linux-kernel - RE: [Linuxarm] Re: [PATCH for-next 00/32] spin lock usage optimization for SCSI drivers

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Date:   Tue, 9 Feb 2021 01:48:15 +0000
From:   "Song Bao Hua (Barry Song)" <song.bao.hua@...ilicon.com>
To:     Finn Thain <fthain@...egraphics.com.au>,
        tanxiaofei <tanxiaofei@...wei.com>
CC:     "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linuxarm@...neuler.org" <linuxarm@...neuler.org>
Subject: RE: [Linuxarm]  Re: [PATCH for-next 00/32] spin lock usage
 optimization for SCSI drivers



> -----Original Message-----
> From: Finn Thain [mailto:fthain@...egraphics.com.au]
> Sent: Monday, February 8, 2021 8:57 PM
> To: tanxiaofei <tanxiaofei@...wei.com>
> Cc: jejb@...ux.ibm.com; martin.petersen@...cle.com;
> linux-scsi@...r.kernel.org; linux-kernel@...r.kernel.org;
> linuxarm@...neuler.org
> Subject: [Linuxarm] Re: [PATCH for-next 00/32] spin lock usage optimization
> for SCSI drivers
> 
> On Sun, 7 Feb 2021, Xiaofei Tan wrote:
> 
> > Replace spin_lock_irqsave with spin_lock in hard IRQ of SCSI drivers.
> > There are no function changes, but may speed up if interrupt happen too
> > often.
> 
> This change doesn't necessarily work on platforms that support nested
> interrupts.
> 
> Were you able to measure any benefit from this change on some other
> platform?

I think the code disabling irq in hardIRQ is simply wrong.
Since this commit
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e58aa3d2d0cc
genirq: Run irq handlers with interrupts disabled

interrupt handlers are definitely running in a irq-disabled context
unless irq handlers enable them explicitly in the handler to permit
other interrupts.

> 
> Please see also,
> https://lore.kernel.org/linux-scsi/89c5cb05cb844939ae684db0077f675f@h3c.co
> m/
> _______________________________________________
> Linuxarm mailing list -- linuxarm@...neuler.org
> To unsubscribe 

Thanks
Barry