[paulmckrcu:dev.2025.08.21a] [rcu] 8bd9383727: WARNING:possible_circular_locking_dependency_detected

[kernel test robot <oliver.sang@intel.com>]

hi, Paul,

the similar issue still exists on this dev.2025.08.21a branch.
again, if the issue is already fixed on later branches, please just ignore.
thanks


Hello,

kernel test robot noticed "WARNING:possible_circular_locking_dependency_detected" on:

commit: 8bd9383727068a5a18acfecefbdfa44a7d6bd838 ("rcu: Re-implement RCU Tasks Trace in terms of SRCU-fast")
https://github.com/paulmckrcu/linux dev.2025.08.21a

in testcase: rcutorture
version: 
with following parameters:

	runtime: 300s
	test: default
	torture_type: tasks-tracing



config: x86_64-randconfig-003-20250824
compiler: clang-20
test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G

(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@intel.com>
| Closes: https://lore.kernel.org/oe-lkp/202508261642.b15eefbb-lkp@intel.com


[   42.365933][  T393] WARNING: possible circular locking dependency detected
[   42.366428][  T393] 6.17.0-rc1-00035-g8bd938372706 #1 Tainted: G                T
[   42.366985][  T393] ------------------------------------------------------
[   42.367490][  T393] rcu_torture_rea/393 is trying to acquire lock:
[ 42.367952][ T393] ffffffffad41dc88 (rcu_tasks_trace_srcu_struct.srcu_wq.lock){....}-{2:2}, at: swake_up_one (kernel/sched/swait.c:52 (discriminator 1)) 
[   42.368775][  T393]
[   42.368775][  T393] but task is already holding lock:
[ 42.369278][ T393] ffff88813d1ff2e8 (&p->pi_lock){-.-.}-{2:2}, at: rcutorture_one_extend (kernel/rcu/rcutorture.c:?) rcutorture 
[   42.370043][  T393]
[   42.370043][  T393] which lock already depends on the new lock.
[   42.370043][  T393]
[   42.370755][  T393]
[   42.370755][  T393] the existing dependency chain (in reverse order) is:
[   42.371388][  T393]
[   42.371388][  T393] -> #1 (&p->pi_lock){-.-.}-{2:2}:
[ 42.371903][ T393] _raw_spin_lock_irqsave (include/linux/spinlock_api_smp.h:110 kernel/locking/spinlock.c:162) 
[ 42.372309][ T393] try_to_wake_up (include/linux/spinlock.h:557 (discriminator 1) kernel/sched/core.c:4216 (discriminator 1)) 
[ 42.372669][ T393] swake_up_locked (include/linux/list.h:111) 
[ 42.373029][ T393] swake_up_one (kernel/sched/swait.c:54 (discriminator 1)) 
[ 42.373380][ T393] tasks_tracing_torture_read_unlock (include/linux/srcu.h:408 (discriminator 1) include/linux/rcupdate_trace.h:81 (discriminator 1) kernel/rcu/rcutorture.c:1112 (discriminator 1)) rcutorture 
[ 42.373952][ T393] rcutorture_one_extend (kernel/rcu/rcutorture.c:2141) rcutorture 
[ 42.374452][ T393] rcu_torture_one_read_end (kernel/rcu/rcutorture.c:2357) rcutorture 
[ 42.374976][ T393] rcu_torture_one_read (kernel/rcu/rcutorture.c:?) rcutorture 
[ 42.375460][ T393] rcu_torture_reader (kernel/rcu/rcutorture.c:2443) rcutorture 
[ 42.375920][ T393] kthread (kernel/kthread.c:465) 
[ 42.376241][ T393] ret_from_fork (arch/x86/kernel/process.c:154) 
[ 42.376603][ T393] ret_from_fork_asm (arch/x86/entry/entry_64.S:255) 
[   42.376973][  T393]
[   42.376973][  T393] -> #0 (rcu_tasks_trace_srcu_struct.srcu_wq.lock){....}-{2:2}:
[ 42.377657][ T393] __lock_acquire (kernel/locking/lockdep.c:3166) 
[ 42.378031][ T393] lock_acquire (kernel/locking/lockdep.c:5868) 
[ 42.378378][ T393] _raw_spin_lock_irqsave (include/linux/spinlock_api_smp.h:110 kernel/locking/spinlock.c:162) 
[ 42.378794][ T393] swake_up_one (kernel/sched/swait.c:52 (discriminator 1)) 
[ 42.379152][ T393] tasks_tracing_torture_read_unlock (include/linux/srcu.h:408 (discriminator 1) include/linux/rcupdate_trace.h:81 (discriminator 1) kernel/rcu/rcutorture.c:1112 (discriminator 1)) rcutorture 
[ 42.379714][ T393] rcutorture_one_extend (kernel/rcu/rcutorture.c:2141) rcutorture 
[ 42.380217][ T393] rcu_torture_one_read_end (kernel/rcu/rcutorture.c:2357) rcutorture 
[ 42.380731][ T393] rcu_torture_one_read (kernel/rcu/rcutorture.c:?) rcutorture 
[ 42.381220][ T393] rcu_torture_reader (kernel/rcu/rcutorture.c:2443) rcutorture 
[ 42.381714][ T393] kthread (kernel/kthread.c:465) 
[ 42.382060][ T393] ret_from_fork (arch/x86/kernel/process.c:154) 
[ 42.382420][ T393] ret_from_fork_asm (arch/x86/entry/entry_64.S:255) 
[   42.382796][  T393]
[   42.382796][  T393] other info that might help us debug this:
[   42.382796][  T393]
[   42.383515][  T393]  Possible unsafe locking scenario:
[   42.383515][  T393]
[   42.384052][  T393]        CPU0                    CPU1
[   42.384428][  T393]        ----                    ----
[   42.384799][  T393]   lock(&p->pi_lock);
[   42.385083][  T393]                                lock(rcu_tasks_trace_srcu_struct.srcu_wq.lock);
[   42.385707][  T393]                                lock(&p->pi_lock);
[   42.386180][  T393]   lock(rcu_tasks_trace_srcu_struct.srcu_wq.lock);
[   42.386663][  T393]
[   42.386663][  T393]  *** DEADLOCK ***
[   42.386663][  T393]
[   42.387236][  T393] 1 lock held by rcu_torture_rea/393:
[ 42.387626][ T393] #0: ffff88813d1ff2e8 (&p->pi_lock){-.-.}-{2:2}, at: rcutorture_one_extend (kernel/rcu/rcutorture.c:?) rcutorture 
[   42.388419][  T393]
[   42.388419][  T393] stack backtrace:
[   42.388852][  T393] CPU: 0 UID: 0 PID: 393 Comm: rcu_torture_rea Tainted: G                T   6.17.0-rc1-00035-g8bd938372706 #1 PREEMPT(full)
[   42.389758][  T393] Tainted: [T]=RANDSTRUCT
[   42.390057][  T393] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
[   42.390786][  T393] Call Trace:
[   42.391020][  T393]  <TASK>
[ 42.391225][ T393] dump_stack_lvl (lib/dump_stack.c:123 (discriminator 2)) 
[ 42.391544][ T393] print_circular_bug (kernel/locking/lockdep.c:2045) 
[ 42.391898][ T393] check_noncircular (kernel/locking/lockdep.c:?) 
[ 42.392242][ T393] __lock_acquire (kernel/locking/lockdep.c:3166) 
[ 42.392594][ T393] ? __schedule (kernel/sched/sched.h:1531 (discriminator 1) kernel/sched/core.c:6969 (discriminator 1)) 
[ 42.392930][ T393] ? lock_release (kernel/locking/lockdep.c:470 (discriminator 3)) 
[ 42.393272][ T393] ? swake_up_one (kernel/sched/swait.c:52 (discriminator 1)) 
[ 42.393610][ T393] lock_acquire (kernel/locking/lockdep.c:5868) 
[ 42.393930][ T393] ? swake_up_one (kernel/sched/swait.c:52 (discriminator 1)) 
[ 42.394264][ T393] _raw_spin_lock_irqsave (include/linux/spinlock_api_smp.h:110 kernel/locking/spinlock.c:162) 
[ 42.394640][ T393] ? swake_up_one (kernel/sched/swait.c:52 (discriminator 1)) 
[ 42.394969][ T393] swake_up_one (kernel/sched/swait.c:52 (discriminator 1)) 
[ 42.395281][ T393] tasks_tracing_torture_read_unlock (include/linux/srcu.h:408 (discriminator 1) include/linux/rcupdate_trace.h:81 (discriminator 1) kernel/rcu/rcutorture.c:1112 (discriminator 1)) rcutorture 
[ 42.395814][ T393] rcutorture_one_extend (kernel/rcu/rcutorture.c:2141) rcutorture 
[ 42.396276][ T393] rcu_torture_one_read_end (kernel/rcu/rcutorture.c:2357) rcutorture 
[ 42.396756][ T393] rcu_torture_one_read (kernel/rcu/rcutorture.c:?) rcutorture 
[ 42.397219][ T393] ? __cfi_rcu_torture_reader (kernel/rcu/rcutorture.c:2426) rcutorture 
[ 42.397690][ T393] rcu_torture_reader (kernel/rcu/rcutorture.c:2443) rcutorture 
[ 42.398126][ T393] ? __cfi_rcu_torture_timer (kernel/rcu/rcutorture.c:2405) rcutorture 
[ 42.398565][ T393] kthread (kernel/kthread.c:465) 
[ 42.398857][ T393] ? __cfi_kthread (kernel/kthread.c:412) 
[ 42.399169][ T393] ret_from_fork (arch/x86/kernel/process.c:154) 
[ 42.399491][ T393] ? __cfi_kthread (kernel/kthread.c:412) 
[ 42.399815][ T393] ret_from_fork_asm (arch/x86/entry/entry_64.S:255) 
[   42.400151][  T393]  </TASK>


The kernel config and materials to reproduce are available at:
https://download.01.org/0day-ci/archive/20250826/202508261642.b15eefbb-lkp@intel.com



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