[tip: locking/urgent] locking: Make rwsem_assert_held_write_nolockdep() build with PREEMPT_RT=y

[tip-bot2 for Sebastian Andrzej Siewior]

The following commit has been merged into the locking/urgent branch of tip:

Commit-ID:     fa1f51162338b3e2f520d4bfedc42b3b2e00da6d
Gitweb:        https://git.kernel.org/tip/fa1f51162338b3e2f520d4bfedc42b3b2e00da6d
Author:        Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
AuthorDate:    Tue, 19 Mar 2024 19:20:50 +01:00
Committer:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Mon, 08 Apr 2024 16:39:16 +02:00

locking: Make rwsem_assert_held_write_nolockdep() build with PREEMPT_RT=y

The commit cited below broke the build for PREEMPT_RT because
rwsem_assert_held_write_nolockdep() passes a struct rw_semaphore but
rw_base_assert_held_write() expects struct rwbase_rt. Fixing the type alone
leads to the problem that WARN_ON() is not found because bug.h is missing.

In order to resolve this:

 - Keep the assert (WARN_ON()) in rwsem.h (not rwbase_rt.h)

 - Make rwsem_assert_held_write_nolockdep() do the implementation
   specific (rw_base) writer check.

 - Replace the "inline" with __always_inline which was used before.

Fixes: f70405afc99b1 ("locking: Add rwsem_assert_held() and rwsem_assert_held_write()")
Reported-by: Clark Williams <williams@xxxxxxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Waiman Long <longman@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240319182050.U4AzUF3I@xxxxxxxxxxxxx
---
 include/linux/rwbase_rt.h | 4 ++--
 include/linux/rwsem.h     | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/linux/rwbase_rt.h b/include/linux/rwbase_rt.h
index 29c4e4f..f2394a4 100644
--- a/include/linux/rwbase_rt.h
+++ b/include/linux/rwbase_rt.h
@@ -31,9 +31,9 @@ static __always_inline bool rw_base_is_locked(const struct rwbase_rt *rwb)
 	return atomic_read(&rwb->readers) != READER_BIAS;
 }
 
-static inline void rw_base_assert_held_write(const struct rwbase_rt *rwb)
+static __always_inline bool rw_base_is_write_locked(const struct rwbase_rt *rwb)
 {
-	WARN_ON(atomic_read(&rwb->readers) != WRITER_BIAS);
+	return atomic_read(&rwb->readers) == WRITER_BIAS;
 }
 
 static __always_inline bool rw_base_is_contended(const struct rwbase_rt *rwb)
diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
index 4f1c189..c8b543d 100644
--- a/include/linux/rwsem.h
+++ b/include/linux/rwsem.h
@@ -167,14 +167,14 @@ static __always_inline int rwsem_is_locked(const struct rw_semaphore *sem)
 	return rw_base_is_locked(&sem->rwbase);
 }
 
-static inline void rwsem_assert_held_nolockdep(const struct rw_semaphore *sem)
+static __always_inline void rwsem_assert_held_nolockdep(const struct rw_semaphore *sem)
 {
 	WARN_ON(!rwsem_is_locked(sem));
 }
 
-static inline void rwsem_assert_held_write_nolockdep(const struct rw_semaphore *sem)
+static __always_inline void rwsem_assert_held_write_nolockdep(const struct rw_semaphore *sem)
 {
-	rw_base_assert_held_write(sem);
+	WARN_ON(!rw_base_is_write_locked(&sem->rwbase));
 }
 
 static __always_inline int rwsem_is_contended(struct rw_semaphore *sem)