Messages in this thread | | | Subject | What reassert_nmi() in default_do_nmi() is for? | From | Huang Ying <> | Date | Mon, 30 Aug 2010 16:56:34 +0800 |
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Hi, All,
When reading NMI handler code, I find there is reassert_nmi() in the end of default_do_nmi(). And it is only called if the reason & 0xc0 != 0 (reason = inb(0x61)).
The comments for it is as follow:
/* * Reassert NMI in case it became active meanwhile * as it's edge-triggered: */ reassert_nmi();
The implementation of reassert_nmi is as follow:
static inline void reassert_nmi(void) { int old_reg = -1;
if (do_i_have_lock_cmos()) old_reg = current_lock_cmos_reg(); else lock_cmos(0); /* register doesn't matter here */ outb(0x8f, 0x70); inb(0x71); /* dummy */ outb(0x0f, 0x70); inb(0x71); /* dummy */ if (old_reg >= 0) outb(old_reg, 0x70); else unlock_cmos(); }
I can not understand the code and the logic. Can anyone explain it in more detail?
Thanks, Huang Ying
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