Re: [patch] Real-Time Preemption, -VP-2.6.9-rc4-mm1-U3

[Ingo Molnar]

* Dominik Karall <dominik.karall@xxxxxxx> wrote:

> i'm not sure if this bug depends on preemption patch, or if it is a
> general one in -mm1 tree.
> 
> kernel BUG at fs/fat/cache.c:150!

> EIP is at fat_cache_add+0x135/0x151

> Process mplayer (pid: 9843, threadinfo=ce414000 task=c8128a20)

> Call Trace:
>  [<c01a11bb>] fat_get_cluster+0x11f/0x1de
>  [<c01a12c1>] fat_bmap_cluster+0x47/0x98
>  [<c01a13f1>] fat_bmap+0xdf/0x101
>  [<c01a36e8>] fat_get_block+0x30/0x198
>  [<c0152866>] alloc_buffer_head+0x33/0x52
>  [<c01501ea>] create_buffers+0x51/0x86
>  [<c015141c>] block_read_full_page+0x1bd/0x2cc
>  [<c01a36b8>] fat_get_block+0x0/0x198
>  [<c0132f0c>] add_to_page_cache+0x58/0x6e
>  [<c013a0e4>] read_pages+0xbe/0x15e
>  [<c013a49c>] do_page_cache_readahead+0x120/0x19b
>  [<c013a606>] page_cache_readahead+0xef/0x1f8
>  [<c01336ab>] do_generic_mapping_read+0x133/0x54b
>  [<c013c911>] lru_cache_add+0xd/0x4f
>  [<c0133d53>] __generic_file_aio_read+0x1a3/0x218
>  [<c0133ac3>] file_read_actor+0x0/0xed
>  [<c0133ec5>] generic_file_read+0x9c/0xba
>  [<c012b84c>] _mutex_lock+0x20/0x36
>  [<c01244c8>] do_sigaction+0x1dc/0x1f7
>  [<c012b468>] autoremove_wake_function+0x0/0x43
>  [<c012b84c>] _mutex_lock+0x20/0x36
>  [<c0167974>] dnotify_parent+0x35/0x95
>  [<c014e0a9>] vfs_read+0xcd/0x126
>  [<c014e36f>] sys_read+0x41/0x6a
>  [<c0103f7b>] syscall_call+0x7/0xb

indeed this does not seem to be related to the preemption patch. How
hard is it to reproduce this problem? If it's easy then please try with
vanilla 2.6.9-rc4-mm1 (and if it breaks too, with 2.6.9-rc4 as well), to
narrow down where the breakage got introduced.

	Ingo
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