> -----Original Message----- > From: Finn Thain [mailto:fthain@xxxxxxxxxxxxxxxxxxx] > Sent: Friday, February 12, 2021 1:09 PM > To: Song Bao Hua (Barry Song) <song.bao.hua@xxxxxxxxxxxxx> > Cc: tanxiaofei <tanxiaofei@xxxxxxxxxx>; jejb@xxxxxxxxxxxxx; > martin.petersen@xxxxxxxxxx; linux-scsi@xxxxxxxxxxxxxxx; > linux-kernel@xxxxxxxxxxxxxxx; linuxarm@xxxxxxxxxxxxx; > linux-m68k@xxxxxxxxxxxxxxx > Subject: RE: Re: [PATCH for-next 00/32] spin lock usage optimization for SCSI > drivers > > On Fri, 12 Feb 2021, Song Bao Hua (Barry Song) wrote: > > > > > > -----Original Message----- > > > From: Finn Thain [mailto:fthain@xxxxxxxxxxxxxxxxxxx] > > > Sent: Friday, February 12, 2021 12:57 PM > > > To: Song Bao Hua (Barry Song) <song.bao.hua@xxxxxxxxxxxxx> > > > Cc: tanxiaofei <tanxiaofei@xxxxxxxxxx>; jejb@xxxxxxxxxxxxx; > > > martin.petersen@xxxxxxxxxx; linux-scsi@xxxxxxxxxxxxxxx; > > > linux-kernel@xxxxxxxxxxxxxxx; linuxarm@xxxxxxxxxxxxx; > > > linux-m68k@xxxxxxxxxxxxxxx > > > 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. > > > > Again, the implementation of arch_local_irq_save() may be found in > arch/m68k/include/asm/irqflags.h Yes. I have read it. Anyway, I started a discussion in genirq with you cc-ed: https://lore.kernel.org/lkml/c46ddb954cfe45d9849c911271d7ec23@xxxxxxxxxxxxx/ And thanks very much for all your efforts to help me understand M68k. Let's get this clarified thoroughly in genirq level. In arm, we also have some special high-priority interrupts which are not NMI but able to preempt normal IRQ. They are managed by arch-extended APIs rather than common APIs. Neither arch_irqs_disabled() nor local_irq_disable() API can access this kind of interrupts. They are using things specific to ARM like: local_fiq_disable() local_fiq_enable() set_fiq_handler() disable_fiq() enable_fiq() ... so fiq doesn't bother us anyhow in genirq. > > > > > > > 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
