Re: [RFC v2 1/1] fs/namespace: defer RCU sync for MNT_DETACH umount

From: kernel test robot
Date: Tue Apr 30 2024 - 10:27:26 EST



Hello,

kernel test robot noticed "WARNING:inconsistent_lock_state" on:

commit: 9a4131bb20fbeb5980c3e21709488b9c4ef2eee5 ("[RFC v2 1/1] fs/namespace: defer RCU sync for MNT_DETACH umount")
url: https://github.com/intel-lab-lkp/linux/commits/Lucas-Karpinski/fs-namespace-defer-RCU-sync-for-MNT_DETACH-umount/20240427-035724
base: https://git.kernel.org/cgit/linux/kernel/git/vfs/vfs.git vfs.all
patch link: https://lore.kernel.org/all/20240426195429.28547-2-lkarpins@xxxxxxxxxx/
patch subject: [RFC v2 1/1] fs/namespace: defer RCU sync for MNT_DETACH umount

in testcase: boot

compiler: gcc-7
test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G

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


+---------------------------------------------------+------------+------------+
| | eea3260250 | 9a4131bb20 |
+---------------------------------------------------+------------+------------+
| WARNING:inconsistent_lock_state | 0 | 12 |
| inconsistent{SOFTIRQ-ON-W}->{IN-SOFTIRQ-W}usage | 0 | 12 |
+---------------------------------------------------+------------+------------+


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/202404302220.f8959d4c-oliver.sang@xxxxxxxxx


[ 19.407878][ C0]
[ 19.408164][ C0] ================================
[ 19.408629][ C0] WARNING: inconsistent lock state
[ 19.409083][ C0] 6.9.0-rc3-00075-g9a4131bb20fb #2 Tainted: G W TN
[ 19.409757][ C0] --------------------------------
[ 19.410209][ C0] inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
[ 19.410777][ C0] ksoftirqd/0/10 [HC0[0]:SC1[3]:HE1:SE0] takes:
[ 19.411306][ C0] ffffffff83066cd0 (mount_lock){+.?.}-{2:2}, at: mntput_no_expire (include/linux/seqlock.h:469 include/linux/seqlock.h:495 include/linux/seqlock.h:823 fs/namespace.c:114 fs/namespace.c:1314)
[ 19.412072][ C0] {SOFTIRQ-ON-W} state was registered at:
[ 19.412574][ C0] lock_acquire (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:5756)
[ 19.412999][ C0] _raw_spin_lock (include/linux/spinlock_api_smp.h:134 kernel/locking/spinlock.c:154)
[ 19.413421][ C0] vfs_create_mount (include/linux/seqlock.h:469 include/linux/seqlock.h:495 include/linux/seqlock.h:823 fs/namespace.c:114 fs/namespace.c:1122)
[ 19.413862][ C0] fc_mount (fs/namespace.c:1134)
[ 19.414246][ C0] vfs_kern_mount (fs/namespace.c:1148 fs/namespace.c:1181)
[ 19.414713][ C0] kern_mount (fs/namespace.c:5248)
[ 19.415106][ C0] shmem_init (mm/shmem.c:4684)
[ 19.415508][ C0] mnt_init (fs/namespace.c:5232)
[ 19.415907][ C0] vfs_caches_init (fs/dcache.c:3187)
[ 19.416333][ C0] start_kernel (init/main.c:1058)
[ 19.416760][ C0] x86_64_start_reservations (arch/x86/kernel/head64.c:495)
[ 19.417245][ C0] x86_64_start_kernel (arch/x86/kernel/head64.c:488)
[ 19.417694][ C0] common_startup_64 (arch/x86/kernel/head_64.S:421)
[ 19.418133][ C0] irq event stamp: 868370
[ 19.418530][ C0] hardirqs last enabled at (868370): __local_bh_enable_ip (arch/x86/include/asm/paravirt.h:698 kernel/softirq.c:387)
[ 19.419370][ C0] hardirqs last disabled at (868369): __local_bh_enable_ip (kernel/softirq.c:364 (discriminator 1))
[ 19.420216][ C0] softirqs last enabled at (868292): __do_softirq (arch/x86/include/asm/preempt.h:26 kernel/softirq.c:401 kernel/softirq.c:583)
[ 19.421025][ C0] softirqs last disabled at (868297): run_ksoftirqd (kernel/softirq.c:411 kernel/softirq.c:925)
[ 19.421823][ C0]
[ 19.421823][ C0] other info that might help us debug this:
[ 19.422522][ C0] Possible unsafe locking scenario:
[ 19.422522][ C0]
[ 19.423184][ C0] CPU0
[ 19.423510][ C0] ----
[ 19.423838][ C0] lock(mount_lock);
[ 19.424225][ C0] <Interrupt>
[ 19.424567][ C0] lock(mount_lock);
[ 19.425115][ C0]
[ 19.425115][ C0] *** DEADLOCK ***
[ 19.425115][ C0]
[ 19.425858][ C0] 2 locks held by ksoftirqd/0/10:
[ 19.426297][ C0] #0: ffffffff8301d700 (rcu_callback){....}-{0:0}, at: rcu_process_callbacks (include/linux/bottom_half.h:20 kernel/rcu/tiny.c:133)
[ 19.427122][ C0] #1: ffffffff8301d7c0 (rcu_read_lock){....}-{1:2}, at: mntput_no_expire (include/linux/rcupdate.h:329 include/linux/rcupdate.h:781 fs/namespace.c:1299)
[ 19.427921][ C0]
[ 19.427921][ C0] stack backtrace:
[ 19.428459][ C0] CPU: 0 PID: 10 Comm: ksoftirqd/0 Tainted: G W TN 6.9.0-rc3-00075-g9a4131bb20fb #2
[ 19.429328][ C0] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
[ 19.430179][ C0] Call Trace:
[ 19.430505][ C0] <TASK>
[ 19.430805][ C0] dump_stack_lvl (arch/x86/include/asm/paravirt.h:687 (discriminator 3) arch/x86/include/asm/irqflags.h:127 (discriminator 3) lib/dump_stack.c:117 (discriminator 3))
[ 19.431221][ C0] mark_lock+0x473/0x4c0
[ 19.431661][ C0] ? __lock_acquire (kernel/locking/lockdep.c:4599 kernel/locking/lockdep.c:5091)
[ 19.432102][ C0] ? __lock_acquire (include/linux/hash.h:78 kernel/locking/lockdep.c:3759 kernel/locking/lockdep.c:3782 kernel/locking/lockdep.c:3837 kernel/locking/lockdep.c:5137)
[ 19.432550][ C0] ? __lock_acquire (kernel/locking/lockdep.c:4567 kernel/locking/lockdep.c:5091)
[ 19.432989][ C0] __lock_acquire (kernel/locking/lockdep.c:4567 kernel/locking/lockdep.c:5091)
[ 19.433415][ C0] ? __lock_acquire (kernel/locking/lockdep.c:5134 (discriminator 9))
[ 19.433856][ C0] lock_acquire (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:5756)
[ 19.434269][ C0] ? mntput_no_expire (include/linux/seqlock.h:469 include/linux/seqlock.h:495 include/linux/seqlock.h:823 fs/namespace.c:114 fs/namespace.c:1314)
[ 19.434708][ C0] ? mntput_no_expire (include/linux/rcupdate.h:329 include/linux/rcupdate.h:781 fs/namespace.c:1299)
[ 19.435144][ C0] _raw_spin_lock (include/linux/spinlock_api_smp.h:134 kernel/locking/spinlock.c:154)
[ 19.435555][ C0] ? mntput_no_expire (include/linux/seqlock.h:469 include/linux/seqlock.h:495 include/linux/seqlock.h:823 fs/namespace.c:114 fs/namespace.c:1314)
[ 19.435994][ C0] mntput_no_expire (include/linux/seqlock.h:469 include/linux/seqlock.h:495 include/linux/seqlock.h:823 fs/namespace.c:114 fs/namespace.c:1314)
[ 19.436421][ C0] ? rcu_process_callbacks (include/linux/bottom_half.h:20 kernel/rcu/tiny.c:133)
[ 19.436900][ C0] free_mounts (fs/namespace.c:1571)
[ 19.437291][ C0] ? __x64_sys_mount_setattr (fs/namespace.c:1574)
[ 19.437772][ C0] ? __x64_sys_mount_setattr (fs/namespace.c:1574)
[ 19.438253][ C0] delayed_mount_release (fs/namespace.c:1579)
[ 19.438699][ C0] rcu_process_callbacks (include/linux/rcupdate.h:339 kernel/rcu/tiny.c:103 kernel/rcu/tiny.c:134)
[ 19.439151][ C0] __do_softirq (arch/x86/include/asm/atomic.h:23 include/linux/atomic/atomic-arch-fallback.h:457 include/linux/jump_label.h:260 include/linux/jump_label.h:270 include/trace/events/irq.h:142 kernel/softirq.c:555)
[ 19.439556][ C0] ? smpboot_thread_fn (kernel/smpboot.c:112)
[ 19.439997][ C0] ? sort_range (kernel/smpboot.c:107)
[ 19.440389][ C0] run_ksoftirqd (kernel/softirq.c:411 kernel/softirq.c:925)
[ 19.443032][ C0] smpboot_thread_fn (kernel/smpboot.c:164 (discriminator 3))
[ 19.443510][ C0] kthread (kernel/kthread.c:388)
[ 19.443887][ C0] ? kthread_complete_and_exit (kernel/kthread.c:341)
[ 19.444367][ C0] ret_from_fork (arch/x86/kernel/process.c:153)
[ 19.444788][ C0] ? kthread_complete_and_exit (kernel/kthread.c:341)
[ 19.445269][ C0] ret_from_fork_asm (arch/x86/entry/entry_64.S:253)
[ 19.445696][ C0] </TASK>


The kernel config and materials to reproduce are available at:
https://download.01.org/0day-ci/archive/20240430/202404302220.f8959d4c-oliver.sang@xxxxxxxxx



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