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 <tobin@xxxxxxxxxx> > > AuthorDate: Fri Mar 29 10:01:23 2019 +1100 > > Commit: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> > > 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-tobin@xxxxxxxxxx > > Signed-off-by: Tobin C. Harding <tobin@xxxxxxxxxx> > > Cc: Christoph Lameter <cl@xxxxxxxxx> > > Cc: David Rientjes <rientjes@xxxxxxxxxx> > > Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> > > Cc: Pekka Enberg <penberg@xxxxxxxxxx> > > Cc: Roman Gushchin <guro@xxxxxx> > > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > > Signed-off-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> > > > > 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 (ffffffffaeeb71b0), but was ffffcee1406d3f70. (prev=ffffcee140422508). > > 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.
