> -----Original Message-----
> From: Finn Thain [mailto:[email protected]]
> Sent: Friday, February 12, 2021 12:57 PM
> To: Song Bao Hua (Barry Song) <[email protected]>
> Cc: tanxiaofei <[email protected]>; [email protected];
> [email protected]; [email protected];
> [email protected]; [email protected];
> [email protected]
> Subject: RE: Re: [PATCH for-next 00/32] spin lock usage optimization for SCSI
> drivers
>
>
> On Thu, 11 Feb 2021, Song Bao Hua (Barry Song) wrote:
>
> >
> > Actually in m68k, I also saw its IRQ entry disabled interrupts by
> > ' move #0x2700,%sr /* disable intrs */'
> >
> > arch/m68k/include/asm/entry.h:
> >
> > .macro SAVE_ALL_SYS
> > move #0x2700,%sr /* disable intrs */
> > btst #5,%sp@(2) /* from user? */
> > bnes 6f /* no, skip */
> > movel %sp,sw_usp /* save user sp */
> > ...
> >
> > .macro SAVE_ALL_INT
> > SAVE_ALL_SYS
> > moveq #-1,%d0 /* not system call entry */
> > movel %d0,%sp@(PT_OFF_ORIG_D0)
> > .endm
> >
> > arch/m68k/kernel/entry.S:
> >
> > /* This is the main interrupt handler for autovector interrupts */
> >
> > ENTRY(auto_inthandler)
> > SAVE_ALL_INT
> > GET_CURRENT(%d0)
> > | put exception # in d0
> > bfextu %sp@(PT_OFF_FORMATVEC){#4,#10},%d0
> > subw #VEC_SPUR,%d0
> >
> > movel %sp,%sp@-
> > movel %d0,%sp@- | put vector # on stack
> > auto_irqhandler_fixup = . + 2
> > jsr do_IRQ | process the IRQ
> > addql #8,%sp | pop parameters off stack
> > jra ret_from_exception
> >
> > So my question is that " move #0x2700,%sr" is actually disabling
> > all interrupts? And is m68k actually running irq handlers
> > with interrupts disabled?
> >
>
> When sonic_interrupt() executes, the IPL is 2 or 3 (since either IRQ may
> be involved). That is, SR & 0x700 is 0x200 or 0x300. The level 3 interrupt
> may interrupt execution of the level 2 handler so an irq lock is used to
> avoid re-entrance.
>
> This patch,
>
> diff --git a/drivers/net/ethernet/natsemi/sonic.c
> b/drivers/net/ethernet/natsemi/sonic.c
> index d17d1b4f2585..041354647bad 100644
> --- a/drivers/net/ethernet/natsemi/sonic.c
> +++ b/drivers/net/ethernet/natsemi/sonic.c
> @@ -355,6 +355,8 @@ static irqreturn_t sonic_interrupt(int irq, void *dev_id)
> */
> spin_lock_irqsave(&lp->lock, flags);
>
> + printk_once(KERN_INFO "%s: %08lx\n", __func__, flags);
> +
> status = SONIC_READ(SONIC_ISR) & SONIC_IMR_DEFAULT;
> if (!status) {
> spin_unlock_irqrestore(&lp->lock, flags);
>
> produces this output,
>
> [ 3.800000] sonic_interrupt: 00002300
I actually hope you can directly read the register rather than reading
a flag which might be a software one not from register.
>
> I ran that code in QEMU, but experience shows that Apple hardware works
> exactly the same. Please do confirm this for yourself, if you still think
> the code and comments in sonic_interrupt are wrong.
>
> > Best Regards
> > Barry
> >
Thanks
Barry
