| Message ID | 20191123110330.874616-1-chris@chris-wilson.co.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/i915/gt: Mark the execlists->active as the primary volatile access | expand |
diff --git a/drivers/gpu/drm/i915/gt/intel_engine.h b/drivers/gpu/drm/i915/gt/intel_engine.h index bc3b72bfa9e3..7f3cd84982b1 100644 --- a/drivers/gpu/drm/i915/gt/intel_engine.h +++ b/drivers/gpu/drm/i915/gt/intel_engine.h @@ -102,7 +102,7 @@ execlists_active(const struct intel_engine_execlists *execlists) { GEM_BUG_ON(execlists->active - execlists->inflight > execlists_num_ports(execlists)); - return READ_ONCE(*execlists->active); + return *READ_ONCE(execlists->active); } static inline void
Since we want to do a lockless read of the current active request, and that request is written to by process_csb also without serialisation, we need to instruct gcc to take care in reading the pointer itself. Otherwise, we have observed execlists_active() to report 0x40. [ 2400.760381] igt/para-4098 1..s. 2376479300us : process_csb: rcs0 cs-irq head=3, tail=4 [ 2400.760826] igt/para-4098 1..s. 2376479303us : process_csb: rcs0 csb[4]: status=0x00000001:0x00000000 [ 2400.761271] igt/para-4098 1..s. 2376479306us : trace_ports: rcs0: promote { b9c59:2622, b9c55:2624 } [ 2400.761726] igt/para-4097 0d... 2376479311us : __i915_schedule: rcs0: -2147483648->3, inflight:0000000000000040, rq:ffff888208c1e940 which is impossible! Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> --- drivers/gpu/drm/i915/gt/intel_engine.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)