linux-kernel - Re: [BUG] scsi: lpfc: possible ABBA deadlock

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Message-ID: <5496b03b-49aa-88e3-e058-1d97c91b1b0b@gmail.com>
Date:   Sat, 24 Jul 2021 13:18:27 -0700
From:   James Smart <jsmart2021@...il.com>
To:     Jia-Ju Bai <baijiaju1990@...il.com>, james.smart@...adcom.com,
        dick.kennedy@...adcom.com, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] scsi: lpfc: possible ABBA deadlock

On 7/15/2021 3:37 AM, Jia-Ju Bai wrote:
> Hello,
> 
> I find there is a possible ABBA deadlock in the lpfc driver in Linux 5.10:
> 
> In lpfc_nvmet_unsol_fcp_issue_abort():
> 3502:     spin_lock_irqsave(&ctxp->ctxlock, flags);
> 3504: spin_lock(&phba->sli4_hba.abts_nvmet_buf_list_lock);
> 
> In lpfc_sli4_nvmet_xri_aborted():
> 1787: spin_lock(&phba->sli4_hba.abts_nvmet_buf_list_lock);
> 1794:     spin_lock(&ctxp->ctxlock);
> 
> When lpfc_nvmet_unsol_fcp_issue_abort() and 
> lpfc_sli4_nvmet_xri_aborted() are concurrently executed, the deadlock 
> can occur.
> 
> I am not quite sure whether this possible deadlock is real and how to 
> fix it if it is real.
> Any feedback would be appreciated, thanks :)
> 
> 
> Best wishes,
> Jia-Ju Bai

Jia-Ju,

It's a valid issue, but rather difficult to actually occur. We've put 
together a fix and am testing it. Will post when ready.

-- james