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[95.91.236.101]) by smtp.googlemail.com with ESMTPSA id v2sm3825333wro.48.2021.07.14.14.22.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 Jul 2021 14:22:25 -0700 (PDT) Message-ID: <5f6b14c0a86e419b05102599602307a4782d8c64.camel@gmail.com> Subject: Re: [PATCH] scsi: ufs: add missing host_lock in setup_xfer_req From: Bean Huo To: Bart Van Assche , Jaegeuk Kim , linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org Cc: Stanley Chu , Can Guo , Bean Huo , Asutosh Das Date: Wed, 14 Jul 2021 23:22:24 +0200 In-Reply-To: References: <20210701005117.3846179-1-jaegeuk@kernel.org> <38432018-e8bf-f9f3-00bf-cd4b81c95c88@acm.org> <69b367bc44084f901d0d71fb8f9633ea7e5df36b.camel@gmail.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.36.5-0ubuntu1 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.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