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Subject: Re: [PATCH] scsi: ufs: add missing host_lock in setup_xfer_req
To:     Bean Huo <huobean@gmail.com>, Jaegeuk Kim <jaegeuk@kernel.org>,
        linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org
Cc:     Stanley Chu <stanley.chu@mediatek.com>,
        Can Guo <cang@codeaurora.org>, Bean Huo <beanhuo@micron.com>,
        Asutosh Das <asutoshd@codeaurora.org>
References: <20210701005117.3846179-1-jaegeuk@kernel.org>
 <38432018-e8bf-f9f3-00bf-cd4b81c95c88@acm.org>
 <69b367bc44084f901d0d71fb8f9633ea7e5df36b.camel@gmail.com>
From:   Bart Van Assche <bvanassche@acm.org>
Message-ID: <b0cd26d0-6ebc-b633-8669-a558597cc91d@acm.org>
Date:   Wed, 14 Jul 2021 11:09:20 -0700
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On 7/13/21 12:45 PM, Bean Huo wrote:
> This change only impacts on the Samsung exynos platform. and Can's
> optimization patch is to optimise the host_lock,, and removed
> host_lock, now add back in this function makes sense to me.
> but I am thinking how about hba->host_sem?

Hi Bean,

Calls of exynos_ufs_specify_nexus_t_xfer_req() must be serialized, hence 
Jaegeuks' patch. This function is called from the I/O submission path so 
performance matters. My understanding is that spinlocks have less 
overhead than semaphores. Hence the choice for a spinlock.

Thanks,

Bart.