linux-kernel - Re: [PATCH 1/2] [SCSI] pm8001: Fix bogus interrupt state flag issue.

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Date:	Sun, 26 Feb 2012 18:07:20 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	santosh nayak <santoshprasadnayak@...il.com>
Cc:	jack_wang@...sh.com, lindar_liu@...sh.com,
	JBottomley@...allels.com, linux-scsi@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 1/2] [SCSI] pm8001: Fix bogus interrupt state flag issue.

On Sun, Feb 26, 2012 at 07:03:30PM +0530, santosh nayak wrote:
> From: Santosh Nayak <santoshprasadnayak@...il.com>
> 
> Static checker is giving following warning:
> " error: calling 'spin_unlock_irqrestore()' with bogus flags"
> 
> The code flow is as shown below:
> process_oq() --> process_one_iomb --> mpi_sata_completion
> 
> In 'mpi_sata_completion'
> the first call for 'spin_unlock_irqrestore()' is with flags=0,
> which is as good as 'spin_unlock_irq()' ( unconditional interrupt
> enabling).
> 
> So for better performance 'spin_unlock_irqrestore()' can be replaced
> with 'spin_unlock_irq()' and 'spin_lock_irqsave()' can be replaced by
> 'spin_lock_irq()'.
> 

process_oq() is called from the interrupt handler pm8001_chip_isr()
with interrupts disabled.

drivers/scsi/pm8001/pm8001_hwi.c
  4301          spin_lock_irqsave(&pm8001_ha->lock, flags);
  4302          pm8001_chip_interrupt_disable(pm8001_ha);
  4303          process_oq(pm8001_ha);
  4304          pm8001_chip_interrupt_enable(pm8001_ha);
  4305          spin_unlock_irqrestore(&pm8001_ha->lock, flags);

Probably we should just be doing a spin_lock() and spin_unlock()
without re-enabling the IRQs.  Should we even be doing that in the
irq handler anyway?

regards,
dan carpenter


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