---------- Forwarded message ----------
From: अनुज <anuj01@xxxxxxxxx>
Date: 2009/7/9
Subject: Re: Kernel Panic : Kernel BUG at rmap:479
To: Mulyadi Santosa <mulyadi.santosa@xxxxxxxxx>
Cc: Aniket Agashe <agasheac@xxxxxxxxx>, deveshs@xxxxxxx
Thanks in advance
--
Anuj Aggarwal
.''`.
: :Ⓐ : # apt-get install hakuna-matata
`. `'`
`-
From: अनुज <anuj01@xxxxxxxxx>
Date: 2009/7/9
Subject: Re: Kernel Panic : Kernel BUG at rmap:479
To: Mulyadi Santosa <mulyadi.santosa@xxxxxxxxx>
Cc: Aniket Agashe <agasheac@xxxxxxxxx>, deveshs@xxxxxxx
2009/7/8 Mulyadi Santosa <mulyadi.santosa@xxxxxxxxx>
To post the whole code is not possible for me right now. I can explain the steps what m doing :
In kernel space module :
1. A character driver having open,mmap and close fops.
2. In open(), a structure object (say struct test{....} of arround 100 bytes) is kmalloc-ed.
3. In mmap(), remap_page_range() is used to map the that 'struct test' structure object.
4. In close(), deallocated the 'struct test' using kfree().
In user space application :
1. opened the character device file using open().
2. mmap-ed the struct test object using mmap().
3. then, unmaped the struct test using munmap().
4. And, closed the device file using close().
5. Repeated the above steps in loop.
While running the application I have fired multiple instances of that user space application.
But after some iterations it is failing with that kernel panic message.
What is the meaning of the '...page is still there, but the address is no longer
exist' ?
means that memory is freed to slab allocator? and i don't need to explicitly free that memory with kfree().?
I tried without freeing the 'struct test' in close() in kernel space.
But there was memory leak until the whole RAM is consumed. And i got the same panic message after that.
2009/7/8 अनुज <anuj01@xxxxxxxxx>:
> Hi All<oops message truncated..>
>
> I am trying to map a buffer allocated with kmalloc to user space using
> mmap() and immediately unmapping that with munmap() in a loop for some
> testing purpose.
>
> But I get the kernel panic after some time (means after some iterations of
> the above loop) with message below :
Could you please post or upload the code somewhere? So we all here
might have a chance to take a closer look...
To post the whole code is not possible for me right now. I can explain the steps what m doing :
In kernel space module :
1. A character driver having open,mmap and close fops.
2. In open(), a structure object (say struct test{....} of arround 100 bytes) is kmalloc-ed.
3. In mmap(), remap_page_range() is used to map the that 'struct test' structure object.
4. In close(), deallocated the 'struct test' using kfree().
In user space application :
1. opened the character device file using open().
2. mmap-ed the struct test object using mmap().
3. then, unmaped the struct test using munmap().
4. And, closed the device file using close().
5. Repeated the above steps in loop.
While running the application I have fired multiple instances of that user space application.
But after some iterations it is failing with that kernel panic message.
Meanwhile, my guess is, since you do munmap(), you actually also do
kfree() on the kmalloc()-ed page. IIRC, do_unmap in kernel space
eventually put the page back to free slab/slub/slob (of its size). In
other word, the page is still there, but the address is no longer
exist. And this leads to the oops, possibly on the next mmap or
munmap.
What is the meaning of the '...page is still there, but the address is no longer
exist' ?
means that memory is freed to slab allocator? and i don't need to explicitly free that memory with kfree().?
I tried without freeing the 'struct test' in close() in kernel space.
But there was memory leak until the whole RAM is consumed. And i got the same panic message after that.
CMIIW people.
regards,
Mulyadi
Thanks in advance
--
Anuj Aggarwal
.''`.
: :Ⓐ : # apt-get install hakuna-matata
`. `'`
`-
--
Anuj Aggarwal
.''`.
: :Ⓐ : # apt-get install hakuna-matata
`. `'`
`-
