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From: Bean Huo <huobean@gmail.com>
To: Bart Van Assche <bvanassche@acm.org>,
	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>
Subject: Re: [PATCH] scsi: ufs: add missing host_lock in setup_xfer_req
Date: Wed, 14 Jul 2021 23:22:24 +0200	[thread overview]
Message-ID: <5f6b14c0a86e419b05102599602307a4782d8c64.camel@gmail.com> (raw)
In-Reply-To: <b0cd26d0-6ebc-b633-8669-a558597cc91d@acm.org>

On Wed, 2021-07-14 at 11:09 -0700, Bart Van Assche wrote:
> 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,

After adding spin_lock/unlock_irqsave()
in ufshcd_vops_setup_xfer_req(), there will be 4 times of call of
host_lock lock/unlock in ufshcd_send_command(). Reduce the code scope
of protection, but increase the number of calls to
spin_lock/unlock_irqsave().  Almost each sub-funciton
in ufshcd_send_command() calls spin_lock/unlock_irqsave(). why not
directly take spin_lock/unlock_irqsave() away from each sub-fun, and
increase the scope in ufshcd_send_command()?

Bean







> Bart


      reply	other threads:[~2021-07-14 21:22 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-01  0:51 [PATCH] scsi: ufs: add missing host_lock in setup_xfer_req Jaegeuk Kim
2021-07-01 15:23 ` Bart Van Assche
2021-07-01 17:00   ` Bart Van Assche
2021-07-13 19:06 ` Bart Van Assche
2021-07-13 19:45   ` Bean Huo
2021-07-14 18:09     ` Bart Van Assche
2021-07-14 21:22       ` Bean Huo [this message]

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