Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Wed, 10 Feb 2021 15:16:03 +1100 (AEDT)
From:   Finn Thain <fthain@telegraphics.com.au>
To:     "Song Bao Hua (Barry Song)" <song.bao.hua@hisilicon.com>
cc:     tanxiaofei <tanxiaofei@huawei.com>,
        "jejb@linux.ibm.com" <jejb@linux.ibm.com>,
        "martin.petersen@oracle.com" <martin.petersen@oracle.com>,
        "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linuxarm@openeuler.org" <linuxarm@openeuler.org>,
        "linux-m68k@vger.kernel.org" <linux-m68k@vger.kernel.org>
Subject: RE: [Linuxarm]  Re: [PATCH for-next 00/32] spin lock usage optimization
 for SCSI drivers
In-Reply-To: <88d26bd86c314e5483ec596952054be7@hisilicon.com>
Message-ID: <da111631-83ef-1ad8-799a-5d976d5759d@telegraphics.com.au>
References: <1612697823-8073-1-git-send-email-tanxiaofei@huawei.com> <31cd807d-3d0-ed64-60d-fde32cb3833c@telegraphics.com.au> <e949a474a9284ac6951813bfc8b34945@hisilicon.com> <f0a3339d-b1db-6571-fa2f-6765e150eb9d@telegraphics.com.au> 
 <88d26bd86c314e5483ec596952054be7@hisilicon.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Precedence: bulk

On Tue, 9 Feb 2021, Song Bao Hua (Barry Song) wrote:

> > > sonic_interrupt() uses an irq lock within an interrupt handler to 
> > > avoid issues relating to this. This kind of locking may be needed in 
> > > the drivers you are trying to patch. Or it might not. Apparently, 
> > > no-one has looked.
> 
> Is the comment in sonic_interrupt() outdated according to this:
> m68k: irq: Remove IRQF_DISABLED
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=77a4279
> http://lkml.iu.edu/hypermail/linux/kernel/1109.2/01687.html
> 

The removal of IRQF_DISABLED isn't relevant to this driver. Commit 
77a42796786c ("m68k: Remove deprecated IRQF_DISABLED") did not disable 
interrupts, it just removed some code to enable them.

The code and comments in sonic_interrupt() are correct. You can confirm 
this for yourself quite easily using QEMU and a cross-compiler.

> and this:
> genirq: Warn when handler enables interrupts
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b738a50a
> 
> wouldn't genirq report a warning on m68k?
> 

There is no warning from m68k builds. That's because arch_irqs_disabled() 
returns true when the IPL is non-zero.

> > 
> > Thanks
> > Barry
> 
> Thanks
> Barry
> 
>