linux-kernel - Re: [PATCH RESEND] iommu: dmar: Fix RCU list debugging warnings

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Date:   Mon, 2 Mar 2020 17:04:13 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     Amol Grover <frextrite@...il.com>
Cc:     Allison Randal <allison@...utok.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>, Qian Cai <cai@....pw>,
        Deepa Dinamani <deepa.kernel@...il.com>,
        linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        Joel Fernandes <joel@...lfernandes.org>,
        Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>,
        "Paul E . McKenney" <paulmck@...nel.org>
Subject: Re: [PATCH RESEND] iommu: dmar: Fix RCU list debugging warnings

On Sun, Feb 23, 2020 at 10:25:39PM +0530, Amol Grover wrote:
> dmar_drhd_units is traversed using list_for_each_entry_rcu()
> outside of an RCU read side critical section but under the
> protection of dmar_global_lock. Hence add corresponding lockdep
> expression to silence the following false-positive warnings:
> 
> [    1.603975] =============================
> [    1.603976] WARNING: suspicious RCU usage
> [    1.603977] 5.5.4-stable #17 Not tainted
> [    1.603978] -----------------------------
> [    1.603980] drivers/iommu/intel-iommu.c:4769 RCU-list traversed in non-reader section!!
> 
> [    1.603869] =============================
> [    1.603870] WARNING: suspicious RCU usage
> [    1.603872] 5.5.4-stable #17 Not tainted
> [    1.603874] -----------------------------
> [    1.603875] drivers/iommu/dmar.c:293 RCU-list traversed in non-reader section!!
> 
> Tested-by: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
> Signed-off-by: Amol Grover <frextrite@...il.com>
> ---
>  include/linux/dmar.h | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)

Applied, thanks.