linux-kernel - Re: [PATCH 1/2] drivers: base: power: main: Use built-in RCU list checking

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Date:   Sun, 1 Mar 2020 17:18:36 -0500
From:   Joel Fernandes <joel@...lfernandes.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Amol Grover <frextrite@...il.com>,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        "Paul E. McKenney" <paulmck@...nel.org>
Subject: Re: [PATCH 1/2] drivers: base: power: main: Use built-in RCU list checking

On Sun, Mar 1, 2020 at 4:23 PM Rafael J. Wysocki <rafael@...nel.org> wrote:
>
> On Sun, Mar 1, 2020 at 9:53 PM <joel@...lfernandes.org> wrote:
> >
> >
> >
> > On March 1, 2020 3:12:53 PM EST, "Rafael J. Wysocki" <rafael@...nel.org> wrote:
> > >On Fri, Feb 28, 2020 at 6:47 PM <madhuparnabhowmik10@...il.com> wrote:
> > >>
> > >> From: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
> > >>
> > >> This patch passes the cond argument to list_for_each_entry_rcu()
> > >> to fix the following false-positive lockdep warnings:
> > >>
> > >> [  330.302784] =============================
> > >> [  330.302789] WARNING: suspicious RCU usage
> > >> [  330.302796] 5.6.0-rc1+ #5 Not tainted
> > >> [  330.302801] -----------------------------
> > >> [  330.302808] drivers/base/power/main.c:326 RCU-list traversed in
> > >non-reader section!!
> > >>
> > >> [  330.303303] =============================
> > >> [  330.303307] WARNING: suspicious RCU usage
> > >> [  330.303311] 5.6.0-rc1+ #5 Not tainted
> > >> [  330.303315] -----------------------------
> > >> [  330.303319] drivers/base/power/main.c:1698 RCU-list traversed in
> > >non-reader section!!
> > >>
> > >> [  331.934969] =============================
> > >> [  331.934971] WARNING: suspicious RCU usage
> > >> [  331.934973] 5.6.0-rc1+ #5 Not tainted
> > >> [  331.934975] -----------------------------
> > >> [  331.934977] drivers/base/power/main.c:1238 RCU-list traversed in
> > >non-reader section!!
> > >>
> > >> [  332.467772] WARNING: suspicious RCU usage
> > >> [  332.467775] 5.6.0-rc1+ #5 Not tainted
> > >> [  332.467775] -----------------------------
> > >> [  332.467778] drivers/base/power/main.c:269 RCU-list traversed in
> > >non-reader section!!
> > >
> > >I don't see these warnings in the kernels run locally here.
> > >
> > >What do you do to get them?
> > >
> > >Joel, any comments here?
> >
> > You have to enable lockdep in your config. Does your setup have that?
>
> CONFIG_LOCK_DEBUGGING_SUPPORT=y
> CONFIG_PROVE_LOCKING=y
> CONFIG_DEBUG_SPINLOCK=y
> CONFIG_DEBUG_LOCK_ALLOC=y
> CONFIG_LOCKDEP=y

This should be it. I am not sure what else Madhuparna did to trigger
it. Madhuparna, could you elaborate?

thanks,

 - Joel