From: Chris Wilson <chris@chris-wilson.co.uk>
To: intel-gfx@lists.freedesktop.org
Subject: [Intel-gfx] [PATCH v2] drm/i915/gt: Defend against concurrent updates to execlists->active
Date: Mon, 9 Mar 2020 17:05:40 +0000 [thread overview]
Message-ID: <20200309170540.10332-1-chris@chris-wilson.co.uk> (raw)
In-Reply-To: <20200309112431.13903-1-chris@chris-wilson.co.uk>
[ 206.875637] BUG: KCSAN: data-race in __i915_schedule+0x7fc/0x930 [i915]
[ 206.875654]
[ 206.875666] race at unknown origin, with read to 0xffff8881f7644480 of 8 bytes by task 703 on cpu 3:
[ 206.875901] __i915_schedule+0x7fc/0x930 [i915]
[ 206.876130] __bump_priority+0x63/0x80 [i915]
[ 206.876361] __i915_sched_node_add_dependency+0x258/0x300 [i915]
[ 206.876593] i915_sched_node_add_dependency+0x50/0xa0 [i915]
[ 206.876824] i915_request_await_dma_fence+0x1da/0x530 [i915]
[ 206.877057] i915_request_await_object+0x2fe/0x470 [i915]
[ 206.877287] i915_gem_do_execbuffer+0x45dc/0x4c20 [i915]
[ 206.877517] i915_gem_execbuffer2_ioctl+0x2c3/0x580 [i915]
[ 206.877535] drm_ioctl_kernel+0xe4/0x120
[ 206.877549] drm_ioctl+0x297/0x4c7
[ 206.877563] ksys_ioctl+0x89/0xb0
[ 206.877577] __x64_sys_ioctl+0x42/0x60
[ 206.877591] do_syscall_64+0x6e/0x2c0
[ 206.877606] entry_SYSCALL_64_after_hwframe+0x44/0xa9
v2: Be safe and include mb
References: https://gitlab.freedesktop.org/drm/intel/issues/1318
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
---
drivers/gpu/drm/i915/gt/intel_engine.h | 15 ++++++++++++++-
drivers/gpu/drm/i915/gt/intel_lrc.c | 12 +++++++-----
2 files changed, 21 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/intel_engine.h b/drivers/gpu/drm/i915/gt/intel_engine.h
index 29c8c03c5caa..3644fd2b8877 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine.h
+++ b/drivers/gpu/drm/i915/gt/intel_engine.h
@@ -107,7 +107,20 @@ execlists_num_ports(const struct intel_engine_execlists * const execlists)
static inline struct i915_request *
execlists_active(const struct intel_engine_execlists *execlists)
{
- return *READ_ONCE(execlists->active);
+ struct i915_request * const *cur, * const *old, *active;
+
+ cur = READ_ONCE(execlists->active);
+ smp_rmb(); /* pairs with overwrite protection in process_csb() */
+ do {
+ old = cur;
+
+ active = READ_ONCE(*cur);
+ cur = READ_ONCE(execlists->active);
+
+ smp_rmb(); /* and complete the seqlock retry */
+ } while (cur != old);
+
+ return active;
}
static inline void
diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index 3eb7adc4e057..f4b7fdfa2d63 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -2389,6 +2389,7 @@ static void process_csb(struct intel_engine_cs *engine)
/* Point active to the new ELSP; prevent overwriting */
WRITE_ONCE(execlists->active, execlists->pending);
+ smp_wmb(); /* notify execlists_active() */
/* cancel old inflight, prepare for switch */
trace_ports(execlists, "preempted", old);
@@ -2396,11 +2397,12 @@ static void process_csb(struct intel_engine_cs *engine)
execlists_schedule_out(*old++);
/* switch pending to inflight */
- WRITE_ONCE(execlists->active,
- memcpy(execlists->inflight,
- execlists->pending,
- execlists_num_ports(execlists) *
- sizeof(*execlists->pending)));
+ memcpy(execlists->inflight,
+ execlists->pending,
+ execlists_num_ports(execlists) *
+ sizeof(*execlists->pending));
+ smp_wmb(); /* complete the seqlock */
+ WRITE_ONCE(execlists->active, execlists->inflight);
WRITE_ONCE(execlists->pending[0], NULL);
} else {
--
2.20.1
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next prev parent reply other threads:[~2020-03-09 17:06 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-09 11:24 [Intel-gfx] [PATCH] drm/i915/gt: Defend against concurrent updates to execlists->active Chris Wilson
2020-03-09 13:14 ` [Intel-gfx] ✓ Fi.CI.BAT: success for " Patchwork
2020-03-09 15:34 ` [Intel-gfx] [PATCH] " Mika Kuoppala
2020-03-09 16:19 ` Chris Wilson
2020-03-09 16:38 ` Mika Kuoppala
2020-03-09 17:01 ` Chris Wilson
2020-03-09 17:05 ` Chris Wilson [this message]
2020-03-09 17:41 ` [Intel-gfx] [PATCH v2] " Mika Kuoppala
2020-03-09 19:34 ` [Intel-gfx] ✓ Fi.CI.IGT: success for " Patchwork
2020-03-10 13:57 ` [Intel-gfx] ✗ Fi.CI.BUILD: failure for drm/i915/gt: Defend against concurrent updates to execlists->active (rev2) Patchwork
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