rusticl/queue: fix implicit flushing of queue dependencies

Needed by Davinci Resolve.

There are two parts to this fix:
1. flush dependencies also on flush, not just finish
2. move the dependency checking logic into Queue::flush as otherwise we
   miss required implicit flushes.

Fixes: 8616c0a52c ("rusticl/event: flush queues from dependencies")
Signed-off-by: Karol Herbst <kherbst@redhat.com>
Reviewed-by: @LingMan <18294-LingMan@users.noreply.gitlab.freedesktop.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/26053>
(cherry picked from commit 8cbb84dc42)

.pick_status.json

@@ -44,7 +44,7 @@
         "description": "rusticl/queue: fix implicit flushing of queue dependencies",
         "nominated": true,
         "nomination_type": 1,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": "8616c0a52c776ecc7d0e946207ab35213b5ba985",
         "notes": null

src/gallium/frontends/rusticl/api/queue.rs

@@ -212,13 +212,7 @@ fn flush(command_queue: cl_command_queue) -> CLResult<()> {
 #[cl_entrypoint]
 fn finish(command_queue: cl_command_queue) -> CLResult<()> {
     // CL_INVALID_COMMAND_QUEUE if command_queue is not a valid host command-queue.
-    let q = command_queue.get_ref()?;
-
-    for q in q.dependencies_for_pending_events() {
-        q.flush(false)?;
-    }
-
-    q.flush(true)
+    command_queue.get_ref()?.flush(true)
 }
 
 #[cl_entrypoint]

src/gallium/frontends/rusticl/core/queue.rs

@@ -9,7 +9,6 @@ use mesa_rust::pipe::context::PipeContext;
 use mesa_rust_util::properties::*;
 use rusticl_opencl_gen::*;
 
-use std::collections::HashSet;
 use std::mem;
 use std::sync::mpsc;
 use std::sync::Arc;
@@ -133,6 +132,7 @@ impl Queue {
     pub fn flush(&self, wait: bool) -> CLResult<()> {
         let mut state = self.state.lock().unwrap();
         let events = mem::take(&mut state.pending);
+        let mut queues = Event::deep_unflushed_queues(&events);
 
         // Update last if and only if we get new events, this prevents breaking application code
         // doing things like `clFlush(q); clFinish(q);`
@@ -146,23 +146,28 @@ impl Queue {
                 .map_err(|_| CL_OUT_OF_HOST_MEMORY)?;
         }
 
-        if wait {
+        let last = wait.then(|| state.last.clone());
+
+        // We have to unlock before actually flushing otherwise we'll run into dead locks when a
+        // queue gets flushed concurrently.
+        drop(state);
+
+        // We need to flush out other queues implicitly and this _has_ to happen after taking the
+        // pending events, otherwise we'll risk dead locks when waiting on events.
+        queues.remove(self);
+        for q in queues {
+            q.flush(false)?;
+        }
+
+        if let Some(last) = last {
             // Waiting on the last event is good enough here as the queue will process it in order
             // It's not a problem if the weak ref is invalid as that means the work is already done
             // and waiting isn't necessary anymore.
-            state.last.upgrade().map(|e| e.wait());
+            last.upgrade().map(|e| e.wait());
         }
         Ok(())
     }
 
-    pub fn dependencies_for_pending_events(&self) -> HashSet<Arc<Queue>> {
-        let state = self.state.lock().unwrap();
-
-        let mut queues = Event::deep_unflushed_queues(&state.pending);
-        queues.remove(self);
-        queues
-    }
-
     pub fn is_profiling_enabled(&self) -> bool {
         (self.props & (CL_QUEUE_PROFILING_ENABLE as u64)) != 0
     }