samples: enhance hung_task detector test with read-write semaphore support

Extend the hung_task detector test module to include read-write semaphore
support alongside existing mutex and semaphore tests.  This module now
creates additional debugfs files under <debugfs>/hung_task, namely
'rw_semaphore_read' and 'rw_semaphore_write', in addition to 'mutex' and
'semaphore'.  Reading these files with multiple processes triggers a
prolonged sleep (256 seconds) while holding the respective lock, enabling
hung_task detector testing for various locking mechanisms.

This change builds on the extensible hung_task_tests module, adding
read-write semaphore functionality to improve test coverage for kernel
locking primitives.  The implementation ensures proper lock handling and
includes checks to prevent redundant data reads.

Usage is:

        > cd /sys/kernel/debug/hung_task
        > cat mutex & cat mutex           # Test mutex blocking
        > cat semaphore & cat semaphore   # Test semaphore blocking
        > cat rw_semaphore_write \
            & cat rw_semaphore_read       # Test rwsem blocking
        > cat rw_semaphore_write \
            & cat rw_semaphore_write      # Test rwsem blocking

Update the Kconfig description to reflect the addition of read-write
semaphore debugfs files.

Link: https://lkml.kernel.org/r/20250627072924.36567-4-lance.yang@linux.dev
Signed-off-by: Zi Li <zi.li@linux.dev>
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Anna Schumaker <anna.schumaker@oracle.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joel Granados <joel.granados@kernel.org>
Cc: John Stultz <jstultz@google.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Mingzhe Yang <mingzhe.yang@ly.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tomasz Figa <tfiga@chromium.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yongliang Gao <leonylgao@tencent.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

samples/Kconfig

@@ -316,10 +316,9 @@ config SAMPLE_HUNG_TASK
 	depends on DETECT_HUNG_TASK && DEBUG_FS
 	help
 	  Build a module that provides debugfs files (e.g., mutex, semaphore,
-	  etc.) under <debugfs>/hung_task. If user reads one of these files,
-	  it will sleep long time (256 seconds) with holding a lock. Thus,
-	  if 2 or more processes read the same file concurrently, it will
-	  be detected by the hung_task watchdog.
+	  rw_semaphore_read, rw_semaphore_write) under <debugfs>/hung_task.
+	  Reading these files with multiple processes triggers hung task
+	  detection by holding locks for a long time (256 seconds).
 
 source "samples/rust/Kconfig"