[PATCH v6 1/2] debugobjects: Add a can_fill_pool() helper for debug_objects_fill_pool()

[Waiman Long <longman@redhat.com>]

The conditional check in debug_objects_fill_pool() for determining
if fill_pool() can be called is now quite complicated. Add a new
can_fill_pool() helper to break down the conditions individually to
make them easier to understand. No functional change is expected.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Waiman Long <longman@redhat.com>
---
 lib/debugobjects.c | 35 ++++++++++++++++++++++++++---------
 1 file changed, 26 insertions(+), 9 deletions(-)

diff --git a/lib/debugobjects.c b/lib/debugobjects.c
index b18a682fe3da..1d826689611f 100644
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -720,6 +720,30 @@ static inline bool debug_objects_is_pi_blocked_on(void)
 #endif
 }
 
+static inline bool can_fill_pool(void)
+{
+	/*
+	 * On !RT enabled kernels there are no restrictions and spinlock_t and
+	 * raw_spinlock_t are the same types.
+	 */
+	if (!IS_ENABLED(CONFIG_PREEMPT_RT))
+		return true;
+
+	/*
+	 * On RT enabled kernels the pool refill must happen in preemptible
+	 * context and the task must not be blocked on a lock as that could
+	 * corrupt the PI state when blocking on a lock in the allocation path.
+	 */
+	if (preemptible() && !debug_objects_is_pi_blocked_on())
+		return true;
+
+	/*
+	 * Allow refilling to happen early in the boot with disabled interrupts
+	 * as long as the scheduler is not operational.
+	 */
+	return system_state < SYSTEM_SCHEDULING;
+}
+
 static void debug_objects_fill_pool(void)
 {
 	if (!static_branch_likely(&obj_cache_enabled))
@@ -734,18 +758,11 @@ static void debug_objects_fill_pool(void)
 	if (likely(!pool_should_refill(&pool_global)))
 		return;
 
-	/*
-	 * On RT enabled kernels the pool refill must happen in preemptible
-	 * context and not enqueued on an rt_mutex -- for !RT kernels we rely
-	 * on the fact that spinlock_t and raw_spinlock_t are basically the
-	 * same type and this lock-type inversion works just fine.
-	 */
-	if (!IS_ENABLED(CONFIG_PREEMPT_RT) || system_state < SYSTEM_SCHEDULING ||
-	    (preemptible() && !debug_objects_is_pi_blocked_on())) {
+	if (can_fill_pool()) {
 		/*
 		 * Annotate away the spinlock_t inside raw_spinlock_t warning
 		 * by temporarily raising the wait-type to LD_WAIT_CONFIG, matching
-		 * the preemptible() condition above.
+		 * the preemptible() condition in can_fill_pool().
 		 */
 		static DEFINE_WAIT_OVERRIDE_MAP(fill_pool_map, LD_WAIT_CONFIG);
 		lock_map_acquire_try(&fill_pool_map);
-- 
2.54.0