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From: Saurav Kashyap <saurav.kashyap@qlogic.com>
To: Jiri Kosina <jkosina@suse.cz>,
        "James E.J. Bottomley" <JBottomley@parallels.com>,
        Dept-Eng Linux Driver <Linux-Driver@qlogic.com>,
        Andrew Vasquez <andrew.vasquez@qlogic.com>
CC: "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Nicholas Bellinger <nab@linux-iscsi.org>,
        "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
Date: Mon, 8 Oct 2012 11:43:42 -0500
Subject: Re: [PATCH] [RESEND] qla2xxx: fix potential deadlock on
 ha->hardware_lock
Thread-Topic: [PATCH] [RESEND] qla2xxx: fix potential deadlock on
 ha->hardware_lock
Thread-Index: Ac2ldBN8tnjqPjPzSlqXvRznbp/8yQ==
Message-ID: <CC98FFD9.ECEC%saurav.kashyap@qlogic.com>
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Acked-by: Saurav Kashyap <saurav.kashyap@qlogic.com>

Thanks,
~Saurav


>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-and-tested-by: Srivatsa S. Bhat
><srivatsa.bhat@linux.vnet.ibm.com>
>Signed-off-by: Jiri Kosina <jkosina@suse.cz>
>---
> 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,
>
>--
>Jiri Kosina
>SUSE Labs
>--
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