return;
				irq = desc->parent_irq;
			}
			/* Set it pending and activate the softirq: */
			set_bit(irq, irqs_resend);
			tasklet_schedule(&resend_tasklet);
#endif
		}
	}
}
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<div class='path'>path: <a href='/cgit.cgi/linux/net-next.git/diff/?id=d00b74613fb18dfd0a5aa99270ee2e72d5c808d7&amp;id2=3498c5e15db3af90aee7dbe9a0910225422b85c1'>root</a>/<a href='/cgit.cgi/linux/net-next.git/diff/net?id=d00b74613fb18dfd0a5aa99270ee2e72d5c808d7&amp;id2=3498c5e15db3af90aee7dbe9a0910225422b85c1'>net</a>/<a href='/cgit.cgi/linux/net-next.git/diff/net/irda?id=d00b74613fb18dfd0a5aa99270ee2e72d5c808d7&amp;id2=3498c5e15db3af90aee7dbe9a0910225422b85c1'>irda</a>/<a href='/cgit.cgi/linux/net-next.git/diff/net/irda/irlap.c?id=d00b74613fb18dfd0a5aa99270ee2e72d5c808d7&amp;id2=3498c5e15db3af90aee7dbe9a0910225422b85c1'>irlap.c</a></div><div class='content'><div class='cgit-panel'><b>diff options</b><form method='get'><input type='hidden' name='id' value='d00b74613fb18dfd0a5aa99270ee2e72d5c808d7'/><input type='hidden' name='id2' value='3498c5e15db3af90aee7dbe9a0910225422b85c1'/><table><tr><td colspan='2'/></tr><tr><td class='label'>context:</td><td class='ctrl'><select name='context' onchange='this.form.submit();'><option value='1'>1</option><option value='2'>2</option><option value='3' selected='selected'>3</option><option value='4'>4</option><option value='5'>5</option><option value='6'>6</option><option value='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><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?id=d00b74613fb18dfd0a5aa99270ee2e72d5c808d7&amp;id2=3498c5e15db3af90aee7dbe9a0910225422b85c1'>Diffstat</a> (limited to 'net/irda/irlap.c')</div><table summary='diffstat' class='diffstat'>a href='/cgit.cgi/linux/net-next.git/patch/sound/soc/codecs/da7219.h?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/sound/soc/codecs/da7219.h?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>sound/soc/codecs/da7219.h</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/sound/soc/codecs/da7219.h?id=2c5d9555d6d937966d79d4c6529a5f7b9206e405'>2c5d9555d6d937966d79d4c6529a5f7b9206e405</a> (<a href='/cgit.cgi/linux/net-next.git/diff/sound/soc/codecs/da7219.h?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 'sound/soc/codecs/da7219.h')</div><table summary='diffstat' class='diffstat'>