cvs commit: src/lib/libc/stdlib malloc.c

[Jason Evans]

On Jan 14, 2006, at 1:32 PM, Giorgos Keramidas wrote:
> On 2006-01-13 11:07, Jason Evans <jasone at FreeBSD.org> wrote:
>> On Jan 12, 2006, at 5:29 PM, Giorgos Keramidas wrote:
>>> Does it look like I'm right in thinking that this is a bug in Emacs?
>>
>> This looks like a bug in emacs, as you say, but I don't know if it
>> has any particular relation to the posix_memalign() changes.
>
> Apparently it does seem related to posix_memalign() changes.
> When I bootstrap Emacs without posix_memalign(), by manually
> tweaking src/config.h after configure runs, and #undef
> POSIX_MEMALIGN, then it passes the bootstrap stage normally.

Hmm, that's interesting.  I'll mess around with emacs later on today  
(though I only have i386 hardware at the moment).  Right now, I'm  
still building xorg on my machine in order to try to reproduce the  
gtk problems that Pascal Hofstee reported.

>> If updating to either before or after the broken
>> posix_memalign() revision, and need help figuring out the
>> issue, please let me know.
>
> More issues come up after updating to today's CURRENT version of
> malloc.  In particular:
>
>     irssi started core dumping with symptoms similar to those of
>     Emacs bootstrap, i.e. access to memory regions that are
>     <inaccessible> in gdb

malloc's ability to output allocation logs when run via ktrace, in  
combination with a core dump, should be able to show precisely what  
is happening.  If you're interested in tracking this down, I can help  
you.  Otherwise, can you give me a bit more information on the  
conditions that cause the crash?

The amd64 computer I have on order won't be here for at least another  
week, so if this is amd64-specific, I won't be able to reproduce it  
right away.

>     xorg-server-snap is a requirement in FreeBSD/amd64, but it
>     seems to trigger a panic and an insta-reboot with an ATI
>     Radeon here.

Chances are good that the video driver is assuming page alignment for  
a large malloc'ed block.  Right now, I don't have any suggestions on  
how to 100% verify this, but I'm planning to make some changes to  
malloc in the next couple of days that will allow us to use  
MALLOC_OPTIONS flags to determine if this is the problem.

> Apart from looking at the source code, do we
> have some sort of 'design' docs for the new malloc(), to see if I
> can help debug these problems a bit more when I restore my
> laptop's ports & packages from the backup later tonight?

I have a draft of a paper that I submitted to BSDcan, but I don't  
think I should make it generally available yet, as a courtesy to  
BSDcan.  I don't see a problem with providing it to individuals upon  
request, though.

Thanks,
Jason