linux-kernel - Re: [RESEND PATCH] scsi: ufs: fix race between clock gating and devfreq scaling work

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Date:   Fri, 14 Oct 2016 16:47:39 -0400
From:   "Martin K. Petersen" <martin.petersen@...cle.com>
To:     Subhash Jadavani <subhashj@...eaurora.org>
Cc:     vinholikatti@...il.com, jejb@...ux.vnet.ibm.com,
        martin.petersen@...cle.com,
        linux-scsi@...r.kernel.org (open list:UNIVERSAL FLASH STORAGE HOST
        CONTROLLER DRIVER), linux-kernel@...r.kernel.org (open list)
Subject: Re: [RESEND PATCH] scsi: ufs: fix race between clock gating and devfreq scaling work

>>>>> "Subhash" == Subhash Jadavani <subhashj@...eaurora.org> writes:

Subhash> UFS devfreq clock scaling work may require clocks to be ON if
Subhash> it need to execute some UFS commands hence it may request for
Subhash> clock hold before issuing the command. But if UFS clock gating
Subhash> work is already running in parallel, ungate work would end up
Subhash> waiting for the clock gating work to finish and as clock gating
Subhash> work would also wait for the clock scaling work to finish, we
Subhash> would enter in deadlock state. Here is the call trace during
Subhash> this deadlock state:

Somebody from the UFS camp, please review!

-- 
Martin K. Petersen	Oracle Linux Engineering