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

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Message-ID: <B76D77A74C894381BBF8365C5607758B@usish.com.cn>
Date:	Mon, 27 Feb 2012 16:29:50 +0800
From:	"Jack Wang" <jack_wang@...sh.com>
To:	"'santosh prasad nayak'" <santoshprasadnayak@...il.com>,
	"'Dan Carpenter'" <dan.carpenter@...cle.com>
Cc:	<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.

Thanks for fix.
Acked-by: Jack Wang <jack_wang@...sh.com>
> 
>  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). If intention of the developer is to enable the interrupt
during
> execution of ' mpi_sata_completion' , then the code changes in the patch
> looks ok.
> 
> If interrupt should not be enabled during execution of
> 'mpi_sata_completion' then
> we can use simple  spin_lock and spin_unlock.
> 
> 
> regards
> santosh
> 
> 
> On Sun, Feb 26, 2012 at 8:37 PM, Dan Carpenter <dan.carpenter@...cle.com>
> wrote:
> > 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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