Andrew Morton wrote:
On Wed, 15 Nov 2006 07:57:45 -0800
Badari Pulavarty <pbadari@xxxxxxxxxx> wrote:
We are looking at a customer situation (on 2.6.16-based distro) - where
system becomes almost useless while running some java & stress tests.
Root cause seems to be taking a pagefault in generic_file_buffered_write
() after calling prepare_write. I am wondering
1) Why & How this can happen - since we made sure to fault the user
buffer before prepare write.
When using writev() we only fault in the first segment of the iovec. If
the second or succesive segment isn't mapped into pagetables we're
vulnerable to the deadlock.
Hmm.. Not it :(
Its coming from write() not writev().
[C00000002ABBF290] [C00000000039D58C] .do_page_fault+0x2e4/0x75c
[C00000002ABBF460] [C000000000004860] .handle_page_fault+0x20/0x54
--- Exception: 301 at .__copy_tofrom_user+0x11c/0x580
LR = .generic_file_buffered_write+0x39c/0x7c8
[C00000002ABBF750] [C000000000095A94]
.generic_file_buffered_write+0x2c0/0x7c8 (
unreliable)
[C00000002ABBF8F0] [C0000000000962EC]
.__generic_file_aio_write_nolock+0x350/0x3
e0
[C00000002ABBFA20] [C000000000096908] .generic_file_aio_write+0x78/0x104
[C00000002ABBFAE0] [C0000000001649F0] .ext3_file_write+0x2c/0xd4
[C00000002ABBFB70] [C0000000000C5168] .do_sync_write+0xd4/0x130
[C00000002ABBFCF0] [C0000000000C5ED4] .vfs_write+0x128/0x20c
[C00000002ABBFD90] [C0000000000C664C] .sys_write+0x4c/0x8c
[C00000002ABBFE30] [C00000000000871C] syscall_exit+0x0/0x40
Thanks,
Badari
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