Panic when starting X with Intel KMS

[Gustau Pérez i Querol]

> The issue happened somewhere before the process exit.  Try the patch
> below, the idea is that your overflow count is really big, so the
> wrong-doer could cause underflow when acting.
>
> diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
> index 19be4e0..fcdc6af 100644
> --- a/sys/amd64/amd64/pmap.c
> +++ b/sys/amd64/amd64/pmap.c
> @@ -465,6 +465,9 @@ pmap_resident_count_dec(pmap_t pmap, int count)
>   {
>   
>   	PMAP_LOCK_ASSERT(pmap, MA_OWNED);
> +	KASSERT(pmap->pm_stats.resident_count >= count,
> +	    ("pmap %p resident count underflow %ld %d", pmap,
> +	    pmap->pm_stats.resident_count, count));
>   	pmap->pm_stats.resident_count -= count;
>   }
>   
    Hi,

    the assert doesn't happen (that's resident_count is not bigger than 
count). You can find the complete core at:

       https://dl.dropboxusercontent.com/u/2094962/core.txt.5

    I'm no expert on that, but would this mean that the process, while 
freeying mem, causes the kernel to free more maps than the process has?

    Any other info during the panic, let me know (I have a second 
machine and I can connect to it via serial port).

    OTOH, in puzzled because the stack gets corrupted an thus I can't 
check which is the offending process (I don't know if that would be of 
any use in this situation).  It is my understanding that isn't the 
process who should be fixed but the kernel side. In this case the stack 
corruption isn't that very important (at least this is what I think), 
but sometimes it is very handy.


-- 
    Salut i força,

    Gustau

---------------------------------------------------------------------------
Prou top-posting :	http://ca.wikipedia.org/wiki/Top-posting
Stop top-posting :	http://en.wikipedia.org/wiki/Posting_style	

O O O Gustau Pérez i Querol
O O O Unitat de Gestió dels departaments
O O O Matemàtica Aplicada IV i Enginyeria Telemàtica

       Universitat Politècnica de Catalunya
       Edifici C3 - Despatx S101-B
  UPC  Campus Nord UPC
       C/ Jordi Girona, 1-3
       08034 - Barcelona