Hi Fernando,
On Tue, Apr 7, 2009 at 10:26 PM, Guzman Lugo, Fernando <[email protected]> wrote:
>
> Hi,
>
> Patch updated wit the fix in page_count(pg).
>
>
> From a5ab7e038b72e62358279ef3c4e64b2f260ceeee Mon Sep 17 00:00:00 2001
> From: Hari Kanigeri <[email protected]>
> Date: Thu, 26 Mar 2009 15:47:50 -0500
> Subject: [PATCH] DSPBRIDGE: Memory lock for DMM.
>
> Lock down the pages that are mapped to DSP virtual memory to prevent from
> getting swapped out
>
> Signed-off-by: Hari Kanigeri <[email protected]>
> ---
> + if (pfn_valid(__phys_to_pfn(patemp))) {
> + pg = phys_to_page(patemp);
> + get_page(pg);
get_page() makes sure that page->count is not zero and atomically increments it.
That means after execution of get_page(); page->count will be always 1
or greater
than 1.
If this is the case then what is the point of having following code?
if (page_count(pg) < 1) <-- This will always evaluate to FALSE.
> + if (page_count(pg) < 1) {
> + printk(KERN_EMERG "DSPBRIDGE:MAP "
> + "function: COUNT 0 FOR PA "
> + "0x%x\n", patemp);
> + printk(KERN_EMERG "Bad page state"
> + "in process '%s'\n"
> + "page:%p flags:0x%0*lx "
> + "mapping:%p mapcount:%d "
> + "count:%d\n"
> + "Trying to fix it up, but "
> + "a reboot is needed\n"
> + "Backtrace:\n",
> + current->comm, pg,
> + (int)(2*sizeof(unsigned
> long)),
> + (unsigned long)pg->flags,
> + pg->mapping,
> page_mapcount(pg),
> + page_count(pg));
> + dump_stack();
> + BUG_ON(1);
> + }
Cheers,
Ameya.
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