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

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Date:   Mon, 2 Mar 2020 18:02:21 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
Cc:     Joel Fernandes <joel@...lfernandes.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        "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 Mon, Mar 2, 2020 at 1:34 PM Madhuparna Bhowmik
<madhuparnabhowmik10@...il.com> wrote:
>
>
>
> On Mon, 2 Mar, 2020, 3:48 AM Joel Fernandes, <joel@...lfernandes.org> wrote:
>>
>> 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
>>
>>
> I had CONFIG_PROVE_RCU_LIST = y and I think these warnings were triggered when I had closed my laptop (like just close without shutting down).

OK, so let's define a macro for that in this file to avoid code duplication.

And analogously in the second patch.

Thanks!