On 7/10/07, Robert P. J. Day <rpjday@xxxxxxxxxxxxxx> wrote:
i'm curious about this snippet from the above source file:
...
/* This is needed, because copy_page and memcpy are not usable for copying
* task structs.
*/
static inline void do_copy_page(long *dst, long *src)
{
int n;
for (n = PAGE_SIZE / sizeof(long); n; n--)
*dst++ = *src++;
}
...
and why not? what is it about copy_page or memcpy that makes it
unsuitable for copying task structs? thanks.
Check out this LKML message
http://www.ussg.iu.edu/hypermail/linux/kernel/0607.0/1886.html
"swsusp should not use memcpy for snapshotting memory, because on some
architectures memcpy may increase preempt_count. Then, as a result, wrong
value of preempt_count is stored in the image.
Replace memcpy in copy_data_pages with an open-coded loop."
rday
Bhanu
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Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
Waterloo, Ontario, CANADA
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