[linux-next:master] [lib/Kconfig.debug] 888c290a02: BUG:MAX_LOCKDEP_CHAINS_too_low

From: kernel test robot

Date: Sun May 31 2026 - 04:53:18 EST

Hello,

this report is just FYI.

as we understand, this is a debug patch. and by it, we notice below config diff:

--- /pkg/linux/x86_64-randconfig-161-20260529/gcc-14/e66d61ddb1d8504e4bfd3dcc3fa26293f9d14d9d/.config 2026-05-30 00:10:22.784053022 +0800
+++ /pkg/linux/x86_64-randconfig-161-20260529/gcc-14/888c290a0240da1ce1a4d69beafe44f9abec93c0/.config 2026-05-29 23:38:02.317371800 +0800
@@ -97,6 +97,7 @@ CONFIG_HRTIMER_REARM_DEFERRED=y
CONFIG_HAVE_POSIX_CPU_TIMERS_TASK_WORK=y
CONFIG_POSIX_CPU_TIMERS_TASK_WORK=y
CONFIG_CONTEXT_TRACKING=y
+CONFIG_CONTEXT_TRACKING_IDLE=y

#
# Timers subsystem
@@ -129,7 +130,8 @@ CONFIG_PREEMPT_BUILD=y
CONFIG_ARCH_HAS_PREEMPT_LAZY=y
# CONFIG_PREEMPT is not set
CONFIG_PREEMPT_LAZY=y
-# CONFIG_PREEMPT_RT is not set
+CONFIG_PREEMPT_RT=y
+CONFIG_PREEMPT_RT_NEEDS_BH_LOCK=y
CONFIG_PREEMPT_COUNT=y
CONFIG_PREEMPTION=y
# CONFIG_PREEMPT_DYNAMIC is not set
@@ -150,9 +152,11 @@ CONFIG_PSI=y
#
# RCU Subsystem
#
-CONFIG_TINY_RCU=y
+CONFIG_TREE_RCU=y
+CONFIG_PREEMPT_RCU=y
CONFIG_RCU_EXPERT=y
-CONFIG_TINY_SRCU=y
+CONFIG_TREE_SRCU=y
+# CONFIG_FORCE_NEED_SRCU_NMI_SAFE is not set
CONFIG_TASKS_RCU_GENERIC=y
CONFIG_FORCE_TASKS_RCU=y
CONFIG_NEED_TASKS_RCU=y
@@ -162,7 +166,18 @@ CONFIG_TASKS_RUDE_RCU=y
CONFIG_FORCE_TASKS_TRACE_RCU=y
CONFIG_TASKS_TRACE_RCU=y
CONFIG_TASKS_TRACE_RCU_NO_MB=y
+CONFIG_RCU_STALL_COMMON=y
CONFIG_RCU_NEED_SEGCBLIST=y
+CONFIG_RCU_FANOUT=64
+CONFIG_RCU_FANOUT_LEAF=2
+CONFIG_RCU_BOOST=y
+CONFIG_RCU_BOOST_DELAY=500
+CONFIG_RCU_EXP_KTHREAD=y
+CONFIG_RCU_NOCB_CPU=y
+# CONFIG_RCU_NOCB_CPU_DEFAULT_ALL is not set
+# CONFIG_RCU_NOCB_CPU_CB_BOOST is not set
+CONFIG_RCU_LAZY=y
+# CONFIG_RCU_LAZY_DEFAULT_OFF is not set
# CONFIG_RCU_DOUBLE_CHECK_CB_TIME is not set
# end of RCU Subsystem

@@ -176,7 +191,6 @@ CONFIG_HAVE_UNSTABLE_SCHED_CLOCK=y
#
# Scheduler features
#
-# CONFIG_SCHED_PROXY_EXEC is not set
# end of Scheduler features

CONFIG_ARCH_SUPPORTS_NUMA_BALANCING=y
@@ -772,7 +786,6 @@ CONFIG_MODULES_USE_ELF_RELA=y
CONFIG_ARCH_HAS_EXECMEM_ROX=y
CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK=y
CONFIG_HAVE_SOFTIRQ_ON_OWN_STACK=y
-CONFIG_SOFTIRQ_ON_OWN_STACK=y
CONFIG_ARCH_HAS_ELF_RANDOMIZE=y
CONFIG_HAVE_ARCH_MMAP_RND_BITS=y
CONFIG_HAVE_EXIT_THREAD=y
@@ -974,7 +987,6 @@ CONFIG_MMU_NOTIFIER=y
CONFIG_DEFAULT_MMAP_MIN_ADDR=4096
CONFIG_ARCH_WANT_GENERAL_HUGETLB=y
CONFIG_ARCH_WANTS_THP_SWAP=y
-# CONFIG_TRANSPARENT_HUGEPAGE is not set
CONFIG_PAGE_MAPCOUNT=y
CONFIG_PGTABLE_HAS_HUGE_LEAVES=y
CONFIG_HAVE_GIGANTIC_FOLIOS=y
@@ -4202,9 +4214,9 @@ CONFIG_DRM_ETNAVIV_THERMAL=y
# CONFIG_DRM_GMA500 is not set
CONFIG_DRM_GUD=y
CONFIG_DRM_HISI_HIBMC=y
-# CONFIG_DRM_I915 is not set
# CONFIG_DRM_LOGICVC is not set
CONFIG_DRM_MGAG200=y
+CONFIG_DRM_MGAG200_DISABLE_WRITECOMBINE=y
CONFIG_DRM_NOUVEAU=y
CONFIG_NOUVEAU_DEBUG=5
CONFIG_NOUVEAU_DEBUG_DEFAULT=3
@@ -4895,7 +4907,6 @@ CONFIG_LEDS_TRIGGER_DISK=y
CONFIG_LEDS_TRIGGER_MTD=y
CONFIG_LEDS_TRIGGER_HEARTBEAT=y
CONFIG_LEDS_TRIGGER_BACKLIGHT=y
-# CONFIG_LEDS_TRIGGER_CPU is not set
CONFIG_LEDS_TRIGGER_ACTIVITY=y
CONFIG_LEDS_TRIGGER_GPIO=y
CONFIG_LEDS_TRIGGER_DEFAULT_ON=y
@@ -7388,7 +7399,6 @@ CONFIG_HARDLOCKUP_CHECK_TIMESTAMP=y
CONFIG_DETECT_HUNG_TASK=y
CONFIG_DEFAULT_HUNG_TASK_TIMEOUT=480
CONFIG_BOOTPARAM_HUNG_TASK_PANIC=0
-CONFIG_DETECT_HUNG_TASK_BLOCKER=y
CONFIG_WQ_WATCHDOG=y
CONFIG_BOOTPARAM_WQ_STALL_PANIC=0
# CONFIG_WQ_CPU_INTENSIVE_REPORT is not set
@@ -7415,9 +7425,7 @@ CONFIG_PROVE_RAW_LOCK_NESTING=y
# CONFIG_LOCK_STAT is not set
CONFIG_DEBUG_RT_MUTEXES=y
CONFIG_DEBUG_SPINLOCK=y
-CONFIG_DEBUG_MUTEXES=y
CONFIG_DEBUG_WW_MUTEX_SLOWPATH=y
-CONFIG_DEBUG_RWSEMS=y
CONFIG_DEBUG_LOCK_ALLOC=y
CONFIG_LOCKDEP=y
CONFIG_LOCKDEP_BITS=15
@@ -7463,8 +7471,13 @@ CONFIG_RCU_TORTURE_TEST_CHK_RDR_STATE=y
# CONFIG_RCU_TORTURE_TEST_LOG_CPU is not set
CONFIG_RCU_TORTURE_TEST_LOG_GP=y
CONFIG_RCU_REF_SCALE_TEST=m
+CONFIG_RCU_CPU_STALL_TIMEOUT=21
+CONFIG_RCU_EXP_CPU_STALL_TIMEOUT=0
+CONFIG_RCU_CPU_STALL_CPUTIME=y
+CONFIG_RCU_CPU_STALL_NOTIFIER=y
CONFIG_RCU_TRACE=y
CONFIG_RCU_EQS_DEBUG=y
+CONFIG_RCU_STRICT_GRACE_PERIOD=y
# CONFIG_RCU_DYNTICKS_TORTURE is not set
# CONFIG_TRIVIAL_PREEMPT_RCU is not set
# end of RCU Debugging

then we notice issues as below full report.
just FYI what we observed in our tests.

kernel test robot noticed "BUG:MAX_LOCKDEP_CHAINS_too_low" on:

commit: 888c290a0240da1ce1a4d69beafe44f9abec93c0 ("lib/Kconfig.debug: enable CONFIG_PREEMPT_RT for syzbot kernels.")
https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master

[test failed on linux-next/master f7af91adc230aa99e23330ecf85bc9badd9780ad]

in testcase: trinity
version: trinity-i386-abe9de86-1_20230429
with following parameters:

runtime: 300s
group: group-04
nr_groups: 5

config: x86_64-randconfig-161-20260529
compiler: gcc-14
test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 32G

(please refer to attached dmesg/kmsg for entire log/backtrace)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-lkp/202605311625.72d32001-lkp@xxxxxxxxx

[ 467.321357][ T4078] BUG: MAX_LOCKDEP_CHAINS too low!
[ 467.321374][ T4078] turning off the locking correctness validator.
[ 467.321400][ T4078] CPU: 0 UID: 65534 PID: 4078 Comm: trinity-main Tainted: G T 7.1.0-rc5-00005-g888c290a0240 #1 PREEMPT_{RT,LAZY}
[ 467.321419][ T4078] Tainted: [T]=RANDSTRUCT
[ 467.321431][ T4078] Call Trace:
[ 467.321436][ T4078] <TASK>
[ 467.321443][ T4078] dump_stack_lvl (dump_stack.c:94 dump_stack.c:120)
[ 467.321482][ T4078] dump_stack (dump_stack.c:129)
[ 467.321492][ T4078] add_chain_cache (locking/lockdep.c:3755)
[ 467.321512][ T4078] validate_chain (locking/lockdep.c:3857 locking/lockdep.c:3878)
[ 467.321526][ T4078] __lock_acquire (locking/lockdep.c:5239)
[ 467.321539][ T4078] ? lock_hrtimer_base+0x32/0x80
[ 467.321552][ T4078] lock_acquire (locking/lockdep.c:5870)
[ 467.321561][ T4078] ? lock_hrtimer_base+0x32/0x80
[ 467.321574][ T4078] ? __lock_acquire (locking/lockdep.c:5239)
[ 467.321588][ T4078] _raw_spin_lock_irqsave (linux/spinlock_api_smp.h:132 (discriminator 1) locking/spinlock.c:166 (discriminator 1))
[ 467.321609][ T4078] ? lock_hrtimer_base+0x32/0x80
[ 467.321621][ T4078] lock_hrtimer_base+0x32/0x80
[ 467.321633][ T4078] hrtimer_start_range_ns (time/hrtimer.c:1489)
[ 467.321645][ T4078] ? __hrtimer_start_range_ns (time/hrtimer.c:1460)
[ 467.321658][ T4078] ? kvm_clock_read (x86/kernel/kvmclock.c:80 (discriminator 1))
[ 467.321672][ T4078] hrtick_cond_restart (linux/hrtimer.h:220 sched/core.c:924)
[ 467.321684][ T4078] hrtick_schedule_exit+0x2c/0x80
[ 467.321695][ T4078] finish_task_switch+0x38f/0x540
[ 467.321708][ T4078] ? finish_task_switch+0x376/0x540
[ 467.321723][ T4078] __schedule (sched/core.c:5391 sched/core.c:7189)
[ 467.321738][ T4078] ? io_schedule_timeout (sched/core.c:8102)
[ 467.321753][ T4078] ? might_alloc (linux/sched/mm.h:317)
[ 467.321766][ T4078] preempt_schedule_notrace (sched/core.c:7463)
[ 467.321779][ T4078] preempt_schedule_notrace_thunk (x86/entry/thunk.S:13)
[ 467.321795][ T4078] rcu_is_watching (rcu/tree.c:753 (discriminator 1))
[ 467.321807][ T4078] lock_acquire (trace/events/lock.h:24 (discriminator 11) locking/lockdep.c:5833 (discriminator 11))
[ 467.321817][ T4078] ? kernfs_fop_open (kernfs/file.c:619)
[ 467.321828][ T4078] ? lock_acquire (locking/lockdep.c:5870)
[ 467.321837][ T4078] ? kernfs_fop_open (linux/slab.h:950 linux/slab.h:1188 kernfs/file.c:641)
[ 467.321846][ T4078] __fs_reclaim_acquire (page_alloc.c:4325)
[ 467.321857][ T4078] ? might_alloc (linux/sched/mm.h:317)
[ 467.321867][ T4078] fs_reclaim_acquire (page_alloc.c:4339 (discriminator 1))
[ 467.321877][ T4078] might_alloc (linux/sched/mm.h:317)
[ 467.321887][ T4078] __kmalloc_cache_noprof (slub.c:4521 slub.c:4876 slub.c:5415)
[ 467.321902][ T4078] kernfs_fop_open (linux/slab.h:950 linux/slab.h:1188 kernfs/file.c:641)
[ 467.321916][ T4078] ? kernfs_fop_release (kernfs/file.c:789)
[ 467.321924][ T4078] do_dentry_open (open.c:947)
[ 467.321941][ T4078] vfs_open (open.c:1079)
[ 467.321952][ T4078] do_open (namei.c:4699)
[ 467.321969][ T4078] path_openat (namei.c:4858)
[ 467.321980][ T4078] ? kernel_tmpfile_open (namei.c:4800)
[ 467.321992][ T4078] ? rt_mutex_slowunlock (locking/rtmutex.c:350 locking/rtmutex.c:1463)
[ 467.322007][ T4078] do_file_open (namei.c:4887)
[ 467.322018][ T4078] ? path_openat (namei.c:4875)
[ 467.322032][ T4078] ? mark_wakeup_next_waiter (locking/rtmutex.c:1364)
[ 467.322063][ T4078] do_sys_openat2 (open.c:1364 (discriminator 1))
[ 467.322075][ T4078] ? file_open_root (open.c:1352)
[ 467.322090][ T4078] ? __lock_acquire (locking/lockdep.c:5239)
[ 467.322102][ T4078] do_sys_open (open.c:1370)
[ 467.322113][ T4078] ? filp_open (open.c:1340)
[ 467.322124][ T4078] ? vtime_user_exit (sched/cputime.c:743 (discriminator 1))
[ 467.322136][ T4078] ? __lock_release+0x4e/0x140
[ 467.322149][ T4078] __ia32_compat_sys_openat (open.c:1432 open.c:1430 open.c:1430)
[ 467.322162][ T4078] ia32_sys_call (kbuild/obj/consumer/x86_64-randconfig-161-20260529/./arch/x86/include/generated/asm/syscalls_32.h:296)
[ 467.322174][ T4078] __do_fast_syscall_32 (x86/entry/syscall_32.c:83 x86/entry/syscall_32.c:307)
[ 467.322186][ T4078] ? preempt_latency_start (linux/ftrace.h:1168 sched/core.c:5837)
[ 467.322198][ T4078] ? __do_fast_syscall_32 (linux/randomize_kstack.h:58 x86/entry/syscall_32.c:279)
[ 467.322210][ T4078] do_fast_syscall_32 (x86/entry/syscall_32.c:332)
[ 467.322220][ T4078] do_SYSENTER_32 (x86/entry/syscall_32.c:370)
[ 467.322229][ T4078] entry_SYSENTER_compat_after_hwframe (x86/entry/entry_64_compat.S:126)
[ 467.322241][ T4078] RIP: 0023:0xf7fb938c
[ 467.322252][ T4078] Code: d2 74 05 c1 e8 0c 89 02 8b 5d fc 31 c0 c9 31 d2 31 c9 c3 cc 90 90 90 90 90 90 90 90 90 90 0f 1f 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90
All code
========
0: d2 74 05 c1 shlb %cl,-0x3f(%rbp,%rax,1)
4: e8 0c 89 02 8b call 0xffffffff8b028915
9: 5d pop %rbp
a: fc cld
b: 31 c0 xor %eax,%eax
d: c9 leave
e: 31 d2 xor %edx,%edx
10: 31 c9 xor %ecx,%ecx
12: c3 ret
13: cc int3
14: 90 nop
15: 90 nop
16: 90 nop
17: 90 nop
18: 90 nop
19: 90 nop
1a: 90 nop
1b: 90 nop
1c: 90 nop
1d: 90 nop
1e: 0f 1f 00 nopl (%rax)
21: 51 push %rcx
22: 52 push %rdx
23: 55 push %rbp
24: 89 e5 mov %esp,%ebp
26: 0f 34 sysenter
28: cd 80 int $0x80
2a:* 5d pop %rbp <-- trapping instruction
2b: 5a pop %rdx
2c: 59 pop %rcx
2d: c3 ret
2e: cc int3
2f: 90 nop
30: 90 nop
31: 90 nop
32: 90 nop
33: 90 nop
34: 90 nop
35: 90 nop
36: 90 nop
37: 90 nop
38: 90 nop
39: 90 nop
3a: 90 nop
3b: 90 nop
3c: 90 nop
3d: 90 nop
3e: 90 nop
3f: 90 nop

Code starting with the faulting instruction
===========================================
0: 5d pop %rbp
1: 5a pop %rdx
2: 59 pop %rcx
3: c3 ret
4: cc int3
5: 90 nop
6: 90 nop
7: 90 nop
8: 90 nop
9: 90 nop
a: 90 nop
b: 90 nop
c: 90 nop
d: 90 nop
e: 90 nop
f: 90 nop
10: 90 nop
11: 90 nop
12: 90 nop
13: 90 nop
14: 90 nop
15: 90 nop

The kernel config and materials to reproduce are available at:
https://download.01.org/0day-ci/archive/20260531/202605311625.72d32001-lkp@xxxxxxxxx

--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki