Re: [LKP] dd2283f260 [ 97.263072] WARNING:at_kernel/locking/lockdep.c:#lock_downgrade

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 





On 11/20/18 4:57 PM, Kirill A. Shutemov wrote:
On Fri, Nov 16, 2018 at 08:56:04AM -0800, Yang Shi wrote:
a8dda165ec  vfree: add debug might_sleep()
dd2283f260  mm: mmap: zap pages with read mmap_sem in munmap
5929a1f0ff  Merge tag 'riscv-for-linus-4.20-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/palmer/riscv-linux
0bc80e3cb0  Add linux-next specific files for 20181114
+-----------------------------------------------------+------------+------------+------------+---------------+
|                                                     | a8dda165ec | dd2283f260 | 5929a1f0ff | next-20181114 |
+-----------------------------------------------------+------------+------------+------------+---------------+
| boot_successes                                      | 314        | 178        | 190        | 168           |
| boot_failures                                       | 393        | 27         | 21         | 40            |
| WARNING:held_lock_freed                             | 383        | 23         | 17         | 39            |
| is_freeing_memory#-#,with_a_lock_still_held_there   | 383        | 23         | 17         | 39            |
| BUG:unable_to_handle_kernel                         | 5          | 2          | 4          | 1             |
| Oops:#[##]                                          | 9          | 3          | 4          | 1             |
| EIP:debug_check_no_locks_freed                      | 9          | 3          | 4          | 1             |
| Kernel_panic-not_syncing:Fatal_exception            | 9          | 3          | 4          | 1             |
| Mem-Info                                            | 4          | 1          |            |               |
| invoked_oom-killer:gfp_mask=0x                      | 1          | 1          |            |               |
| WARNING:at_kernel/locking/lockdep.c:#lock_downgrade | 0          | 6          | 4          | 7             |
| EIP:lock_downgrade                                  | 0          | 6          | 4          | 7             |
+-----------------------------------------------------+------------+------------+------------+---------------+

[   96.288009] random: get_random_u32 called from arch_rnd+0x3c/0x70 with crng_init=0
[   96.359626] input_id (331) used greatest stack depth: 6360 bytes left
[   96.749228] grep (358) used greatest stack depth: 6336 bytes left
[   96.921470] network.sh (341) used greatest stack depth: 6212 bytes left
[   97.262340]
[   97.262587] =========================
[   97.263072] WARNING: held lock freed!
[   97.263536] 4.19.0-06969-gdd2283f #1 Not tainted
[   97.264110] -------------------------
[   97.264575] udevd/198 is freeing memory 9c16c930-9c16c99b, with a lock still held there!
[   97.265542] (ptrval) (&anon_vma->rwsem){....}, at: unlink_anon_vmas+0x14e/0x420
[   97.266450] 1 lock held by udevd/198:
[   97.266924]  #0: (ptrval) (&mm->mmap_sem){....}, at: __do_munmap+0x531/0x730
I have not figured out what this is caused by. But, the below warning looks
more confusing. This might be caused by the below one.
I *think* we need to understand more about what detached VMAs mean for
rmap. The anon_vma for these VMAs still reachable for the rmap and
therefore VMA too. I don't quite grasp what is implications of this, but
it doesn't look good.

I'm supposed before accessing anon_vma, VMA need to be found by find_vma() first, right? But, finding VMA need hold mmap_sem, once detach VMAs is called, others should not be able to find the VMAs anymore. So, the anon_vma should not be reachable except the munmap caller.


I'll look into this more when I get some free cycles.

I'm still traveling, will definitely look into it further once I'm back.

Thanks,
Yang


It's better to disable the optimization for now (by ignoring 'downgrade'
in __do_munmap()). Before it hits release.





[Index of Archives]     [Linux ARM Kernel]     [Linux ARM]     [Linux Omap]     [Fedora ARM]     [IETF Annouce]     [Bugtraq]     [Linux OMAP]     [Linux MIPS]     [eCos]     [Asterisk Internet PBX]     [Linux API]

  Powered by Linux