mprotect(2) clears the flag for whole page which causes program crash.

[Julian Elischer]

Sharad Chandra wrote:
>  ,---- [Jung-uk Kim wrote:]
> | On Wednesday 18 November 2009 01:52 pm, Robert Watson wrote:
> | > On Tue, 17 Nov 2009, Sharad Chandra wrote:
> | > > Is it known bug or is there any workaround? How will a userland
> | > > process make sure that process will not crash as malloc(3) can
> | > > allocate where ever it get the memory free to use.
> | >
> | > mprotect(2) operates on pages, so you'll want to use mmap(2) and
> | > munmap(2) to allocate and free pages directly rather than
> | > mallac(3), which manages byte ranges from pages managed using those
> | > same interfaces.
> |
> | For example:
> |
> | http://docs.freebsd.org/cgi/mid.cgi?200911181926.nAIJQHOR081471
> |
> 
> Thanks everyone. mmap(2) worked and program did not crash. Only problem with 
> it I use only fraction of allocated memory (each request alocate minimum of 
> one page and my request is in hundreds), rest is waste of it so no one else 
> will get this memory to use. And if a process runs as daemon and makes many 
> request, It can hold a lot of it. Just a question floated in mind.

write your own allocator that efficiently divides up the mmapped pages 
among several requests?

> 
> Many thanks,
> Sharad Chandra
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