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debugobjects: Don't call fill_pool() in early boot hardirq context

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When booting a debug PREEMPT_RT kernel on an ARM64 system, a "inconsistent
{HARDIRQ-ON-W} -> {IN-HARDIRQ-W} usage" lockdep warning message was
reported to the console.

During early boot, interrupts are enabled before the scheduler is
enabled. In this window (before SYSTEM_SCHEDULING is set) interrupts can
fire and in the hard interrupt context handler attempt to fill the pool

This can lead to a deadlock when the interrupt occurred when the interrupt
hits a region which holds a lock that is required to be taken in the
allocation path.

Add a new can_fill_pool() helper and reorder the exception rule and forbid
this scenario by excluding allocations from hard interrupt context.

Fixes: 06e0ae988f ("debugobjects: Allow to refill the pool before SYSTEM_SCHEDULING")
Suggested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260605173038.495075-1-longman@redhat.com
This commit is contained in:
Waiman Long 2026-06-05 13:30:38 -04:00 • committed by Thomas Gleixner
commit 0d046ae106
1 changed files with 37 additions and 9 deletions
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46
lib/debugobjects.c
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@ -720,6 +720,41 @@ 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 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 (debug_objects_is_pi_blocked_on())
return false;
/*
* On RT enabled kernels the pool refill should happen in preemptible
* context.
*/
if (preemptible())
return true;
/*
* Though during system boot before scheduling is set up, preemption is
* disabled and the pool can get exhausted. Before scheduling is active
* a task cannot be blocked on a sleeping lock, but it might hold a lock
* and if interrupted then hard interrupt context might run into a lock
* inversion. So exclude hard interrupt context from allocations before
* scheduling is active.
*/
return system_state < SYSTEM_SCHEDULING && !in_hardirq();
}
static void debug_objects_fill_pool(void)
{
if (!static_branch_likely(&obj_cache_enabled))
@ -734,18 +769,11 @@ 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);