On Fri, 4 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@xxxxxxxxxxxxxxxxxxx>
> Co-developed-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> Signed-off-by: Ahmed S. Darwish <a.darwish@xxxxxxxxxxxxx>
> Cc: Michael Schmitz <schmitzmic@xxxxxxxxx>
> Cc: <linux-m68k@xxxxxxxxxxxxxxxxxxxx>
> ---
> drivers/scsi/NCR5380.c | 77 ++++++++++++++++++++++------------------
> drivers/scsi/NCR5380.h | 3 +-
> drivers/scsi/g_NCR5380.c | 12 +++----
> drivers/scsi/mac_scsi.c | 10 +++---
> 4 files changed, 55 insertions(+), 47 deletions(-)
>
> diff --git a/drivers/scsi/NCR5380.c b/drivers/scsi/NCR5380.c
> index d654a6cc4162..60200f61592e 100644
> --- a/drivers/scsi/NCR5380.c
> +++ b/drivers/scsi/NCR5380.c
> @@ -132,7 +132,7 @@
> static unsigned int disconnect_mask = ~0;
> module_param(disconnect_mask, int, 0444);
>
> -static int do_abort(struct Scsi_Host *);
> +static int do_abort(struct Scsi_Host *, unsigned int);
> static void do_reset(struct Scsi_Host *);
> static void bus_reset_cleanup(struct Scsi_Host *);
>
> @@ -197,7 +197,7 @@ static inline void set_resid_from_SCp(struct scsi_cmnd *cmd)
> * @reg2: Second 5380 register to poll
> * @bit2: Second bitmask to check
> * @val2: Second expected value
> - * @wait: Time-out in jiffies
> + * @wait: Time-out in jiffies, 0 if sleeping is not allowed
> *
> * Polls the chip in a reasonably efficient manner waiting for an
> * event to occur. After a short quick poll we begin to yield the CPU
> @@ -213,7 +213,7 @@ static int NCR5380_poll_politely2(struct NCR5380_hostdata *hostdata,
> unsigned long wait)
> {
> unsigned long n = hostdata->poll_loops;
> - unsigned long deadline = jiffies + wait;
> + unsigned long deadline;
>
> do {
> if ((NCR5380_read(reg1) & bit1) == val1)
> @@ -223,10 +223,11 @@ static int NCR5380_poll_politely2(struct NCR5380_hostdata *hostdata,
> cpu_relax();
> } while (n--);
>
> - if (irqs_disabled() || in_interrupt())
> + if (!wait)
> return -ETIMEDOUT;
>
> /* Repeatedly sleep for 1 ms until deadline */
> + deadline = jiffies + wait;
> while (time_is_after_jiffies(deadline)) {
> schedule_timeout_uninterruptible(1);
> if ((NCR5380_read(reg1) & bit1) == val1)
The deadline assignment shouldn't be moved. That's a behavioural change
and doesn't fit under the stated aim of this patch. Also, it isn't
actually a desirable change: the argument to this function is the overall
wait time, not just the sleep limit.
The rest looks ok.
