public inbox for
 help / color / mirror / Atom feed
From: "wcohen at redhat dot com" <>
Subject: [Bug runtime/30831] Systemtap scripts fail to compile on newest  linux 6.6 kernels
Date: Fri, 08 Sep 2023 02:49:18 +0000	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

--- Comment #2 from William Cohen <wcohen at redhat dot com> ---
A bit more data.  The reproducer works with Fedora Rawhide
kernel-6.5.0-57.fc40.x86_64.  The failure happens with the later 6.6 kernels.

There are two issues going on:
-problem with the type used for the ibt_wrapper for task_work_add.
-use of flush_scheduled_work() is frowned upon because of possible deadlock
 git commit c4f135d643823a869becfa87539f7820ef9d5bfa has details on the issues:

Author: Tetsuo Handa <>  2022-06-01 03:32:47
Committer: Tejun Heo <>  2022-06-07 13:07:14
Parent: e71e60cd74df9386c3f684c54888f2367050b831 (Merge tag
'dma-mapping-5.19-2022-06-06' of git://
Child:  873a400938b31a1e443c4d94b560b78300787540 (workqueue: Fix type of cpu in
trace event)
Branches: master, remotes/origin/master, remotes/origin/mmu_gather-race-fix,
remotes/origin/x86-rep-insns, remotes/origin/x86-uaccess-cleanup
Follows: v5.19-rc1
Precedes: v5.19-rc2

    workqueue: Wrap flush_workqueue() using a macro

    Since flush operation synchronously waits for completion, flushing
    system-wide WQs (e.g. system_wq) might introduce possibility of deadlock
    due to unexpected locking dependency. Tejun Heo commented at [1] that it
    makes no sense at all to call flush_workqueue() on the shared WQs as the
    caller has no idea what it's gonna end up waiting for.

    Although there is flush_scheduled_work() which flushes system_wq WQ with
    "Think twice before calling this function! It's very easy to get into
    trouble if you don't take great care." warning message, syzbot found a
    circular locking dependency caused by flushing system_wq WQ [2].

    Therefore, let's change the direction to that developers had better use
    their local WQs if flush_scheduled_work()/flush_workqueue(system_*_wq) is

    Steps for converting system-wide WQs into local WQs are explained at [3],
    and a conversion to stop flushing system-wide WQs is in progress. Now we
    want some mechanism for preventing developers who are not aware of this
    conversion from again start flushing system-wide WQs.

    Since I found that WARN_ON() is complete but awkward approach for teaching
    developers about this problem, let's use __compiletime_warning() for
    incomplete but handy approach. For completeness, we will also insert
    WARN_ON() into __flush_workqueue() after all in-tree users stopped calling

    Link: [1]
    Link: [2]
    Signed-off-by: Tetsuo Handa <>
    Signed-off-by: Tejun Heo <>

You are receiving this mail because:
You are the assignee for the bug.

  parent reply	other threads:[~2023-09-08  2:49 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-09-07 17:46 [Bug runtime/30831] New: The do_each_thread macro has been removed from " wcohen at redhat dot com
2023-09-07 19:23 ` [Bug runtime/30831] Systemtap scripts fail to compile on " wcohen at redhat dot com
2023-09-08  2:49 ` wcohen at redhat dot com [this message]
2023-09-18 13:46 ` wcohen at redhat dot com
2023-09-18 13:51 ` wcohen at redhat dot com
2023-09-27 14:24 ` wcohen at redhat dot com
2023-09-27 20:03 ` wcohen at redhat dot com
2023-11-23 15:16   ` Tetsuo Handa
2023-12-13 14:47     ` William Cohen
2023-12-17 10:41       ` Tetsuo Handa

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).