Since schedule-in and schedule-out are now both always under the tasklet bitlock, we can reduce the individual atomic operations to simple instructions and worry less.
This notably eliminates the race observed with intel_context_inflight in __engine_unpark(). Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2583 Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk> Reviewed-by: Tvrtko Ursulin <tvrtko.ursu...@intel.com> --- drivers/gpu/drm/i915/gt/intel_lrc.c | 52 ++++++++++++++--------------- 1 file changed, 25 insertions(+), 27 deletions(-) diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c index 5f90ecacc22b..d5bd537de9b7 100644 --- a/drivers/gpu/drm/i915/gt/intel_lrc.c +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c @@ -1331,11 +1331,11 @@ __execlists_schedule_in(struct i915_request *rq) ce->lrc.ccid = ce->tag; } else { /* We don't need a strict matching tag, just different values */ - unsigned int tag = ffs(READ_ONCE(engine->context_tag)); + unsigned int tag = __ffs(engine->context_tag); - GEM_BUG_ON(tag == 0 || tag >= BITS_PER_LONG); - clear_bit(tag - 1, &engine->context_tag); - ce->lrc.ccid = tag << (GEN11_SW_CTX_ID_SHIFT - 32); + GEM_BUG_ON(tag >= BITS_PER_LONG); + __clear_bit(tag, &engine->context_tag); + ce->lrc.ccid = (1 + tag) << (GEN11_SW_CTX_ID_SHIFT - 32); BUILD_BUG_ON(BITS_PER_LONG > GEN12_MAX_CONTEXT_HW_ID); } @@ -1348,6 +1348,8 @@ __execlists_schedule_in(struct i915_request *rq) execlists_context_status_change(rq, INTEL_CONTEXT_SCHEDULE_IN); intel_engine_context_in(engine); + CE_TRACE(ce, "schedule-in, ccid:%x\n", ce->lrc.ccid); + return engine; } @@ -1359,13 +1361,10 @@ static inline void execlists_schedule_in(struct i915_request *rq, int idx) GEM_BUG_ON(!intel_engine_pm_is_awake(rq->engine)); trace_i915_request_in(rq, idx); - old = READ_ONCE(ce->inflight); - do { - if (!old) { - WRITE_ONCE(ce->inflight, __execlists_schedule_in(rq)); - break; - } - } while (!try_cmpxchg(&ce->inflight, &old, ptr_inc(old))); + old = ce->inflight; + if (!old) + old = __execlists_schedule_in(rq); + WRITE_ONCE(ce->inflight, ptr_inc(old)); GEM_BUG_ON(intel_context_inflight(ce) != rq->engine); } @@ -1418,12 +1417,11 @@ static void kick_siblings(struct i915_request *rq, struct intel_context *ce) tasklet_hi_schedule(&ve->base.execlists.tasklet); } -static inline void -__execlists_schedule_out(struct i915_request *rq, - struct intel_engine_cs * const engine, - unsigned int ccid) +static inline void __execlists_schedule_out(struct i915_request *rq) { struct intel_context * const ce = rq->context; + struct intel_engine_cs * const engine = rq->engine; + unsigned int ccid; /* * NB process_csb() is not under the engine->active.lock and hence @@ -1431,6 +1429,8 @@ __execlists_schedule_out(struct i915_request *rq, * refrain from doing non-trivial work here. */ + CE_TRACE(ce, "schedule-out, ccid:%x\n", ce->lrc.ccid); + if (IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)) execlists_check_context(ce, engine, "after"); @@ -1442,12 +1442,13 @@ __execlists_schedule_out(struct i915_request *rq, i915_request_completed(rq)) intel_engine_add_retire(engine, ce->timeline); + ccid = ce->lrc.ccid; ccid >>= GEN11_SW_CTX_ID_SHIFT - 32; ccid &= GEN12_MAX_CONTEXT_HW_ID; if (ccid < BITS_PER_LONG) { GEM_BUG_ON(ccid == 0); GEM_BUG_ON(test_bit(ccid - 1, &engine->context_tag)); - set_bit(ccid - 1, &engine->context_tag); + __set_bit(ccid - 1, &engine->context_tag); } intel_context_update_runtime(ce); @@ -1468,26 +1469,23 @@ __execlists_schedule_out(struct i915_request *rq, */ if (ce->engine != engine) kick_siblings(rq, ce); - - intel_context_put(ce); } static inline void execlists_schedule_out(struct i915_request *rq) { struct intel_context * const ce = rq->context; - struct intel_engine_cs *cur, *old; - u32 ccid; trace_i915_request_out(rq); - ccid = rq->context->lrc.ccid; - old = READ_ONCE(ce->inflight); - do - cur = ptr_unmask_bits(old, 2) ? ptr_dec(old) : NULL; - while (!try_cmpxchg(&ce->inflight, &old, cur)); - if (!cur) - __execlists_schedule_out(rq, old, ccid); + GEM_BUG_ON(!ce->inflight); + ce->inflight = ptr_dec(ce->inflight); + if (!intel_context_inflight_count(ce)) { + GEM_BUG_ON(ce->inflight != rq->engine); + __execlists_schedule_out(rq); + WRITE_ONCE(ce->inflight, NULL); + intel_context_put(ce); + } i915_request_put(rq); } -- 2.20.1 _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
