linux-kernel - Re: [PATCH] iommu/vt-d: silence a RCU-list debugging warning

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Date:   Thu, 19 Mar 2020 15:16:19 +0100
From:   Joerg Roedel <jroedel@...e.de>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     Qian Cai <cai@....pw>, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommu/vt-d: silence a RCU-list debugging warning

On Wed, Mar 18, 2020 at 01:27:53PM +0800, Lu Baolu wrote:
> On 2020/3/17 23:03, Qian Cai wrote:
> > dmar_find_atsr() calls list_for_each_entry_rcu() outside of an RCU read
> > side critical section but with dmar_global_lock held. Silence this
> > false positive.
> > 
> >   drivers/iommu/intel-iommu.c:4504 RCU-list traversed in non-reader section!!
> >   1 lock held by swapper/0/1:
> >   #0: ffffffff9755bee8 (dmar_global_lock){+.+.}, at: intel_iommu_init+0x1a6/0xe19
> > 
> >   Call Trace:
> >    dump_stack+0xa4/0xfe
> >    lockdep_rcu_suspicious+0xeb/0xf5
> >    dmar_find_atsr+0x1ab/0x1c0
> >    dmar_parse_one_atsr+0x64/0x220
> >    dmar_walk_remapping_entries+0x130/0x380
> >    dmar_table_init+0x166/0x243
> >    intel_iommu_init+0x1ab/0xe19
> >    pci_iommu_init+0x1a/0x44
> >    do_one_initcall+0xae/0x4d0
> >    kernel_init_freeable+0x412/0x4c5
> >    kernel_init+0x19/0x193
> > 
> > Signed-off-by: Qian Cai <cai@....pw>
> 
> How about changing the commit subject to
> "iommu/vt-d: Silence RCU-list debugging warning in dmar_find_atsr()"?
> 
> Acked-by: Lu Baolu <baolu.lu@...ux.intel.com>

Fixed up the subject and applied it, thanks.