ppc 8270, kernel 2.6.21.7
I took the following steps:
In a system call function , say , sys_reboot, interrupt was disabled
by local_irq_disable.
Then , value at the address of 0xc000050 was set to a value , say ,
0x1234. Code was like this :
sys_reboot()
{
local_irq_disable();
*(volatile unsigned long * )0xc1000050 = 0x1234;
while(1)
{
;
}
}
Finally, I reset the board (with power still on) into uboot,using
'md 0x1000050' to display the content at physical address 0x1000050,
and found that , it was not 0x1234.
However, if I delete the local_irq_disable() in sys_reboot, everything
went well---After I reset the board, 'md 0x1000050' return the value
0x1234.
So, this really puzzled me , could someone explain why this happed? Thank you.
PS:
static inline unsigned long local_irq_disable(void)
{
unsigned long flags, zero;
__asm__ __volatile__("li %1,0; lbz %0,%2(13); stb %1,%2(13)"
: "=r" (flags), "=&r" (zero)
: "i" (offsetof(struct paca_struct, soft_enabled))
: "memory");
return flags;
}
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