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review.shift-gmbh.com / SHIFTPHONES / kernel / common / 345c0b1cc49ef7ecf28f0430011a668ca7761f62
commit345c0b1cc49ef7ecf28f0430011a668ca7761f62[log] [tgz]
authorSaravana Kannan <saravanak@google.com>Wed Nov 04 12:54:30 2020 -0800
committerAlistair Delva <adelva@google.com>Wed Jan 06 00:30:59 2021 +0000
treece631a0031ef13e6bcae9b7e8ae20112389611ca
parentb56c9e4cdf09cd3ddf8ba5999b24c54a20d41b15 [diff]
UPSTREAM: driver core: Fix lockdep warning on wfs_lock

There's a potential deadlock with the following cycle:
wfs_lock --> device_links_lock --> kn->count

Fix this by simply dropping the lock around a list_empty() check that's
just exported to a sysfs file. The sysfs file output is an instantaneous
check anyway and the lock doesn't really add any protection.

Lockdep log:

[   48.808132]
[   48.808132] the existing dependency chain (in reverse order) is:
[   48.809069]
[   48.809069] -> #2 (kn->count){++++}:
[   48.809707]        __kernfs_remove.llvm.7860393000964815146+0x2d4/0x460
[   48.810537]        kernfs_remove_by_name_ns+0x54/0x9c
[   48.811171]        sysfs_remove_file_ns+0x18/0x24
[   48.811762]        device_del+0x2b8/0x5a8
[   48.812269]        __device_link_del+0x98/0xb8
[   48.812829]        device_links_driver_bound+0x210/0x2d8
[   48.813496]        driver_bound+0x44/0xf8
[   48.814000]        really_probe+0x340/0x6e0
[   48.814526]        driver_probe_device+0xb8/0x100
[   48.815117]        device_driver_attach+0x78/0xb8
[   48.815708]        __driver_attach+0xe0/0x194
[   48.816255]        bus_for_each_dev+0xa8/0x11c
[   48.816816]        driver_attach+0x24/0x30
[   48.817331]        bus_add_driver+0x100/0x1e0
[   48.817880]        driver_register+0x78/0x114
[   48.818427]        __platform_driver_register+0x44/0x50
[   48.819089]        0xffffffdbb3227038
[   48.819551]        do_one_initcall+0xd8/0x1e0
[   48.820099]        do_init_module+0xd8/0x298
[   48.820636]        load_module+0x3afc/0x44c8
[   48.821173]        __arm64_sys_finit_module+0xbc/0xf0
[   48.821807]        el0_svc_common+0xbc/0x1d0
[   48.822344]        el0_svc_handler+0x74/0x98
[   48.822882]        el0_svc+0x8/0xc
[   48.823310]
[   48.823310] -> #1 (device_links_lock){+.+.}:
[   48.824036]        __mutex_lock_common+0xe0/0xe44
[   48.824626]        mutex_lock_nested+0x28/0x34
[   48.825185]        device_link_add+0xd4/0x4ec
[   48.825734]        of_link_to_suppliers+0x158/0x204
[   48.826347]        of_fwnode_add_links+0x50/0x64
[   48.826928]        device_link_add_missing_supplier_links+0x90/0x11c
[   48.827725]        fw_devlink_resume+0x58/0x130
[   48.828296]        of_platform_default_populate_init+0xb4/0xd0
[   48.829030]        do_one_initcall+0xd8/0x1e0
[   48.829578]        do_initcall_level+0xb8/0xcc
[   48.830137]        do_basic_setup+0x60/0x7c
[   48.830662]        kernel_init_freeable+0x128/0x1ac
[   48.831275]        kernel_init+0x18/0x29c
[   48.831781]        ret_from_fork+0x10/0x18
[   48.832297]
[   48.832297] -> #0 (wfs_lock){+.+.}:
[   48.832922]        __lock_acquire+0xe04/0x2e20
[   48.833480]        lock_acquire+0xbc/0xec
[   48.833984]        __mutex_lock_common+0xe0/0xe44
[   48.834577]        mutex_lock_nested+0x28/0x34
[   48.835136]        waiting_for_supplier_show+0x3c/0x98
[   48.835781]        dev_attr_show+0x48/0xb4
[   48.836295]        sysfs_kf_seq_show+0xe8/0x184
[   48.836864]        kernfs_seq_show+0x48/0x8c
[   48.837401]        seq_read+0x1c8/0x600
[   48.837884]        kernfs_fop_read+0x68/0x204
[   48.838431]        __vfs_read+0x60/0x214
[   48.838925]        vfs_read+0xbc/0x15c
[   48.839397]        ksys_read+0x78/0xe4
[   48.839869]        __arm64_sys_read+0x1c/0x28
[   48.840416]        el0_svc_common+0xbc/0x1d0
[   48.840953]        el0_svc_handler+0x74/0x98
[   48.841490]        el0_svc+0x8/0xc
[   48.841917]
[   48.841917] other info that might help us debug this:
[   48.841917]
[   48.842920] Chain exists of:
[   48.842920]   wfs_lock --> device_links_lock --> kn->count
[   48.842920]
[   48.844152]  Possible unsafe locking scenario:
[   48.844152]
[   48.844895]        CPU0                    CPU1
[   48.845463]        ----                    ----
[   48.846032]   lock(kn->count);
[   48.846417]                                lock(device_links_lock);
[   48.847203]                                lock(kn->count);
[   48.847902]   lock(wfs_lock);
[   48.848276]
[   48.848276]  *** DEADLOCK ***

Reported-by: Cheng-Jui.Wang@mediatek.com
Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20201104205431.3795207-1-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Bug: 171536500
(cherry picked from commit 7008e58c63bc8468e8d16154e25d780198b3ecfc)
Change-Id: Icb98a270d6ff07bcc81a2162ac00493fae6fafe6
1 file changed
tree: ce631a0031ef13e6bcae9b7e8ae20112389611ca
  1. android/
  2. arch/
  3. block/
  4. certs/
  5. crypto/
  6. Documentation/
  7. drivers/
  8. fs/
  9. include/
  10. init/
  11. ipc/
  12. kernel/
  13. lib/
  14. LICENSES/
  15. mm/
  16. net/
  17. samples/
  18. scripts/
  19. security/
  20. sound/
  21. tools/
  22. usr/
  23. virt/
  24. .clang-format
  25. .cocciconfig
  26. .get_maintainer.ignore
  27. .gitattributes
  28. .gitignore
  29. .mailmap
  30. build.config.aarch64
  31. build.config.allmodconfig
  32. build.config.allmodconfig.aarch64
  33. build.config.allmodconfig.arm
  34. build.config.allmodconfig.x86_64
  35. build.config.arm
  36. build.config.common
  37. build.config.db845c
  38. build.config.gki
  39. build.config.gki-debug.aarch64
  40. build.config.gki-debug.x86_64
  41. build.config.gki.aarch64
  42. build.config.gki.x86_64
  43. build.config.gki_kasan
  44. build.config.gki_kasan.aarch64
  45. build.config.gki_kasan.x86_64
  46. build.config.x86_64
  47. COPYING
  48. CREDITS
  49. Kbuild
  50. Kconfig
  51. MAINTAINERS
  52. Makefile
  53. README
  54. README.md
README.md

How do I submit patches to Android Common Kernels

  1. BEST: Make all of your changes to upstream Linux. If appropriate, backport to the stable releases. These patches will be merged automatically in the corresponding common kernels. If the patch is already in upstream Linux, post a backport of the patch that conforms to the patch requirements below.

    • Do not send patches upstream that contain only symbol exports. To be considered for upstream Linux, additions of EXPORT_SYMBOL_GPL() require an in-tree modular driver that uses the symbol -- so include the new driver or changes to an existing driver in the same patchset as the export.
    • When sending patches upstream, the commit message must contain a clear case for why the patch is needed and beneficial to the community. Enabling out-of-tree drivers or functionality is not not a persuasive case.

  2. LESS GOOD: Develop your patches out-of-tree (from an upstream Linux point-of-view). Unless these are fixing an Android-specific bug, these are very unlikely to be accepted unless they have been coordinated with kernel-team@android.com. If you want to proceed, post a patch that conforms to the patch requirements below.

Common Kernel patch requirements

  • All patches must conform to the Linux kernel coding standards and pass script/checkpatch.pl
  • Patches shall not break gki_defconfig or allmodconfig builds for arm, arm64, x86, x86_64 architectures (see https://source.android.com/setup/build/building-kernels)
  • If the patch is not merged from an upstream branch, the subject must be tagged with the type of patch: UPSTREAM:, BACKPORT:, FROMGIT:, FROMLIST:, or ANDROID:.
  • All patches must have a Change-Id: tag (see https://gerrit-review.googlesource.com/Documentation/user-changeid.html)
  • If an Android bug has been assigned, there must be a Bug: tag.
  • All patches must have a Signed-off-by: tag by the author and the submitter

Additional requirements are listed below based on patch type

Requirements for backports from mainline Linux: UPSTREAM:, BACKPORT:

  • If the patch is a cherry-pick from Linux mainline with no changes at all
    • tag the patch subject with UPSTREAM:.
    • add upstream commit information with a (cherry picked from commit ...) line
    • Example:
      • if the upstream commit message is
        important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>
  • then Joe Smith would upload the patch for the common kernel as
        UPSTREAM: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        (cherry picked from commit c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
        Signed-off-by: Joe Smith <joe.smith@foo.org>
  • If the patch requires any changes from the upstream version, tag the patch with BACKPORT: instead of UPSTREAM:.
    • use the same tags as UPSTREAM:
    • add comments about the changes under the (cherry picked from commit ...) line
    • Example:
        BACKPORT: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        (cherry picked from commit c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
        [joe: Resolved minor conflict in drivers/foo/bar.c ]
        Signed-off-by: Joe Smith <joe.smith@foo.org>

Requirements for other backports: FROMGIT:, FROMLIST:,

  • If the patch has been merged into an upstream maintainer tree, but has not yet been merged into Linux mainline
    • tag the patch subject with FROMGIT:
    • add info on where the patch came from as (cherry picked from commit <sha1> <repo> <branch>). This must be a stable maintainer branch (not rebased, so don't use linux-next for example).
    • if changes were required, use BACKPORT: FROMGIT:
    • Example:
      • if the commit message in the maintainer tree is
        important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>
  • then Joe Smith would upload the patch for the common kernel as
        FROMGIT: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        (cherry picked from commit 878a2fd9de10b03d11d2f622250285c7e63deace
         https://git.kernel.org/pub/scm/linux/kernel/git/foo/bar.git test-branch)
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <joe.smith@foo.org>
  • If the patch has been submitted to LKML, but not accepted into any maintainer tree
    • tag the patch subject with FROMLIST:
    • add a Link: tag with a link to the submittal on lore.kernel.org
    • add a Bug: tag with the Android bug (required for patches not accepted into a maintainer tree)
    • if changes were required, use BACKPORT: FROMLIST:
    • Example:
        FROMLIST: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        Link: https://lore.kernel.org/lkml/20190619171517.GA17557@someone.com/
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <joe.smith@foo.org>

Requirements for Android-specific patches: ANDROID:

  • If the patch is fixing a bug to Android-specific code
    • tag the patch subject with ANDROID:
    • add a Fixes: tag that cites the patch with the bug
    • Example:
        ANDROID: fix android-specific bug in foobar.c

        This is the detailed description of the important fix

        Fixes: 1234abcd2468 ("foobar: add cool feature")
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <joe.smith@foo.org>
  • If the patch is a new feature
    • tag the patch subject with ANDROID:
    • add a Bug: tag with the Android bug (required for android-specific features)