On Wed, Apr 03, 2019 at 03:54:17PM +1100, Tobin C. Harding wrote:
> On Wed, Apr 03, 2019 at 10:00:38AM +0800, kernel test robot wrote:
> > Greetings,
> >
> > 0day kernel testing robot got the below dmesg and the first bad commit is
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> >
> > commit 15c8410c67adefd26ea0df1f1b86e1836051784b
> > Author: Tobin C. Harding
> > AuthorDate: Fri Mar 29 10:01:23 2019 +1100
> > Commit: Stephen Rothwell
> > CommitDate: Sat Mar 30 16:09:41 2019 +1100
> >
> > mm/slob.c: respect list_head abstraction layer
> >
> > Currently we reach inside the list_head. This is a violation of the
> > layer
> > of abstraction provided by the list_head. It makes the code fragile.
> > More importantly it makes the code wicked hard to understand.
> >
> > The code logic is based on the page in which an allocation was made, we
> > want to modify the slob_list we are working on to have this page at the
> > front. We already have a function to check if an entry is at the front
> > of
> > the list. Recently a function was added to list.h to do the list
> > rotation. We can use these two functions to reduce line count, reduce
> > code fragility, and reduce cognitive load required to read the code.
> >
> > Use list_head functions to interact with lists thereby maintaining the
> > abstraction provided by the list_head structure.
> >
> > Link: http://lkml.kernel.org/r/20190318000234.22049-3-to...@kernel.org
> > Signed-off-by: Tobin C. Harding
> > Cc: Christoph Lameter
> > Cc: David Rientjes
> > Cc: Joonsoo Kim
> > Cc: Pekka Enberg
> > Cc: Roman Gushchin
> > Signed-off-by: Andrew Morton
> > Signed-off-by: Stephen Rothwell
> >
> > 2e1f88301e include/linux/list.h: add list_rotate_to_front()
> > 15c8410c67 mm/slob.c: respect list_head abstraction layer
> > 05d08e2995 Add linux-next specific files for 20190402
> > +---+++---+
> > | | 2e1f88301e |
> > 15c8410c67 | next-20190402 |
> > +---+++---+
> > | boot_successes| 1009 | 198
> > | 299 |
> > | boot_failures | 0 | 2
> > | 44|
> > | WARNING:at_lib/list_debug.c:#__list_add_valid | 0 | 2
> > | 44|
> > | RIP:__list_add_valid | 0 | 2
> > | 44|
> > | WARNING:at_lib/list_debug.c:#__list_del_entry_valid | 0 | 2
> > | 25|
> > | RIP:__list_del_entry_valid| 0 | 2
> > | 25|
> > | WARNING:possible_circular_locking_dependency_detected | 0 | 2
> > | 44|
> > | RIP:_raw_spin_unlock_irqrestore | 0 | 2
> > | 2 |
> > | BUG:kernel_hang_in_test_stage | 0 | 0
> > | 6 |
> > | BUG:unable_to_handle_kernel | 0 | 0
> > | 1 |
> > | Oops:#[##]| 0 | 0
> > | 1 |
> > | RIP:slob_page_alloc | 0 | 0
> > | 1 |
> > | Kernel_panic-not_syncing:Fatal_exception | 0 | 0
> > | 1 |
> > | RIP:delay_tsc | 0 | 0
> > | 2 |
> > +---+++---+
> >
> > [2.618737] db_root: cannot open: /etc/target
> > [2.620114] mtdoops: mtd device (mtddev=name/number) must be supplied
> > [2.620967] slram: not enough parameters.
> > [2.621614] [ cut here ]
> > [2.622254] list_add corruption. prev->next should be next
> > (aeeb71b0), but was cee1406d3f70. (prev=cee140422508).
>
> Is this perhaps a false positive because we hackishly move the list_head
> 'head' and insert it back into the list. Perhaps this is confusing the
> validation functions?
This has got me stumped. I cannot create a test case where manipulating
a list with list_rotate_to_front() causes the list validation functions
to emit an error. Also I cannot come up with a way on paper that it can
happen either.
I don't really know how to go forwards from here. I'll sleep on it and
see if something comes to me, any ideas to look into please?
thanks,
Tobin.
