From mboxrd@z Thu Jan  1 00:00:00 1970
From: Doug Ledford <dledford@redhat.com>
Subject: Re: [PATCH V2] IB/hfi1,IB/qib: Fix qp_stats sleep with rcu read lock
 held
Date: Mon, 22 Aug 2016 14:32:23 -0400
Message-ID: <c67f0026-691c-b13a-eae7-109a5ebc4016@redhat.com>
References: <1471015057-9886-1-git-send-email-ira.weiny@intel.com>
 <20160814085511.GB21270@leon.nu>
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To: Leon Romanovsky <leon@kernel.org>, ira.weiny@intel.com
Cc: linux-rdma@vger.kernel.org, Mike Marciniszyn <mike.marciniszyn@intel.com>, stable@vger.kernel.org
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From: Doug Ledford <dledford@redhat.com>
To: Leon Romanovsky <leon@kernel.org>, ira.weiny@intel.com
Cc: linux-rdma@vger.kernel.org, Mike Marciniszyn
 <mike.marciniszyn@intel.com>, stable@vger.kernel.org
Message-ID: <c67f0026-691c-b13a-eae7-109a5ebc4016@redhat.com>
Subject: Re: [PATCH V2] IB/hfi1,IB/qib: Fix qp_stats sleep with rcu read lock
 held
References: <1471015057-9886-1-git-send-email-ira.weiny@intel.com>
 <20160814085511.GB21270@leon.nu>
In-Reply-To: <20160814085511.GB21270@leon.nu>

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On 8/14/2016 4:55 AM, Leon Romanovsky wrote:
> On Fri, Aug 12, 2016 at 11:17:37AM -0400, ira.weiny@intel.com wrote:
>> From: Mike Marciniszyn <mike.marciniszyn@intel.com>
>>
>> The qp init function does a kzalloc() while holding the RCU
>> lock that encounters the following warning with a debug kernel
>> when a cat of the qp_stats is done:
>>
>> [  231.723948] rcu_scheduler_active =3D 1, debug_locks =3D 0
>> [  231.731939] 3 locks held by cat/11355:
>> [  231.736492]  #0:  (debugfs_srcu){......}, at: [<ffffffff813001a5>] =
debugfs_use_file_start+0x5/0x90
>> [  231.746955]  #1:  (&p->lock){+.+.+.}, at: [<ffffffff81289a6c>] seq_=
read+0x4c/0x3c0
>> [  231.755873]  #2:  (rcu_read_lock){......}, at: [<ffffffffa0a0c535>]=
 _qp_stats_seq_start+0x5/0xd0 [hfi1]
>> [  231.766862]
>>
>> The init functions do an implicit next which requires the rcu read loc=
k
>> before the kzalloc().
>>
>> Fix for both drivers is to change the scope of the init function to on=
ly
>> do the allocation and the initialization of the just allocated iter.
>>
>> The implict next is moved back into the respective start functions to =
fix
>> the issue.
>>
>> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
>> Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
>> CC: <stable@vger.kernel.org> # 4.6.x-
>>
>> ---
>> Changes from V1:
>> 	use do.. while loop to execute first iter call.
>=20
> Thanks,
> Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
>=20

Sorry, responded to v1 email, but I applied the v2 patch.

--=20
Doug Ledford <dledford@redhat.com>
    GPG Key ID: 0E572FDD


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