Add a hang detector

drgn_tools/hang.py

@@ -0,0 +1,90 @@
+# Copyright (c) 2025, Oracle and/or its affiliates.
+# Licensed under the Universal Permissive License v 1.0 as shown at https://oss.oracle.com/licenses/upl/
+"""
+Help detect hang issues
+"""
+import argparse
+
+from drgn import Program
+from drgn.helpers.common import escape_ascii_string
+from drgn.helpers.linux.pid import for_each_task
+from drgn.helpers.linux.sched import task_state_to_char
+
+from drgn_tools.bt import bt
+from drgn_tools.corelens import CorelensModule
+from drgn_tools.task import task_lastrun2now
+from drgn_tools.util import timestamp_str
+
+
+def for_each_tasks_in_d_state(prog: Program):
+    for task in for_each_task(prog):
+        st = task_state_to_char(task)
+        if st != "D":
+            continue
+        yield task
+
+
+def detect_hang(prog: Program, stack: bool, time: int) -> None:
+    """
+    Scan hung tasks.
+
+    :param prog: drgn program
+    :param stack: bool
+    :param time: int
+    """
+    n_hung_tasks = 0
+    tasks = list(for_each_tasks_in_d_state(prog))
+    if not tasks:
+        print("There is no tasks in D state.")
+        return
+
+    tasks.sort(key=task_lastrun2now, reverse=True)
+    longest_hang_task = tasks[0]
+    longest_hang_time = task_lastrun2now(longest_hang_task) / 1e9
+    for task in tasks:
+        run_time = task_lastrun2now(task)
+        comm = escape_ascii_string(task.comm.string_())
+        pid = task.pid.value_()
+        prio = task.prio.value_()
+        if run_time / 1e9 > time:
+            n_hung_tasks += 1
+            print(
+                f"PID: {pid:<6d}  TASK: {task.value_():x}  PRIO: {prio}"
+                f'  COMMAND: "{comm}"'
+                f"  HUNG TIME: {timestamp_str(run_time)}",
+            )
+            if stack:
+                print("Calltrace:")
+                bt(task)
+                print()
+
+    print(
+        f"There are {n_hung_tasks} tasks hung (in D state) for more than {time} seconds as above."
+    )
+    print(
+        f"The longest hung task as below has remained in the D state for {longest_hang_time:.2f} seconds."
+    )
+    bt(longest_hang_task)
+
+
+class Hang(CorelensModule):
+    """Detectors for hang issues"""
+
+    name = "hang"
+
+    def add_args(self, parser: argparse.ArgumentParser) -> None:
+        parser.add_argument(
+            "--stack",
+            action="store_true",
+            help="Print the stacks. Only the stack of longest hung task is printed if not set.",
+        )
+        parser.add_argument(
+            "--time",
+            "-t",
+            type=float,
+            default=10,
+            help="list all the processes that have been hung more than <time> seconds",
+        )
+
+    def run(self, prog: Program, args: argparse.Namespace) -> None:
+        detect_hang(prog, args.stack, args.time)

tests/test_hang.py

@@ -0,0 +1,7 @@
+# Copyright (c) 2025, Oracle and/or its affiliates.
+# Licensed under the Universal Permissive License v 1.0 as shown at https://oss.oracle.com/licenses/upl/
+from drgn_tools import hang
+
+
+def test_hang(prog):
+    hang.detect_hang(prog, stack=True, time=10)