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From: Finn Thain <fthain@telegraphics.com.au>
To: "Ahmed S. Darwish" <a.darwish@linutronix.de>
Cc: Michael Schmitz <schmitzmic@gmail.com>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	"James E.J. Bottomley" <jejb@linux.ibm.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	"Sebastian A. Siewior" <bigeasy@linutronix.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] scsi: NCR5380: Remove context check
Date: Tue, 8 Dec 2020 11:12:28 +1100 (AEDT)
Message-ID: <alpine.LNX.2.23.453.2012081104380.27@nippy.intranet> (raw)
In-Reply-To: <20201206075157.19067-1-a.darwish@linutronix.de>

On Sun, 6 Dec 2020, Ahmed S. Darwish wrote:

> NCR5380_poll_politely2() uses in_interrupt() and irqs_disabled() to
> check if it is safe to sleep.
> 
> Such usage in drivers is phased out and Linus clearly requested that
> code which changes behaviour depending on context should either be
> separated, or the context be explicitly conveyed in an argument passed
> by the caller.
> 
> Below is a context analysis of NCR5380_poll_politely2() uppermost
> callers:
> 
>   - NCR5380_maybe_reset_bus(), task, invoked during device probe.
>     -> NCR5380_poll_politely()
>     -> do_abort()
> 
>   - NCR5380_select(), task, but can only sleep in the "release, then
>     re-acquire" regions of the spinlock held by its caller.
>     Sleeping invocations (lock released):
>     -> NCR5380_poll_politely2()
> 
>     Atomic invocations (lock acquired):
>     -> NCR5380_reselect()
>        -> NCR5380_poll_politely()
>        -> do_abort()
>        -> NCR5380_transfer_pio()
> 
>   - NCR5380_intr(), interrupt handler
>     -> NCR5380_dma_complete()
>        -> NCR5380_transfer_pio()
> 	  -> NCR5380_poll_politely()
>     -> NCR5380_reselect() (see above)
> 
>   - NCR5380_information_transfer(), task, but can only sleep in the
>     "release, then re-acquire" regions of the caller-held spinlock.
>     Sleeping invocations (lock released):
>       - NCR5380_transfer_pio() -> NCR5380_poll_politely()
>       - NCR5380_poll_politely()
> 
>     Atomic invocations (lock acquired):
>       - NCR5380_transfer_dma()
> 	-> NCR5380_dma_recv_setup()
>            => generic_NCR5380_precv() -> NCR5380_poll_politely()
> 	   => macscsi_pread() -> NCR5380_poll_politely()
> 
> 	-> NCR5380_dma_send_setup()
>  	   => generic_NCR5380_psend -> NCR5380_poll_politely2()
> 	   => macscsi_pwrite() -> NCR5380_poll_politely()
> 
> 	-> NCR5380_poll_politely2()
>         -> NCR5380_dma_complete()
>            -> NCR5380_transfer_pio()
> 	      -> NCR5380_poll_politely()
>       - NCR5380_transfer_pio() -> NCR5380_poll_politely
> 
>   - NCR5380_reselect(), atomic, always called with hostdata spinlock
>     held.
> 
> Since NCR5380_poll_politely2() already takes a "wait" argument in
> jiffies, use it to determine if the function can sleep. Modify atomic
> callers, which passed an unused wait value in terms of HZ, to pass zero.
> 
> Suggested-by: Finn Thain <fthain@telegraphics.com.au>
> Co-developed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
> Cc: Michael Schmitz <schmitzmic@gmail.com>
> Cc: <linux-m68k@lists.linux-m68k.org>

Acked-by: Finn Thain <fthain@telegraphics.com.au>

  reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-01  6:46 [PATCH] scsi/NCR5380: Remove in_interrupt() test Finn Thain
2020-12-01 17:05 ` Sebastian Andrzej Siewior
2020-12-03 23:08   ` Finn Thain
2020-12-04  8:38     ` Geert Uytterhoeven
2020-12-04 16:08     ` Ahmed S. Darwish
2020-12-01 18:01 ` Michael Schmitz
2020-12-04 15:32 ` [PATCH v2] scsi: NCR5380: Remove context check Ahmed S. Darwish
2020-12-05  4:28   ` Finn Thain
2020-12-06  7:51     ` [PATCH v3] " Ahmed S. Darwish
2020-12-08  0:12       ` Finn Thain [this message]
2020-12-08  1:26       ` Martin K. Petersen
2020-12-09 17:23       ` Martin K. Petersen

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