Add crs_eviction detector

drgn_tools/crs_eviction.py

@@ -0,0 +1,86 @@
+# 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 crs eviction issues
+"""
+import argparse
+from typing import Optional
+
+import drgn
+from drgn import ObjectAbsentError
+from drgn import Program
+from drgn.helpers.linux.sched import cpu_curr
+
+from drgn_tools.corelens import CorelensModule
+from drgn_tools.dentry import dentry_for_each_child
+from drgn_tools.dentry import dentry_is_negative
+from drgn_tools.file import __path_by_inode
+from drgn_tools.lockup import tasks_waiting_fsnotify
+from drgn_tools.lockup import tasks_waiting_rcu_gp
+from drgn_tools.lockup import tasks_waiting_spinlock
+from drgn_tools.task import get_pid
+
+
+def crs_eviction_waiting_for_rcu(prog: Program) -> None:
+    """Different types of issues related to rcu"""
+    if not tasks_waiting_rcu_gp(prog):
+        return
+
+    # spinlock contention issue
+    if tasks_waiting_spinlock(prog):
+        # due to fsnotify
+        frame_list = tasks_waiting_fsnotify(prog)
+        if frame_list:
+            for task, frame in frame_list:
+                if frame.name == "__fsnotify_update_child_dentry_flags":
+                    if "alias" in frame.locals():
+                        dentry = frame["alias"]
+                        try:
+                            path_name = __path_by_inode(dentry.d_inode)
+                            total_count = 0
+                            negative_count = 0
+                            for child in dentry_for_each_child(dentry):
+                                total_count += 1
+                                if dentry_is_negative(child):
+                                    negative_count += 1
+                        except ObjectAbsentError:
+                            continue
+
+                        print(
+                            "CRS eviction caused by spinlock contention due to fsnotify detected."
+                        )
+                        print(f"PID: {get_pid(task)}")
+                        print(f"Directory being iterated: {path_name}")
+                        print(f"Total dentries: {total_count}")
+                        print(f"Negative dentries: {negative_count}")
+                        if total_count:
+                            print(
+                                f"% Negative dentries: {negative_count / total_count:.2%}"
+                            )
+
+
+def panic_triggered_by_crs_eviction(prog: Program) -> Optional[drgn.Thread]:
+    # dectect panic triggered by crs eviction
+    try:
+        panic_thread = prog.crashed_thread()
+    except Exception:
+        pid = cpu_curr(prog, prog["crashing_cpu"]).pid.value_()
+        panic_thread = prog.thread(pid)
+    if panic_thread and panic_thread.name in {"cssdmonitor", "ocssd.bin"}:
+        return panic_thread
+    return None
+
+
+def scan_crs_eviction(prog: Program) -> None:
+    if panic_triggered_by_crs_eviction(prog):
+        # run a list of detectors
+        crs_eviction_waiting_for_rcu(prog)
+
+
+class CrsEviction(CorelensModule):
+    """Detectors for crs eviction related issues"""
+
+    name = "crs_eviction"
+
+    def run(self, prog: Program, args: argparse.Namespace) -> None:
+        scan_crs_eviction(prog)

tests/test_crs_eviction.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 crs_eviction
+
+
+def test_crs_eviction(prog):
+    crs_eviction.scan_crs_eviction(prog)