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From:   Justin Tee <justin.tee@broadcom.com>
Date:   Thu, 27 Jul 2023 10:53:21 -0700
Message-ID: <CAAmqgVM6HDtWAex4WkNqWRKQRag3EAHPPgk5HC1wzFg4Ae6gkQ@mail.gmail.com>
Subject: Re: [PATCH] scsi: lpfc: Fix potential deadlock on &phba->hbalock
To:     Chengfeng Ye <dg573847474@gmail.com>
Cc:     james.smart@broadcom.com, dick.kennedy@broadcom.com,
        jejb@linux.ibm.com, martin.petersen@oracle.com,
        linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org
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Hi Chengfeng,

That=E2=80=99s still a unlikely scenario:

        /* Check device state for handling interrupt */
        if (unlikely(lpfc_intr_state_check(phba))) {
                /* Check again for link_state with lock held */
                spin_lock_irqsave(&phba->hbalock, iflag);
                if (phba->link_state < LPFC_LINK_DOWN)
                        /* Flush, clear interrupt, and rearm the EQ */
                        lpfc_sli4_eqcq_flush(phba, fpeq);
                spin_unlock_irqrestore(&phba->hbalock, iflag);
                return IRQ_NONE;
        }

In order to enter that if statement and obtain the hbalock, the PCI
channel has to be offline or the HBA=E2=80=99s link is in not in an
initialized state.  If either of those were true, lpfc_cmpl_els_uvem
would never get called to begin with.

Thanks,
Justin


On Wed, Jul 26, 2023 at 10:40=E2=80=AFPM Chengfeng Ye <dg573847474@gmail.co=
m> wrote:
>
> Hi Justin,
>
> Thanks much for the reply,  it is my negligence of not have noticed it,
> and sorry for this.
>
> I inspect the bug report of my tool again and just find that actually
> lpfc_sli4_intr_handler() also acquires that lock.
>
> lpfc_sli4_intr_handler()
>     -> lpfc_sli4_hba_intr_handler()
>     -> spin_lock_irqsave(&phba->hbalock, iflag);
>
> It seems like this isr is called on an SLI4 type HBA. If consider this
> one could it be a deadlock problem?
>
> Thanks again,
> Chengfeng

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