From edb76b01ac1629bfe17158bea56fcc16bfb57854 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Tue, 13 Feb 2018 09:57:44 +0000
Subject: [PATCH] drm/i915: Lock out execlist tasklet while peeking inside for busy-stats
Git-commit: edb76b01ac1629bfe17158bea56fcc16bfb57854
Patch-mainline: v4.16-rc2
No-fix: 99e48bf98dd036090b480a12c39e8b971731247e
References: FATE#322643 bsc#1055900
In order to prevent a race condition where we may end up overaccounting
the active state and leaving the busy-stats believing the GPU is 100%
busy, lock out the tasklet while we reconstruct the busy state. There is
no direct spinlock guard for the execlists->port[], so we need to
utilise tasklet_disable() as a synchronous barrier to prevent it, the
only writer to execlists->port[], from running at the same time as the
enable.
Fixes: 4900727d35bb ("drm/i915/pmu: Reconstruct active state on starting busy-stats")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180115092041.13509-1-chris@chris-wilson.co.uk
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
(cherry picked from commit 99e48bf98dd036090b480a12c39e8b971731247e)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180213095747.2424-1-tvrtko.ursulin@linux.intel.com
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/gpu/drm/i915/intel_engine_cs.c | 20 ++++++++++++--------
1 file changed, 12 insertions(+), 8 deletions(-)
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -1860,16 +1860,22 @@ void intel_engine_dump(struct intel_engi
*/
int intel_enable_engine_stats(struct intel_engine_cs *engine)
{
+ struct intel_engine_execlists *execlists = &engine->execlists;
unsigned long flags;
+ int err = 0;
if (!intel_engine_supports_stats(engine))
return -ENODEV;
+ tasklet_disable(&execlists->tasklet);
spin_lock_irqsave(&engine->stats.lock, flags);
- if (engine->stats.enabled == ~0)
- goto busy;
+
+ if (unlikely(engine->stats.enabled == ~0)) {
+ err = -EBUSY;
+ goto unlock;
+ }
+
if (engine->stats.enabled++ == 0) {
- struct intel_engine_execlists *execlists = &engine->execlists;
const struct execlist_port *port = execlists->port;
unsigned int num_ports = execlists_num_ports(execlists);
@@ -1884,14 +1890,12 @@ int intel_enable_engine_stats(struct int
if (engine->stats.active)
engine->stats.start = engine->stats.enabled_at;
}
- spin_unlock_irqrestore(&engine->stats.lock, flags);
-
- return 0;
-busy:
+unlock:
spin_unlock_irqrestore(&engine->stats.lock, flags);
+ tasklet_enable(&execlists->tasklet);
- return -EBUSY;
+ return err;
}
static ktime_t __intel_engine_get_busy_time(struct intel_engine_cs *engine)