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drm/i915: Don't count semaphore waits towards a stuck ring

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If we detect a ring is in a valid wait for another, just let it be.
Eventually it will either begin to progress again, or the entire system
will come grinding to a halt and then hangcheck will fire as soon as the
deadlock is detected.

This error was foretold by Ben in
commit 05407ff889
Author: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Date:   Thu May 30 09:04:29 2013 +0300

    drm/i915: detect hang using per ring hangcheck_score

"If ring B is waiting on ring A via semaphore, and ring A is making
progress, albeit slowly - the hangcheck will fire. The check will
determine that A is moving, however ring B will appear hung because
the ACTHD doesn't move. I honestly can't say if that's actually a
realistic problem to hit it probably implies the timeout value is too
low."

v2: Make sure we don't even incur the KICK cost whilst waiting.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=65394
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
This commit is contained in:
Chris Wilson 2013-06-10 11:20:21 +01:00 committed by Daniel Vetter
parent 9107e9d227
commit 6274f2126a
2 changed files with 88 additions and 30 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

117
drivers/gpu/drm/i915/i915_irq.c
View file

@ -2321,21 +2321,21 @@ ring_idle(struct intel_ring_buffer *ring, u32 seqno)
i915_seqno_passed(seqno, ring_last_seqno(ring)));
}
static bool semaphore_passed(struct intel_ring_buffer *ring)
static struct intel_ring_buffer *
semaphore_waits_for(struct intel_ring_buffer *ring, u32 *seqno)
{
struct drm_i915_private *dev_priv = ring->dev->dev_private;
u32 acthd = intel_ring_get_active_head(ring) & HEAD_ADDR;
struct intel_ring_buffer *signaller;
u32 cmd, ipehr, acthd_min;
u32 cmd, ipehr, acthd, acthd_min;
ipehr = I915_READ(RING_IPEHR(ring->mmio_base));
if ((ipehr & ~(0x3 << 16)) !=
(MI_SEMAPHORE_MBOX | MI_SEMAPHORE_COMPARE | MI_SEMAPHORE_REGISTER))
return false;
return NULL;
/* ACTHD is likely pointing to the dword after the actual command,
* so scan backwards until we find the MBOX.
*/
acthd = intel_ring_get_active_head(ring) & HEAD_ADDR;
acthd_min = max((int)acthd - 3 * 4, 0);
do {
cmd = ioread32(ring->virtual_start + acthd);
@ -2344,22 +2344,53 @@ static bool semaphore_passed(struct intel_ring_buffer *ring)
acthd -= 4;
if (acthd < acthd_min)
return false;
return NULL;
} while (1);
signaller = &dev_priv->ring[(ring->id + (((ipehr >> 17) & 1) + 1)) % 3];
return i915_seqno_passed(signaller->get_seqno(signaller, false),
ioread32(ring->virtual_start+acthd+4)+1);
*seqno = ioread32(ring->virtual_start+acthd+4)+1;
return &dev_priv->ring[(ring->id + (((ipehr >> 17) & 1) + 1)) % 3];
}
static bool ring_hung(struct intel_ring_buffer *ring)
static int semaphore_passed(struct intel_ring_buffer *ring)
{
struct drm_i915_private *dev_priv = ring->dev->dev_private;
struct intel_ring_buffer *signaller;
u32 seqno, ctl;
ring->hangcheck.deadlock = true;
signaller = semaphore_waits_for(ring, &seqno);
if (signaller == NULL || signaller->hangcheck.deadlock)
return -1;
/* cursory check for an unkickable deadlock */
ctl = I915_READ_CTL(signaller);
if (ctl & RING_WAIT_SEMAPHORE && semaphore_passed(signaller) < 0)
return -1;
return i915_seqno_passed(signaller->get_seqno(signaller, false), seqno);
}
static void semaphore_clear_deadlocks(struct drm_i915_private *dev_priv)
{
struct intel_ring_buffer *ring;
int i;
for_each_ring(ring, dev_priv, i)
ring->hangcheck.deadlock = false;
}
static enum { wait, active, kick, hung } ring_stuck(struct intel_ring_buffer *ring, u32 acthd)
{
struct drm_device *dev = ring->dev;
struct drm_i915_private *dev_priv = dev->dev_private;
u32 tmp;
if (ring->hangcheck.acthd != acthd)
return active;
if (IS_GEN2(dev))
return true;
return hung;
/* Is the chip hanging on a WAIT_FOR_EVENT?
* If so we can simply poke the RB_WAIT bit
@ -2371,19 +2402,24 @@ static bool ring_hung(struct intel_ring_buffer *ring)
DRM_ERROR("Kicking stuck wait on %s\n",
ring->name);
I915_WRITE_CTL(ring, tmp);
return false;
return kick;
}
if (INTEL_INFO(dev)->gen >= 6 &&
tmp & RING_WAIT_SEMAPHORE &&
semaphore_passed(ring)) {
DRM_ERROR("Kicking stuck semaphore on %s\n",
ring->name);
I915_WRITE_CTL(ring, tmp);
return false;
if (INTEL_INFO(dev)->gen >= 6 && tmp & RING_WAIT_SEMAPHORE) {
switch (semaphore_passed(ring)) {
default:
return hung;
case 1:
DRM_ERROR("Kicking stuck semaphore on %s\n",
ring->name);
I915_WRITE_CTL(ring, tmp);
return kick;
case 0:
return wait;
}
}
return true;
return hung;
}
/**
@ -2414,6 +2450,8 @@ void i915_hangcheck_elapsed(unsigned long data)
u32 seqno, acthd;
bool busy = true;
semaphore_clear_deadlocks(dev_priv);
seqno = ring->get_seqno(ring, false);
acthd = intel_ring_get_active_head(ring);
@ -2430,17 +2468,36 @@ void i915_hangcheck_elapsed(unsigned long data)
} else {
int score;
stuck[i] = ring->hangcheck.acthd == acthd;
if (stuck[i]) {
/* Every time we kick the ring, add a
* small increment to the hangcheck
* score so that we can catch a
* batch that is repeatedly kicked.
*/
score = ring_hung(ring) ? HUNG : KICK;
} else
/* We always increment the hangcheck score
* if the ring is busy and still processing
* the same request, so that no single request
* can run indefinitely (such as a chain of
* batches). The only time we do not increment
* the hangcheck score on this ring, if this
* ring is in a legitimate wait for another
* ring. In that case the waiting ring is a
* victim and we want to be sure we catch the
* right culprit. Then every time we do kick
* the ring, add a small increment to the
* score so that we can catch a batch that is
* being repeatedly kicked and so responsible
* for stalling the machine.
*/
switch (ring_stuck(ring, acthd)) {
case wait:
score = 0;
break;
case active:
score = BUSY;
break;
case kick:
score = KICK;
break;
case hung:
score = HUNG;
stuck[i] = true;
break;
}
ring->hangcheck.score += score;
}
} else {

1
drivers/gpu/drm/i915/intel_ringbuffer.h
View file

@ -38,6 +38,7 @@ struct intel_hw_status_page {
#define I915_READ_SYNC_1(ring) I915_READ(RING_SYNC_1((ring)->mmio_base))
struct intel_ring_hangcheck {
bool deadlock;
u32 seqno;
u32 acthd;
int score;