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drm/i915/gt: ce->inflight updates are now serialised

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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 <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201224135544.1713-9-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson 2020-12-24 13:55:44 +00:00
parent ac1a6d7310
commit 177b7a52a1
1 changed files with 25 additions and 27 deletions
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52
drivers/gpu/drm/i915/gt/intel_execlists_submission.c
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@ -524,11 +524,11 @@ __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);
}
@ -541,6 +541,8 @@ __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;
}
@ -552,13 +554,10 @@ 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);
}
@ -611,12 +610,11 @@ 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
@ -624,6 +622,8 @@ __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))
lrc_check_regs(ce, engine, "after");
@ -635,12 +635,13 @@ __execlists_schedule_out(struct i915_request *rq,
__i915_request_is_complete(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);
}
lrc_update_runtime(ce);
@ -661,26 +662,23 @@ __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->inflight)) {
GEM_BUG_ON(ce->inflight != rq->engine);
__execlists_schedule_out(rq);
WRITE_ONCE(ce->inflight, NULL);
intel_context_put(ce);
}
i915_request_put(rq);
}