Merge tag 'wq-for-6.5' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq

Pull workqueue updates from Tejun Heo:

 - Concurrency-managed per-cpu work items that hog CPUs and delay the
   execution of other work items are now automatically detected and
   excluded from concurrency management. Reporting on such work items
   can also be enabled through a config option.

 - Added tools/workqueue/wq_monitor.py which improves visibility into
   workqueue usages and behaviors.

 - Arnd's minimal fix for gcc-13 enum warning on 32bit compiles,
   superseded by commit afa4bb778e48 in mainline.

* tag 'wq-for-6.5' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
  workqueue: Disable per-cpu CPU hog detection when wq_cpu_intensive_thresh_us is 0
  workqueue: Fix WARN_ON_ONCE() triggers in worker_enter_idle()
  workqueue: fix enum type for gcc-13
  workqueue: Track and monitor per-workqueue CPU time usage
  workqueue: Report work funcs that trigger automatic CPU_INTENSIVE mechanism
  workqueue: Automatically mark CPU-hogging work items CPU_INTENSIVE
  workqueue: Improve locking rule description for worker fields
  workqueue: Move worker_set/clr_flags() upwards
  workqueue: Re-order struct worker fields
  workqueue: Add pwq->stats[] and a monitoring script
  Further upgrade queue_work_on() comment

1 files changed, 168 insertions, 0 deletions

diff --git a/tools/workqueue/wq_monitor.py b/tools/workqueue/wq_monitor.py
new file mode 100644
index 000000000000..6e258d123e8c
--- /dev/null
+++ b/tools/workqueue/wq_monitor.py
@@ -0,0 +1,168 @@
+#!/usr/bin/env drgn
+#
+# Copyright (C) 2023 Tejun Heo <tj@kernel.org>
+# Copyright (C) 2023 Meta Platforms, Inc. and affiliates.
+
+desc = """
+This is a drgn script to monitor workqueues. For more info on drgn, visit
+https://github.com/osandov/drgn.
+
+  total    Total number of work items executed by the workqueue.
+
+  infl     The number of currently in-flight work items.
+
+  CPUtime  Total CPU time consumed by the workqueue in seconds. This is
+           sampled from scheduler ticks and only provides ballpark
+           measurement. "nohz_full=" CPUs are excluded from measurement.
+
+  CPUitsv  The number of times a concurrency-managed work item hogged CPU
+           longer than the threshold (workqueue.cpu_intensive_thresh_us)
+           and got excluded from concurrency management to avoid stalling
+           other work items.
+
+  CMwake   The number of concurrency-management wake-ups while executing a
+           work item of the workqueue.
+
+  mayday   The number of times the rescuer was requested while waiting for
+           new worker creation.
+
+  rescued  The number of work items executed by the rescuer.
+"""
+
+import sys
+import signal
+import os
+import re
+import time
+import json
+
+import drgn
+from drgn.helpers.linux.list import list_for_each_entry,list_empty
+from drgn.helpers.linux.cpumask import for_each_possible_cpu
+
+import argparse
+parser = argparse.ArgumentParser(description=desc,
+                                 formatter_class=argparse.RawTextHelpFormatter)
+parser.add_argument('workqueue', metavar='REGEX', nargs='*',
+                    help='Target workqueue name patterns (all if empty)')
+parser.add_argument('-i', '--interval', metavar='SECS', type=float, default=1,
+                    help='Monitoring interval (0 to print once and exit)')
+parser.add_argument('-j', '--json', action='store_true',
+                    help='Output in json')
+args = parser.parse_args()
+
+def err(s):
+    print(s, file=sys.stderr, flush=True)
+    sys.exit(1)
+
+workqueues              = prog['workqueues']
+
+WQ_UNBOUND              = prog['WQ_UNBOUND']
+WQ_MEM_RECLAIM          = prog['WQ_MEM_RECLAIM']
+
+PWQ_STAT_STARTED        = prog['PWQ_STAT_STARTED']      # work items started execution
+PWQ_STAT_COMPLETED      = prog['PWQ_STAT_COMPLETED']	# work items completed execution
+PWQ_STAT_CPU_TIME       = prog['PWQ_STAT_CPU_TIME']     # total CPU time consumed
+PWQ_STAT_CPU_INTENSIVE  = prog['PWQ_STAT_CPU_INTENSIVE'] # wq_cpu_intensive_thresh_us violations
+PWQ_STAT_CM_WAKEUP      = prog['PWQ_STAT_CM_WAKEUP']    # concurrency-management worker wakeups
+PWQ_STAT_MAYDAY         = prog['PWQ_STAT_MAYDAY']	# maydays to rescuer
+PWQ_STAT_RESCUED        = prog['PWQ_STAT_RESCUED']	# linked work items executed by rescuer
+PWQ_NR_STATS            = prog['PWQ_NR_STATS']
+
+class WqStats:
+    def __init__(self, wq):
+        self.name = wq.name.string_().decode()
+        self.unbound = wq.flags & WQ_UNBOUND != 0
+        self.mem_reclaim = wq.flags & WQ_MEM_RECLAIM != 0
+        self.stats = [0] * PWQ_NR_STATS
+        for pwq in list_for_each_entry('struct pool_workqueue', wq.pwqs.address_of_(), 'pwqs_node'):
+            for i in range(PWQ_NR_STATS):
+                self.stats[i] += int(pwq.stats[i])
+
+    def dict(self, now):
+        return { 'timestamp'            : now,
+                 'name'                 : self.name,
+                 'unbound'              : self.unbound,
+                 'mem_reclaim'          : self.mem_reclaim,
+                 'started'              : self.stats[PWQ_STAT_STARTED],
+                 'completed'            : self.stats[PWQ_STAT_COMPLETED],
+                 'cpu_time'             : self.stats[PWQ_STAT_CPU_TIME],
+                 'cpu_intensive'        : self.stats[PWQ_STAT_CPU_INTENSIVE],
+                 'cm_wakeup'            : self.stats[PWQ_STAT_CM_WAKEUP],
+                 'mayday'               : self.stats[PWQ_STAT_MAYDAY],
+                 'rescued'              : self.stats[PWQ_STAT_RESCUED], }
+
+    def table_header_str():
+        return f'{"":>24} {"total":>8} {"infl":>5} {"CPUtime":>8} '\
+            f'{"CPUitsv":>7} {"CMwake":>7} {"mayday":>7} {"rescued":>7}'
+
+    def table_row_str(self):
+        cpu_intensive = '-'
+        cm_wakeup = '-'
+        mayday = '-'
+        rescued = '-'
+
+        if not self.unbound:
+            cpu_intensive = str(self.stats[PWQ_STAT_CPU_INTENSIVE])
+            cm_wakeup = str(self.stats[PWQ_STAT_CM_WAKEUP])
+
+        if self.mem_reclaim:
+            mayday = str(self.stats[PWQ_STAT_MAYDAY])
+            rescued = str(self.stats[PWQ_STAT_RESCUED])
+
+        out = f'{self.name[-24:]:24} ' \
+              f'{self.stats[PWQ_STAT_STARTED]:8} ' \
+              f'{max(self.stats[PWQ_STAT_STARTED] - self.stats[PWQ_STAT_COMPLETED], 0):5} ' \
+              f'{self.stats[PWQ_STAT_CPU_TIME] / 1000000:8.1f} ' \
+              f'{cpu_intensive:>7} ' \
+              f'{cm_wakeup:>7} ' \
+              f'{mayday:>7} ' \
+              f'{rescued:>7} '
+        return out.rstrip(':')
+
+exit_req = False
+
+def sigint_handler(signr, frame):
+    global exit_req
+    exit_req = True
+
+def main():
+    # handle args
+    table_fmt = not args.json
+    interval = args.interval
+
+    re_str = None
+    if args.workqueue:
+        for r in args.workqueue:
+            if re_str is None:
+                re_str = r
+            else:
+                re_str += '|' + r
+
+    filter_re = re.compile(re_str) if re_str else None
+
+    # monitoring loop
+    signal.signal(signal.SIGINT, sigint_handler)
+
+    while not exit_req:
+        now = time.time()
+
+        if table_fmt:
+            print()
+            print(WqStats.table_header_str())
+
+        for wq in list_for_each_entry('struct workqueue_struct', workqueues.address_of_(), 'list'):
+            stats = WqStats(wq)
+            if filter_re and not filter_re.search(stats.name):
+                continue
+            if table_fmt:
+                print(stats.table_row_str())
+            else:
+                print(stats.dict(now))
+
+        if interval == 0:
+            break
+        time.sleep(interval)
+
+if __name__ == "__main__":
+    main()