From a1eb1cdf4e55e1ecdb4a474070450d8a648686bf Mon Sep 17 00:00:00 2001 From: Finn Thain Date: Sat, 27 Jan 2018 18:51:40 -0500 Subject: m68k/mac: Fix apparent race condition in Baboon interrupt dispatch The algorithm used in baboon_irq() appears to be subject to a race condition: an IRQ flag could be lost if asserted between the MOV instructions from and to the interrupt flag register. However, testing shows that the write to the flag register has no effect. Rewrite this loop to remove the apparent race condition. No-one seems to know how to clear Baboon IRQ flags, or whether that's even possible, so add a comment about this. Tested-by: Stan Johnson Signed-off-by: Finn Thain Signed-off-by: Geert Uytterhoeven --- arch/m68k/mac/baboon.c | 27 ++++++++------------------- 1 file changed, 8 insertions(+), 19 deletions(-) (limited to 'arch/m68k') diff --git a/arch/m68k/mac/baboon.c b/arch/m68k/mac/baboon.c index c7ea6475ef9b..a7d280220662 100644 --- a/arch/m68k/mac/baboon.c +++ b/arch/m68k/mac/baboon.c @@ -18,10 +18,6 @@ int baboon_present; static volatile struct baboon *baboon; -#if 0 -extern int macide_ack_intr(struct ata_channel *); -#endif - /* * Baboon initialization. */ @@ -41,33 +37,26 @@ void __init baboon_init(void) } /* - * Baboon interrupt handler. This works a lot like a VIA. + * Baboon interrupt handler. + * XXX how do you clear a pending IRQ? is it even necessary? */ static void baboon_irq(struct irq_desc *desc) { - int irq_bit, irq_num; - unsigned char events; + short events, irq_bit; + int irq_num; events = baboon->mb_ifr & 0x07; - if (!events) - return; - irq_num = IRQ_BABOON_0; irq_bit = 1; do { - if (events & irq_bit) { - baboon->mb_ifr &= ~irq_bit; + if (events & irq_bit) { + events &= ~irq_bit; generic_handle_irq(irq_num); } + ++irq_num; irq_bit <<= 1; - irq_num++; - } while(events >= irq_bit); -#if 0 - if (baboon->mb_ifr & 0x02) macide_ack_intr(NULL); - /* for now we need to smash all interrupts */ - baboon->mb_ifr &= ~events; -#endif + } while (events); } /* -- cgit v1.2.3