On Wed, 2003-06-11 at 06:06, Biswaranjan wrote: > hi.. > > we are trying to implement double buffering in the following > away. > > we have two buffers in the kernel.. > the user is able to mmap one buffer to the user space > using mmap() system call. > we have used remap_page_range() to setup the mapping.with one > buffer. > this is working fine > > sometimes it may be necessary for the kernel to map the other > buffer > to the user space (to the same virtual address) so that the > orginal mapped buffer can be dma transferred. > > to perform this new mapping we have again used > remap_page_range() > > but the kernel oops'es when this is done..as follows.. > > Jun 11 15:26:50 EMB kernel: forget_pte: old mapping existed! > Jun 11 15:26:50 EMB kernel: ------------[ cut here ]------------ > Jun 11 15:26:50 EMB kernel: kernel BUG at memory.c:461! > Jun 11 15:26:50 EMB kernel: invalid operand: 0000 > . > > i think we are supposed to remove the old mappings > with zap_page_range()..but since we are compiling as a module > this function is inaccessible (dont know why) I believe the zap_page_range() will do the trick. As for it not being exported, yeah, that would be a pain. You could either 1) export it in your own kernel(s), or 2) submit a patch to have it exported in official releases. You'll still need to do #1 in the short term. -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
