[SYCL] Fix calculation of unreleased events in a pool (#4730)

Before the change number of unreleased events was set to the maximum at
event pool creation and then only decremented at the moment when event
from the pool is released. This is not correct for the case when pool
is not completely full.
Patch fixes calculation of unreleased events in a pool.

Signed-off-by: Artur Gainullin <[email protected]>

Author: againull

sycl/plugins/level_zero/pi_level_zero.cpp

@@ -448,10 +448,11 @@ _pi_context::getFreeSlotInExistingOrNewPool(ze_event_pool_handle_t &Pool,
     ZE_CALL(zeEventPoolCreate, (ZeContext, &ZeEventPoolDesc, ZeDevices.size(),
                                 &ZeDevices[0], ZePool));
     NumEventsAvailableInEventPool[*ZePool] = MaxNumEventsPerPool - 1;
-    NumEventsUnreleasedInEventPool[*ZePool] = MaxNumEventsPerPool;
+    NumEventsUnreleasedInEventPool[*ZePool] = 1;
   } else {
     Index = MaxNumEventsPerPool - NumEventsAvailableInEventPool[*ZePool];
     --NumEventsAvailableInEventPool[*ZePool];
+    ++NumEventsUnreleasedInEventPool[*ZePool];
   }
   Pool = *ZePool;
   return PI_SUCCESS;
@@ -466,6 +467,8 @@ pi_result _pi_context::decrementUnreleasedEventsInPool(pi_event Event) {
 
   // Put the empty pool to the cache of the pools.
   std::lock_guard<std::mutex> Lock(ZeEventPoolCacheMutex);
+  if (NumEventsUnreleasedInEventPool[Event->ZeEventPool] == 0)
+    die("Invalid event release: event pool doesn't have unreleased events");
   if (--NumEventsUnreleasedInEventPool[Event->ZeEventPool] == 0) {
     if (ZeEventPoolCache.front() != Event->ZeEventPool) {
       ZeEventPoolCache.push_back(Event->ZeEventPool);
@@ -474,6 +477,9 @@ pi_result _pi_context::decrementUnreleasedEventsInPool(pi_event Event) {
   }
 
   if (Event->ZeHostVisibleEventPool) {
+    if (NumEventsUnreleasedInEventPool[Event->ZeEventPool] == 0)
+      die("Invalid host visible event release: host visible event pool doesn't "
+          "have unreleased events");
     if (--NumEventsUnreleasedInEventPool[Event->ZeHostVisibleEventPool] == 0) {
       if (ZeHostVisibleEventPoolCache.front() !=
           Event->ZeHostVisibleEventPool) {