tests/services: option to set stall threshold in RedpandaSettings

tests/rptest/services/redpanda.py

@@ -155,7 +155,8 @@ def __init__(self,
                  num_cpus: Optional[int] = None,
                  memory_mb: Optional[int] = None,
                  bypass_fsync: Optional[bool] = None,
-                 nfiles: Optional[int] = None):
+                 nfiles: Optional[int] = None,
+                 reactor_stall_threshold: Optional[int] = None):
         self._num_cpus = num_cpus
         self._memory_mb = memory_mb
 
@@ -165,6 +166,7 @@ def __init__(self,
             self._bypass_fsync = bypass_fsync
 
         self._nfiles = nfiles
+        self._reactor_stall_threshold = reactor_stall_threshold
 
     @property
     def memory_mb(self):
@@ -202,6 +204,11 @@ def to_cli(self, *, dedicated_node):
                 "--reserve-memory=0M"
             ])
 
+        if self._reactor_stall_threshold is not None:
+            args.extend([
+                f"--blocked-reactor-notify-ms={self._reactor_stall_threshold}"
+            ])
+
         if num_cpus is not None:
             args.append(f"--smp={num_cpus}")
         if memory_mb is not None: