The breadcrumbs are about to be used from within IRQ context sections
(e.g. nouveau signals a fence from an interrupt handler causing us to
submit a new request) and/or from bottom-half tasklets (i.e.
intel_lrc_irq_handler), therefore we need to employ the irqsafe spinlock
variants.
For example, deferring the request submission to the
intel_lrc_irq_handler generates this trace:
[ 66.388639] =================================
[ 66.388650] [ INFO: inconsistent lock state ]
[ 66.388663] 4.9.0-rc2+ #56 Not tainted
[ 66.388672] ---------------------------------
[ 66.388682] inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
[ 66.388695] swapper/1/0 [HC0[0]:SC1[1]:HE0:SE0] takes:
[ 66.388706] (&(&b->lock)->rlock){+.?...} , at: [<ffffffff81401c88>] intel_engine_enable_signaling+0x78/0x150
[ 66.388761] {SOFTIRQ-ON-W} state was registered at:
[ 66.388772] [ 66.388783] [<ffffffff810bd842>] __lock_acquire+0x682/0x1870
[ 66.388795] [ 66.388803] [<ffffffff810bedbc>] lock_acquire+0x6c/0xb0
[ 66.388814] [ 66.388824] [<ffffffff8161753a>] _raw_spin_lock+0x2a/0x40
[ 66.388835] [ 66.388845] [<ffffffff81401e41>] intel_engine_reset_breadcrumbs+0x21/0xb0
[ 66.388857] [ 66.388866] [<ffffffff81403ae7>] gen8_init_common_ring+0x67/0x100
[ 66.388878] [ 66.388887] [<ffffffff81403b92>] gen8_init_render_ring+0x12/0x60
[ 66.388903] [ 66.388912] [<ffffffff813f8707>] i915_gem_init_hw+0xf7/0x2a0
[ 66.388927] [ 66.388936] [<ffffffff813f899b>] i915_gem_init+0xbb/0xf0
[ 66.388950] [ 66.388959] [<ffffffff813b4980>] i915_driver_load+0x7e0/0x1330
[ 66.388978] [ 66.388988] [<ffffffff813c09d8>] i915_pci_probe+0x28/0x40
[ 66.389003] [ 66.389013] [<ffffffff812fa0db>] pci_device_probe+0x8b/0xf0
[ 66.389028] [ 66.389037] [<ffffffff8147737e>] driver_probe_device+0x21e/0x430
[ 66.389056] [ 66.389065] [<ffffffff8147766e>] __driver_attach+0xde/0xe0
[ 66.389080] [ 66.389090] [<ffffffff814751ad>] bus_for_each_dev+0x5d/0x90
[ 66.389105] [ 66.389113] [<ffffffff81477799>] driver_attach+0x19/0x20
[ 66.389134] [ 66.389144] [<ffffffff81475ced>] bus_add_driver+0x15d/0x260
[ 66.389159] [ 66.389168] [<ffffffff81477e3b>] driver_register+0x5b/0xd0
[ 66.389183] [ 66.389281] [<ffffffff812fa19b>] __pci_register_driver+0x5b/0x60
[ 66.389301] [ 66.389312] [<ffffffff81aed333>] i915_init+0x3e/0x45
[ 66.389326] [ 66.389336] [<ffffffff81ac2ffa>] do_one_initcall+0x8b/0x118
[ 66.389350] [ 66.389359] [<ffffffff81ac323a>] kernel_init_freeable+0x1b3/0x23b
[ 66.389378] [ 66.389387] [<ffffffff8160fc39>] kernel_init+0x9/0x100
[ 66.389402] [ 66.389411] [<ffffffff816180e7>] ret_from_fork+0x27/0x40
[ 66.389426] irq event stamp: 315865
[ 66.389438] hardirqs last enabled at (315864): [<ffffffff816178f1>] _raw_spin_unlock_irqrestore+0x31/0x50
[ 66.389469] hardirqs last disabled at (315865): [<ffffffff816176b3>] _raw_spin_lock_irqsave+0x13/0x50
[ 66.389499] softirqs last enabled at (315818): [<ffffffff8107a04c>] _local_bh_enable+0x1c/0x50
[ 66.389530] softirqs last disabled at (315819): [<ffffffff8107a50e>] irq_exit+0xbe/0xd0
[ 66.389559]
[ 66.389559] other info that might help us debug this:
[ 66.389580] Possible unsafe locking scenario:
[ 66.389580]
[ 66.389598] CPU0
[ 66.389609] ----
[ 66.389620] lock(&(&b->lock)->rlock);
[ 66.389650] <Interrupt>
[ 66.389661] lock(&(&b->lock)->rlock);
[ 66.389690]
[ 66.389690] *** DEADLOCK ***
[ 66.389690]
[ 66.389715] 2 locks held by swapper/1/0:
[ 66.389728] #0: (&(&tl->lock)->rlock){..-...}, at: [<ffffffff81403e01>] intel_lrc_irq_handler+0x201/0x3c0
[ 66.389785] #1: (&(&req->lock)->rlock/1){..-...}, at: [<ffffffff813fc0af>] __i915_gem_request_submit+0x8f/0x170
[ 66.389854]
[ 66.389854] stack backtrace:
[ 66.389959] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.9.0-rc2+ #56
[ 66.389976] Hardware name: / , BIOS PYBSWCEL.86A.0027.2015.0507.1758 05/07/2015
[ 66.389999] ffff88027fd03c58 ffffffff812beae5 ffff88027696e680 ffffffff822afe20
[ 66.390036] ffff88027fd03ca8 ffffffff810bb420 0000000000000001 0000000000000000
[ 66.390070] 0000000000000000 0000000000000006 0000000000000004 ffff88027696ee10
[ 66.390104] Call Trace:
[ 66.390117] <IRQ>
[ 66.390128] [<ffffffff812beae5>] dump_stack+0x68/0x93
[ 66.390147] [<ffffffff810bb420>] print_usage_bug+0x1d0/0x1e0
[ 66.390164] [<ffffffff810bb8a0>] mark_lock+0x470/0x4f0
[ 66.390181] [<ffffffff810ba9d0>] ? print_shortest_lock_dependencies+0x1b0/0x1b0
[ 66.390203] [<ffffffff810bd75d>] __lock_acquire+0x59d/0x1870
[ 66.390221] [<ffffffff810bedbc>] lock_acquire+0x6c/0xb0
[ 66.390237] [<ffffffff810bedbc>] ? lock_acquire+0x6c/0xb0
[ 66.390255] [<ffffffff81401c88>] ? intel_engine_enable_signaling+0x78/0x150
[ 66.390273] [<ffffffff8161753a>] _raw_spin_lock+0x2a/0x40
[ 66.390291] [<ffffffff81401c88>] ? intel_engine_enable_signaling+0x78/0x150
[ 66.390309] [<ffffffff81401c88>] intel_engine_enable_signaling+0x78/0x150
[ 66.390327] [<ffffffff813fc170>] __i915_gem_request_submit+0x150/0x170
[ 66.390345] [<ffffffff81403e8b>] intel_lrc_irq_handler+0x28b/0x3c0
[ 66.390363] [<ffffffff81079d97>] tasklet_action+0x57/0xc0
[ 66.390380] [<ffffffff8107a249>] __do_softirq+0x119/0x240
[ 66.390396] [<ffffffff8107a50e>] irq_exit+0xbe/0xd0
[ 66.390414] [<ffffffff8101afd5>] do_IRQ+0x65/0x110
[ 66.390431] [<ffffffff81618806>] common_interrupt+0x86/0x86
[ 66.390446] <EOI>
[ 66.390457] [<ffffffff814ec6d1>] ? cpuidle_enter_state+0x151/0x200
[ 66.390480] [<ffffffff814ec7a2>] cpuidle_enter+0x12/0x20
[ 66.390498] [<ffffffff810b639e>] call_cpuidle+0x1e/0x40
[ 66.390516] [<ffffffff810b65ae>] cpu_startup_entry+0x10e/0x1f0
[ 66.390534] [<ffffffff81036133>] start_secondary+0x103/0x130
(This is split out of the defer global seqno allocation patch due to
realisation that we need a more complete conversion if we want to defer
request submission even further.)
v2: lockdep was warning about mixed SOFTIRQ contexts not HARDIRQ
contexts so we only need to use spin_lock_bh and not disable interrupts.
v3: We need full irq protection as we may be called from a third party
interrupt handler (via fences).
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_debugfs.c | 12 +++++------
drivers/gpu/drm/i915/i915_gpu_error.c | 8 ++++----
drivers/gpu/drm/i915/intel_breadcrumbs.c | 35 ++++++++++++++++++++------------
drivers/gpu/drm/i915/intel_ringbuffer.h | 2 +-
4 files changed, 33 insertions(+), 24 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index a60803c4f11a..a2fa445fe409 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -683,14 +683,14 @@ static void i915_ring_seqno_info(struct seq_file *m,
seq_printf(m, "Current sequence (%s): %x\n",
engine->name, intel_engine_get_seqno(engine));
- spin_lock(&b->lock);
+ spin_lock_irq(&b->lock);
for (rb = rb_first(&b->waiters); rb; rb = rb_next(rb)) {
struct intel_wait *w = container_of(rb, typeof(*w), node);
seq_printf(m, "Waiting (%s): %s [%d] on %x\n",
engine->name, w->tsk->comm, w->tsk->pid, w->seqno);
}
- spin_unlock(&b->lock);
+ spin_unlock_irq(&b->lock);
}
static int i915_gem_seqno_info(struct seq_file *m, void *data)
@@ -1355,14 +1355,14 @@ static int i915_hangcheck_info(struct seq_file *m, void *unused)
yesno(intel_engine_has_waiter(engine)),
yesno(test_bit(engine->id,
&dev_priv->gpu_error.missed_irq_rings)));
- spin_lock(&b->lock);
+ spin_lock_irq(&b->lock);
for (rb = rb_first(&b->waiters); rb; rb = rb_next(rb)) {
struct intel_wait *w = container_of(rb, typeof(*w), node);
seq_printf(m, "\t%s [%d] waiting for %x\n",
w->tsk->comm, w->tsk->pid, w->seqno);
}
- spin_unlock(&b->lock);
+ spin_unlock_irq(&b->lock);
seq_printf(m, "\tACTHD = 0x%08llx [current 0x%08llx]\n",
(long long)engine->hangcheck.acthd,
@@ -3265,14 +3265,14 @@ static int i915_engine_info(struct seq_file *m, void *unused)
I915_READ(RING_PP_DIR_DCLV(engine)));
}
- spin_lock(&b->lock);
+ spin_lock_irq(&b->lock);
for (rb = rb_first(&b->waiters); rb; rb = rb_next(rb)) {
struct intel_wait *w = container_of(rb, typeof(*w), node);
seq_printf(m, "\t%s [%d] waiting for %x\n",
w->tsk->comm, w->tsk->pid, w->seqno);
}
- spin_unlock(&b->lock);
+ spin_unlock_irq(&b->lock);
seq_puts(m, "\n");
}
diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
index ef3698120d92..7ba40487e345 100644
--- a/drivers/gpu/drm/i915/i915_gpu_error.c
+++ b/drivers/gpu/drm/i915/i915_gpu_error.c
@@ -1043,7 +1043,7 @@ static void error_record_engine_waiters(struct intel_engine_cs *engine,
if (RB_EMPTY_ROOT(&b->waiters))
return;
- if (!spin_trylock(&b->lock)) {
+ if (!spin_trylock_irq(&b->lock)) {
ee->waiters = ERR_PTR(-EDEADLK);
return;
}
@@ -1051,7 +1051,7 @@ static void error_record_engine_waiters(struct intel_engine_cs *engine,
count = 0;
for (rb = rb_first(&b->waiters); rb != NULL; rb = rb_next(rb))
count++;
- spin_unlock(&b->lock);
+ spin_unlock_irq(&b->lock);
waiter = NULL;
if (count)
@@ -1061,7 +1061,7 @@ static void error_record_engine_waiters(struct intel_engine_cs *engine,
if (!waiter)
return;
- if (!spin_trylock(&b->lock)) {
+ if (!spin_trylock_irq(&b->lock)) {
kfree(waiter);
ee->waiters = ERR_PTR(-EDEADLK);
return;
@@ -1079,7 +1079,7 @@ static void error_record_engine_waiters(struct intel_engine_cs *engine,
if (++ee->num_waiters == count)
break;
}
- spin_unlock(&b->lock);
+ spin_unlock_irq(&b->lock);
}
static void error_record_engine_registers(struct drm_i915_error_state *error,
diff --git a/drivers/gpu/drm/i915/intel_breadcrumbs.c b/drivers/gpu/drm/i915/intel_breadcrumbs.c
index 0d5def0d2dfe..c410d3d6465f 100644
--- a/drivers/gpu/drm/i915/intel_breadcrumbs.c
+++ b/drivers/gpu/drm/i915/intel_breadcrumbs.c
@@ -83,16 +83,18 @@ static void irq_enable(struct intel_engine_cs *engine)
*/
engine->breadcrumbs.irq_posted = true;
- spin_lock_irq(&engine->i915->irq_lock);
+ /* Caller disables interrupts */
+ spin_lock(&engine->i915->irq_lock);
engine->irq_enable(engine);
- spin_unlock_irq(&engine->i915->irq_lock);
+ spin_unlock(&engine->i915->irq_lock);
}
static void irq_disable(struct intel_engine_cs *engine)
{
- spin_lock_irq(&engine->i915->irq_lock);
+ /* Caller disables interrupts */
+ spin_lock(&engine->i915->irq_lock);
engine->irq_disable(engine);
- spin_unlock_irq(&engine->i915->irq_lock);
+ spin_unlock(&engine->i915->irq_lock);
engine->breadcrumbs.irq_posted = false;
}
@@ -293,9 +295,9 @@ bool intel_engine_add_wait(struct intel_engine_cs *engine,
struct intel_breadcrumbs *b = &engine->breadcrumbs;
bool first;
- spin_lock(&b->lock);
+ spin_lock_irq(&b->lock);
first = __intel_engine_add_wait(engine, wait);
- spin_unlock(&b->lock);
+ spin_unlock_irq(&b->lock);
return first;
}
@@ -326,7 +328,7 @@ void intel_engine_remove_wait(struct intel_engine_cs *engine,
if (RB_EMPTY_NODE(&wait->node))
return;
- spin_lock(&b->lock);
+ spin_lock_irq(&b->lock);
if (RB_EMPTY_NODE(&wait->node))
goto out_unlock;
@@ -400,7 +402,7 @@ void intel_engine_remove_wait(struct intel_engine_cs *engine,
GEM_BUG_ON(rb_first(&b->waiters) !=
(b->first_wait ? &b->first_wait->node : NULL));
GEM_BUG_ON(!rcu_access_pointer(b->irq_seqno_bh) ^ RB_EMPTY_ROOT(&b->waiters));
- spin_unlock(&b->lock);
+ spin_unlock_irq(&b->lock);
}
static bool signal_complete(struct drm_i915_gem_request *request)
@@ -473,14 +475,14 @@ static int intel_breadcrumbs_signaler(void *arg)
* we just completed - so double check we are still
* the oldest before picking the next one.
*/
- spin_lock(&b->lock);
+ spin_lock_irq(&b->lock);
if (request == b->first_signal) {
struct rb_node *rb =
rb_next(&request->signaling.node);
b->first_signal = rb ? to_signaler(rb) : NULL;
}
rb_erase(&request->signaling.node, &b->signals);
- spin_unlock(&b->lock);
+ spin_unlock_irq(&b->lock);
i915_gem_request_put(request);
} else {
@@ -502,7 +504,14 @@ void intel_engine_enable_signaling(struct drm_i915_gem_request *request)
struct rb_node *parent, **p;
bool first, wakeup;
- /* locked by dma_fence_enable_sw_signaling() */
+ /* Note that we may be called from an interrupt handler on another
+ * device (e.g. nouveau signaling a fence completion causing us
+ * to submit a request, and so enable signaling). As such,
+ * we need to make sure that all other users of b->lock protect
+ * against interrupts, i.e. use spin_lock_irqsave.
+ */
+
+ /* locked by dma_fence_enable_sw_signaling() (irqsafe fence->lock) */
assert_spin_locked(&request->lock);
if (!request->global_seqno)
return;
@@ -594,7 +603,7 @@ void intel_engine_reset_breadcrumbs(struct intel_engine_cs *engine)
struct intel_breadcrumbs *b = &engine->breadcrumbs;
cancel_fake_irq(engine);
- spin_lock(&b->lock);
+ spin_lock_irq(&b->lock);
__intel_breadcrumbs_disable_irq(b);
if (intel_engine_has_waiter(engine)) {
@@ -607,7 +616,7 @@ void intel_engine_reset_breadcrumbs(struct intel_engine_cs *engine)
irq_disable(engine);
}
- spin_unlock(&b->lock);
+ spin_unlock_irq(&b->lock);
}
void intel_engine_fini_breadcrumbs(struct intel_engine_cs *engine)
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 891629caab6c..d16c74ae8f54 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -207,7 +207,7 @@ struct intel_engine_cs {
struct task_struct __rcu *irq_seqno_bh; /* bh for interrupts */
bool irq_posted;
- spinlock_t lock; /* protects the lists of requests */
+ spinlock_t lock; /* protects the lists of requests; irqsafe */
struct rb_root waiters; /* sorted by retirement, priority */
struct rb_root signals; /* sorted by retirement */
struct intel_wait *first_wait; /* oldest waiter by retirement */
--
2.10.1
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