From: Waiman Long Date: Fri, 5 Jun 2026 17:30:38 +0000 (-0400) Subject: debugobjects: Don't call fill_pool() in early boot hardirq context X-Git-Tag: v7.1~3^2 X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=0d046ae106255cba5eb83b23f78ee93f3620247d;p=thirdparty%2Fkernel%2Flinux.git debugobjects: Don't call fill_pool() in early boot hardirq context 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: 06e0ae988f6e ("debugobjects: Allow to refill the pool before SYSTEM_SCHEDULING") Suggested-by: Sebastian Andrzej Siewior Suggested-by: Thomas Gleixner Signed-off-by: Waiman Long Signed-off-by: Thomas Gleixner Reviewed-by: Sebastian Andrzej Siewior Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260605173038.495075-1-longman@redhat.com --- diff --git a/lib/debugobjects.c b/lib/debugobjects.c index 772ddabcbe7d3..1fa156c45c09b 100644 --- a/lib/debugobjects.c +++ b/lib/debugobjects.c @@ -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);