On Tue, Apr 11, 2023 at 08:39:00AM +0200, Das, Nirmoy wrote:
On 3/8/2023 10:41 AM, Andi Shyti wrote:
Currently, when we perform operations such as clearing or copying large blocks of memory, we generate multiple requests that are executed in a chain.
However, if one of these requests fails, we may not realize it unless it happens to be the last request in the chain. This is because errors are not properly propagated.
For this we need to keep propagating the chain of fence notification in order to always reach the final fence associated to the final request.
To address this issue, we need to ensure that the chain of fence notifications is always propagated so that we can reach the final fence associated with the last request. By doing so, we will be able to detect any memory operation failures and determine whether the memory is still invalid.
On copy and clear migration signal fences upon completion.
On copy and clear migration, signal fences upon request completion to ensure that we have a reliable perpetuation of the operation outcome.
Fixes: cf586021642d80 ("drm/i915/gt: Pipelined page migration") Reported-by: Matthew Auld matthew.auld@intel.com Suggested-by: Chris Wilson chris@chris-wilson.co.uk Signed-off-by: Andi Shyti andi.shyti@linux.intel.com Cc: stable@vger.kernel.org Reviewed-by: Matthew Auld matthew.auld@intel.com
With Matt's comment regarding missing lock in intel_context_migrate_clear addressed, this is:
Acked-by: Nirmoy Das nirmoy.das@intel.com
Nack!
Please get some ack from Joonas or Tvrtko before merging this series.
It is a big series targeting stable o.O where the revisions in the cover letter are not helping me to be confident that this is the right approach instead of simply reverting the original offending commit:
cf586021642d ("drm/i915/gt: Pipelined page migration")
It looks to me that we are adding magic on top of magic to workaround the deadlocks, but then adding more waits inside locks... And this with the hang checks vs heartbeats, is this really an issue on current upstream code? or was only on DII?
Where was the bug report to start with?
drivers/gpu/drm/i915/gt/intel_migrate.c | 41 ++++++++++++++++++------- 1 file changed, 30 insertions(+), 11 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/intel_migrate.c b/drivers/gpu/drm/i915/gt/intel_migrate.c index 3f638f1987968..0031e7b1b4704 100644 --- a/drivers/gpu/drm/i915/gt/intel_migrate.c +++ b/drivers/gpu/drm/i915/gt/intel_migrate.c @@ -742,13 +742,19 @@ intel_context_migrate_copy(struct intel_context *ce, dst_offset = 2 * CHUNK_SZ; }
- /*
* While building the chain of requests, we need to ensure* that no one can sneak into the timeline unnoticed.*/- mutex_lock(&ce->timeline->mutex);
- do { int len;
rq = i915_request_create(ce);
rq = i915_request_create_locked(ce);
goto out_ce;
break;@@ -878,10 +884,14 @@ intel_context_migrate_copy(struct intel_context *ce, /* Arbitration is re-enabled between requests. */ out_rq:
if (*out)
i915_sw_fence_await(&rq->submit);i915_request_get(rq);i915_request_add_locked(rq);if (*out) {i915_sw_fence_complete(&(*out)->submit); i915_request_put(*out);
*out = i915_request_get(rq);i915_request_add(rq);
}*out = rq;@@ -905,7 +915,10 @@ intel_context_migrate_copy(struct intel_context *ce, cond_resched(); } while (1); -out_ce:
- mutex_unlock(&ce->timeline->mutex);
- if (*out)
i915_sw_fence_complete(&(*out)->submit);@@ -1005,7 +1018,7 @@ intel_context_migrate_clear(struct intel_context *ce, rq = i915_request_create(ce); if (IS_ERR(rq)) { err = PTR_ERR(rq);
goto out_ce;
break;@@ -1056,17 +1069,23 @@ intel_context_migrate_clear(struct intel_context *ce, /* Arbitration is re-enabled between requests. */ out_rq:
if (*out)i915_request_put(*out);*out = i915_request_get(rq);
i915_sw_fence_await(&rq->submit);i915_request_get(rq);if (*out) {i915_sw_fence_complete(&(*out)->submit);i915_request_put(*out);}*out = rq;- if (err || !it.sg || !sg_dma_len(it.sg)) break; cond_resched(); } while (1);
-out_ce:
- if (*out)
i915_sw_fence_complete(&(*out)->submit);