2:07 a.m.
在 2021/8/13 下午1:53, Jiri Slaby 写道:
Hi,
On 12. 08. 21, 14:26, kernel test robot wrote:
>>> drivers/tty/hvc/hvc_console.c:190:26: warning: variable 'hp' is
>>> uninitialized when used here [-Wuninitialized]
> spin_unlock_irqrestore(&hp->c_lock, flags);
> ^~
> drivers/tty/hvc/hvc_console.c:149:23: note: initialize the
> variable 'hp' to silence this warning
> struct hvc_struct *hp;
> ^
> = NULL
So you clearly didn't test your change as it would crash quite
instantly. I wonder, where do you intend to get hp from in the
console::print() hook?
thanks,
According to analysis, this issue may can be solved just by adjust the
alignment to L1_CACHE_BYTES:
#define __ALIGNED__ __attribute__((__aligned__(L1_CACHE_BYTES)))
Our analysis as below, the original __ALIGNED__ is sizeof(long) which is
8 for 64bit cpu.
char c[N_OUTBUF] __ALIGNED__; //c[16] __ALIGNED__;
For 4K page, c[16] may cross the page when alignemnt is 8.
In the case the physical address of c[16] is noncontiguous.
|------8----|..........|-----8-----| PAGE_1
..........................|-----------16----------| c[16]
.........................................|-----8-----|.............|-----8-----|
PAGE_2
But when the alignment is L1_CACHE_BYTES(eg, 64), or at least
N_OUTBUF(16), we have no dma issue as c[16] won't cross the page, the
physical address of c[16] is contiguous.
|--------64--------|.........|--------64---------| PAGE_3
..................................|--c[16]--|
Could you help comments this? thanks