From fd3634312a04f336dcbfb481060219f0cd320738 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Sat, 7 Feb 2026 14:27:05 +0100 Subject: debugobject: Make it work with deferred page initialization - again debugobjects uses __GFP_HIGH for allocations as it might be invoked within locked regions. That worked perfectly fine until v6.18. It still works correctly when deferred page initialization is disabled and works by chance when no page allocation is required before deferred page initialization has completed. Since v6.18 allocations w/o a reclaim flag cause new_slab() to end up in alloc_frozen_pages_nolock_noprof(), which returns early when deferred page initialization has not yet completed. As the deferred page initialization takes quite a while the debugobject pool is depleted and debugobjects are disabled. This can be worked around when PREEMPT_COUNT is enabled as that allows debugobjects to add __GFP_KSWAPD_RECLAIM to the GFP flags when the context is preemtible. When PREEMPT_COUNT is disabled the context is unknown and the reclaim bit can't be set because the caller might hold locks which might deadlock in the allocator. In preemptible context the reclaim bit is harmless and not a performance issue as that's usually invoked from slow path initialization context. That makes debugobjects depend on PREEMPT_COUNT || !DEFERRED_STRUCT_PAGE_INIT. Fixes: af92793e52c3 ("slab: Introduce kmalloc_nolock() and kfree_nolock().") Signed-off-by: Thomas Gleixner Tested-by: Sebastian Andrzej Siewior Acked-by: Alexei Starovoitov Acked-by: Vlastimil Babka Link: https://patch.msgid.link/87pl6gznti.ffs@tglx --- lib/Kconfig.debug | 1 + 1 file changed, 1 insertion(+) (limited to 'lib/Kconfig.debug') diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index ba36939fda79..a874146ad828 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -723,6 +723,7 @@ source "mm/Kconfig.debug" config DEBUG_OBJECTS bool "Debug object operations" + depends on PREEMPT_COUNT || !DEFERRED_STRUCT_PAGE_INIT depends on DEBUG_KERNEL help If you say Y here, additional code will be inserted into the -- cgit v1.2.3