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- Fix potential debugobjects deadlock on PREEMPT_RT kernels

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(Waiman Long)
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'core-urgent-2026-06-13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull debugobjects fix from Ingo Molnar:

 - Fix potential debugobjects deadlock on PREEMPT_RT kernels (Waiman
   Long)

* tag 'core-urgent-2026-06-13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  debugobjects: Don't call fill_pool() in early boot hardirq context
This commit is contained in:
Linus Torvalds 2026-06-13 08:23:36 -07:00
commit 2b07ea76fd
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);