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Date: Thu, 04 Oct 2012 21:11:53 +0530
From: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
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To: Jiri Kosina <jkosina@suse.cz>
CC: linux-scsi@vger.kernel.org, James.Bottomley@hansenpartnership.com,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Nicholas Bellinger <nab@linux-iscsi.org>
Subject: Re: [qla2xxx] INFO: possible irq lock inversion dependency detected
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Hi Jiri,

Thanks for taking a look!
 
> This seems to be real. You should be seeing that since 3.5-rc1 already 
> though ... ?
> 
> Does the patch below fix that?
> 

Yes, it does, thanks! But 3.6-rc kernels were booting fine as far as I remember.
I'll check again and get back tomorrow.

> 
> From: Jiri Kosina <jkosina@suse.cz>
> Subject: [PATCH] [SCSI] qla2xxx: fix potential deadlock on ha->hardware_lock
> 
> Lockdep reports:
> 
> === [ cut here ] ===
>  =========================================================
>  [ INFO: possible irq lock inversion dependency detected ]
>  3.6.0-0.0.0.28.36b5ec9-default #1 Not tainted
>  ---------------------------------------------------------
>  qla2xxx_1_dpc/368 just changed the state of lock:
>   (&(&ha->vport_slock)->rlock){+.....}, at: [<ffffffffa009b377>] qla2x00_configure_hba+0x197/0x3c0 [qla2xxx]
>  but this lock was taken by another, HARDIRQ-safe lock in the past:
>   (&(&ha->hardware_lock)->rlock){-.....}
> 
> and interrupts could create inverse lock ordering between them.
> 
> other info that might help us debug this:
>  Possible interrupt unsafe locking scenario:
> 
>        CPU0                    CPU1
>        ----                    ----
>   lock(&(&ha->vport_slock)->rlock);
>                                local_irq_disable();
>                                lock(&(&ha->hardware_lock)->rlock);
>                                lock(&(&ha->vport_slock)->rlock);
>   <Interrupt>
>     lock(&(&ha->hardware_lock)->rlock);
> === [ cut here ] ===
> 
> Fix the potential deadlock by disabling IRQs while holding ha->vport_slock.
> 
> Reported-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
> Signed-off-by: Jiri Kosina <jkosina@suse.cz>

Tested-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>

Regards,
Srivatsa S. Bhat

> ---
>  drivers/scsi/qla2xxx/qla_init.c |    5 +++--
>  1 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/scsi/qla2xxx/qla_init.c b/drivers/scsi/qla2xxx/qla_init.c
> index 799a58b..48fca47 100644
> --- a/drivers/scsi/qla2xxx/qla_init.c
> +++ b/drivers/scsi/qla2xxx/qla_init.c
> @@ -2080,6 +2080,7 @@ qla2x00_configure_hba(scsi_qla_host_t *vha)
>  	uint8_t       domain;
>  	char		connect_type[22];
>  	struct qla_hw_data *ha = vha->hw;
> +	unsigned long flags;
> 
>  	/* Get host addresses. */
>  	rval = qla2x00_get_adapter_id(vha,
> @@ -2154,9 +2155,9 @@ qla2x00_configure_hba(scsi_qla_host_t *vha)
>  	vha->d_id.b.area = area;
>  	vha->d_id.b.al_pa = al_pa;
> 
> -	spin_lock(&ha->vport_slock);
> +	spin_lock_irqsave(&ha->vport_slock, flags);
>  	qlt_update_vp_map(vha, SET_AL_PA);
> -	spin_unlock(&ha->vport_slock);
> +	spin_unlock_irqrestore(&ha->vport_slock, flags);
> 
>  	if (!vha->flags.init_done)
>  		ql_log(ql_log_info, vha, 0x2010,
> 

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