[Bug runtime/30831] Systemtap scripts fail to compile on newest linux 6.6 kernels

["wcohen at redhat dot com" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=30831

--- 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
issues.
 git commit c4f135d643823a869becfa87539f7820ef9d5bfa has details on the issues:


Author: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>  2022-06-01 03:32:47
Committer: Tejun Heo <tj@kernel.org>  2022-06-07 13:07:14
Parent: e71e60cd74df9386c3f684c54888f2367050b831 (Merge tag
'dma-mapping-5.19-2022-06-06' of git://git.infradead.org/users/hch/dma-mapping)
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
    inevitable.

    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
    flush_scheduled_work().

    Link: https://lore.kernel.org/all/YgnQGZWT%2Fn3VAITX@slm.duckdns.org/ [1]
    Link: https://syzkaller.appspot.com/bug?extid=bde0f89deacca7c765b8 [2]
    Link:
https://lkml.kernel.org/r/49925af7-78a8-a3dd-bce6-cfc02e1a9236@I-love.SAKURA.ne.jp
[3]
    Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
    Signed-off-by: Tejun Heo <tj@kernel.org>

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