linux-kernel - Re: WARNING: suspicious RCU usage in modeset

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Message-ID: <c0ed329a-1349-5d07-5b60-0a89d9fb9de3@i-love.sakura.ne.jp>
Date:   Sat, 19 Dec 2020 10:00:02 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     "Paul E. McKenney" <paulmck@...nel.org>
Cc:     Daniel Vetter <daniel.vetter@...ll.ch>,
        syzbot <syzbot+972b924c988834e868b2@...kaller.appspotmail.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Josh Triplett <josh@...htriplett.org>, rcu@...r.kernel.org,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Nathan Chancellor <natechancellor@...il.com>,
        Peter Rosin <peda@...ntia.se>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Boqun Feng <boqun.feng@...il.com>
Subject: Re: WARNING: suspicious RCU usage in modeset_lock

On Wed, Dec 16, 2020 at 5:16 PM Paul E. McKenney <paulmck@...nel.org> wrote:
> In my experience, lockdep will indeed complain if an interrupt handler
> returns while in an RCU read-side critical section.

Can't we add lock status checks into the beginning and the end of interrupt handler functions
(e.g. whether "struct task_struct"->lockdep_depth did not change) ?