Re: [PATCH v2 4/4] Revert "lockdep: Annotate lockdep assertions for context analysis"

[Bart Van Assche <bvanassche@acm.org>]

On 2/25/26 10:40 AM, Marco Elver wrote:
> On Wed, 25 Feb 2026 at 19:33, Bart Van Assche <bvanassche@acm.org> wrote:
>>
>> lockdep_assert_held() supports all data structures that have a member
>> with the name dep_map. __assume_ctx_lock() only supports data structures
>> that support lock context annotation. Remove __assume_ctx_lock() from
>> lockdep_assert_held(). This patch fixes the following build errors if
>> lock context analysis is enabled for the entire kernel tree:
>>
>> drivers/tty/tty_ldisc.c:451:2: error: call to '__assume_ctx_lock' is ambiguous
>>    451 |         lockdep_assert_held_write(&tty->ldisc_sem);
>>        |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> drivers/tty/tty_ldisc.c:451:2: error: call to '__assume_ctx_lock' is ambiguous
>>    451 |         lockdep_assert_held_write(&tty->ldisc_sem);
>>        |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> I think that's a hint that that we should just ld_semaphore a
> first-class context_lock_struct. That will enable the analysis for all
> ld_semaphore users.

This seems to be sufficient to solve the build errors if patch 4/4 is 
dropped:

diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index b5a5f32fdfd1..9be0a2c8bb40 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -192,6 +192,7 @@ struct kernfs_elem_attr {
   * accessible.  Dereferencing elem or any other outer entity requires
   * active reference.
   */
+context_lock_struct(kernfs_node);
  struct kernfs_node {
         atomic_t                count;
         atomic_t                active;
diff --git a/include/linux/tty_ldisc.h b/include/linux/tty_ldisc.h
index c5cccc3fc1e8..2977873b84c5 100644
--- a/include/linux/tty_ldisc.h
+++ b/include/linux/tty_ldisc.h
@@ -14,6 +14,7 @@ struct tty_struct;
  /*
   * the semaphore definition
   */
+context_lock_struct(ld_semaphore);
  struct ld_semaphore {
         atomic_long_t           count;
         raw_spinlock_t          wait_lock;

Bart.