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Message-ID: <CAJnrk1bfZH=rJm3_7=0_JHN810akMTJsYkDsVs_fd1CSjjm3QQ@mail.gmail.com>
Date: Mon, 9 Feb 2026 08:56:11 -0800
From: Joanne Koong <joannelkoong@...il.com>
To: syzbot <syzbot+d38b792a5cbd941006fc@...kaller.appspotmail.com>
Cc: akpm@...ux-foundation.org, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
syzkaller-bugs@...glegroups.com, willy@...radead.org, Jan Kara <jack@...e.cz>
Subject: Re: [syzbot] [fs?] [mm?] possible deadlock in writeout_period
On Mon, Feb 9, 2026 at 6:37 AM syzbot
<syzbot+d38b792a5cbd941006fc@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 59e4d31a0470 Merge branches 'for-next/core' and 'for-next/..
> git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
> console output: https://syzkaller.appspot.com/x/log.txt?x=14454b22580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=8a8594efdc14f07a
> dashboard link: https://syzkaller.appspot.com/bug?extid=d38b792a5cbd941006fc
> compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
> userspace arch: arm64
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/746a1d5c4188/disk-59e4d31a.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/2eefade79f10/vmlinux-59e4d31a.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/140624ef24ed/Image-59e4d31a.gz.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+d38b792a5cbd941006fc@...kaller.appspotmail.com
>
> ========================================================
> WARNING: possible irq lock inversion dependency detected
> syzkaller #0 Not tainted
> --------------------------------------------------------
> syz-executor/6572 just changed the state of lock:
> ffff800097626150 (&p->sequence){+.-.}-{0:0}, at: writeout_period+0x94/0x11c mm/page-writeback.c:615
> but this lock was taken by another, HARDIRQ-safe lock in the past:
> (&xa->xa_lock#10){-.-.}-{3:3}
>
>
> and interrupts could create inverse lock ordering between them.
>
>
> other info that might help us debug this:
> Possible interrupt unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> lock(&p->sequence);
> local_irq_disable();
> lock(&xa->xa_lock#10);
> lock(&p->sequence);
> <Interrupt>
> lock(&xa->xa_lock#10);
>
> *** DEADLOCK ***
>
> 1 lock held by syz-executor/6572:
> #0: ffff800097bd7c40 ((&dom->period_timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:41 [inline]
> #0: ffff800097bd7c40 ((&dom->period_timer)){+.-.}-{0:0}, at: call_timer_fn+0xd4/0x814 kernel/time/timer.c:1738
>
> the shortest dependencies between 2nd lock and 1st lock:
> -> (&xa->xa_lock#10){-.-.}-{3:3} {
> IN-HARDIRQ-W at:
> lock_acquire+0x140/0x2e0 kernel/locking/lockdep.c:5868
> __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
> _raw_spin_lock_irqsave+0x5c/0x7c kernel/locking/spinlock.c:162
> __folio_end_writeback+0x10c/0x6f8 mm/page-writeback.c:2990
> folio_end_writeback_no_dropbehind+0xd0/0x204 mm/filemap.c:1661
> folio_end_writeback+0xd8/0x248 mm/filemap.c:1687
> end_buffer_async_write+0x20c/0x350 fs/buffer.c:419
> end_bio_bh_io_sync+0xb0/0x184 fs/buffer.c:2776
> bio_endio+0x8d4/0x910 block/bio.c:1675
> blk_complete_request block/blk-mq.c:908 [inline]
> blk_mq_end_request_batch+0x49c/0x105c block/blk-mq.c:1202
> nvme_complete_batch drivers/nvme/host/nvme.h:802 [inline]
> nvme_pci_complete_batch drivers/nvme/host/pci.c:1348 [inline]
> nvme_irq+0x1ec/0x240 drivers/nvme/host/pci.c:1450
> __handle_irq_event_percpu+0x20c/0x8e4 kernel/irq/handle.c:211
> handle_irq_event_percpu kernel/irq/handle.c:248 [inline]
> handle_irq_event+0x9c/0x1d0 kernel/irq/handle.c:265
> handle_fasteoi_irq+0x328/0x8d8 kernel/irq/chip.c:764
> generic_handle_irq_desc include/linux/irqdesc.h:172 [inline]
> handle_irq_desc kernel/irq/irqdesc.c:669 [inline]
> generic_handle_domain_irq+0xe0/0x140 kernel/irq/irqdesc.c:725
> __gic_handle_irq drivers/irqchip/irq-gic-v3.c:825 [inline]
> __gic_handle_irq_from_irqson drivers/irqchip/irq-gic-v3.c:876 [inline]
> gic_handle_irq+0x6c/0x18c drivers/irqchip/irq-gic-v3.c:920
> call_on_irq_stack+0x30/0x48 arch/arm64/kernel/entry.S:891
> do_interrupt_handler+0xd4/0x138 arch/arm64/kernel/entry-common.c:135
> __el1_irq arch/arm64/kernel/entry-common.c:497 [inline]
> el1_interrupt+0x3c/0x60 arch/arm64/kernel/entry-common.c:510
> el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:515
> el1h_64_irq+0x6c/0x70 arch/arm64/kernel/entry.S:592
> __daif_local_irq_restore arch/arm64/include/asm/irqflags.h:175 [inline]
> arch_local_irq_restore arch/arm64/include/asm/irqflags.h:195 [inline]
> kasan_quarantine_put+0xbc/0x1c8 mm/kasan/quarantine.c:234
> __kasan_slab_free+0x8c/0xa4 mm/kasan/common.c:295
> kasan_slab_free include/linux/kasan.h:235 [inline]
> slab_free_hook mm/slub.c:2540 [inline]
> slab_free_after_rcu_debug+0x120/0x2f8 mm/slub.c:6729
> rcu_do_batch kernel/rcu/tree.c:2605 [inline]
> rcu_core+0x848/0x1774 kernel/rcu/tree.c:2857
> rcu_core_si+0x10/0x1c kernel/rcu/tree.c:2874
> handle_softirqs+0x31c/0xc88 kernel/softirq.c:622
> run_ksoftirqd+0x70/0xc0 kernel/softirq.c:1063
> smpboot_thread_fn+0x4d8/0x9cc kernel/smpboot.c:160
> kthread+0x5fc/0x75c kernel/kthread.c:463
> ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844
> IN-SOFTIRQ-W at:
> lock_acquire+0x140/0x2e0 kernel/locking/lockdep.c:5868
> __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
> _raw_spin_lock_irqsave+0x5c/0x7c kernel/locking/spinlock.c:162
> __folio_end_writeback+0x10c/0x6f8 mm/page-writeback.c:2990
> folio_end_writeback_no_dropbehind+0xd0/0x204 mm/filemap.c:1661
> folio_end_writeback+0xd8/0x248 mm/filemap.c:1687
> end_buffer_async_write+0x20c/0x350 fs/buffer.c:419
> end_bio_bh_io_sync+0xb0/0x184 fs/buffer.c:2776
> bio_endio+0x8d4/0x910 block/bio.c:1675
> blk_complete_request block/blk-mq.c:908 [inline]
> blk_mq_end_request_batch+0x49c/0x105c block/blk-mq.c:1202
> nvme_complete_batch drivers/nvme/host/nvme.h:802 [inline]
> nvme_pci_complete_batch drivers/nvme/host/pci.c:1348 [inline]
> nvme_irq+0x1ec/0x240 drivers/nvme/host/pci.c:1450
> __handle_irq_event_percpu+0x20c/0x8e4 kernel/irq/handle.c:211
> handle_irq_event_percpu kernel/irq/handle.c:248 [inline]
> handle_irq_event+0x9c/0x1d0 kernel/irq/handle.c:265
> handle_fasteoi_irq+0x328/0x8d8 kernel/irq/chip.c:764
> generic_handle_irq_desc include/linux/irqdesc.h:172 [inline]
> handle_irq_desc kernel/irq/irqdesc.c:669 [inline]
> generic_handle_domain_irq+0xe0/0x140 kernel/irq/irqdesc.c:725
> __gic_handle_irq drivers/irqchip/irq-gic-v3.c:825 [inline]
> __gic_handle_irq_from_irqson drivers/irqchip/irq-gic-v3.c:876 [inline]
> gic_handle_irq+0x6c/0x18c drivers/irqchip/irq-gic-v3.c:920
> call_on_irq_stack+0x30/0x48 arch/arm64/kernel/entry.S:891
> do_interrupt_handler+0xd4/0x138 arch/arm64/kernel/entry-common.c:135
> __el1_irq arch/arm64/kernel/entry-common.c:497 [inline]
> el1_interrupt+0x3c/0x60 arch/arm64/kernel/entry-common.c:510
> el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:515
> el1h_64_irq+0x6c/0x70 arch/arm64/kernel/entry.S:592
> __daif_local_irq_restore arch/arm64/include/asm/irqflags.h:175 [inline]
> arch_local_irq_restore arch/arm64/include/asm/irqflags.h:195 [inline]
> kasan_quarantine_put+0xbc/0x1c8 mm/kasan/quarantine.c:234
> __kasan_slab_free+0x8c/0xa4 mm/kasan/common.c:295
> kasan_slab_free include/linux/kasan.h:235 [inline]
> slab_free_hook mm/slub.c:2540 [inline]
> slab_free_after_rcu_debug+0x120/0x2f8 mm/slub.c:6729
> rcu_do_batch kernel/rcu/tree.c:2605 [inline]
> rcu_core+0x848/0x1774 kernel/rcu/tree.c:2857
> rcu_core_si+0x10/0x1c kernel/rcu/tree.c:2874
> handle_softirqs+0x31c/0xc88 kernel/softirq.c:622
> run_ksoftirqd+0x70/0xc0 kernel/softirq.c:1063
> smpboot_thread_fn+0x4d8/0x9cc kernel/smpboot.c:160
> kthread+0x5fc/0x75c kernel/kthread.c:463
> ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844
> INITIAL USE at:
> lock_acquire+0x140/0x2e0 kernel/locking/lockdep.c:5868
> __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
> _raw_spin_lock_irq+0x58/0x70 kernel/locking/spinlock.c:170
> spin_lock_irq include/linux/spinlock.h:376 [inline]
> shmem_add_to_page_cache+0x564/0xa24 mm/shmem.c:904
> shmem_alloc_and_add_folio+0x758/0x10c4 mm/shmem.c:1958
> shmem_get_folio_gfp+0x4d4/0x159c mm/shmem.c:2556
> shmem_read_folio_gfp+0x8c/0xf0 mm/shmem.c:5970
> drm_gem_get_pages+0x1cc/0x7c0 drivers/gpu/drm/drm_gem.c:654
> drm_gem_shmem_get_pages_locked+0x1d4/0x364 drivers/gpu/drm/drm_gem_shmem_helper.c:240
> drm_gem_shmem_pin_locked+0x1f8/0x410 drivers/gpu/drm/drm_gem_shmem_helper.c:301
> drm_gem_shmem_vmap_locked+0x3cc/0x658 drivers/gpu/drm/drm_gem_shmem_helper.c:405
> drm_gem_shmem_object_vmap+0x28/0x38 include/drm/drm_gem_shmem_helper.h:245
> drm_gem_vmap_locked drivers/gpu/drm/drm_gem.c:1273 [inline]
> drm_gem_vmap+0x104/0x1d8 drivers/gpu/drm/drm_gem.c:1315
> drm_client_buffer_vmap+0x68/0xb0 drivers/gpu/drm/drm_client.c:355
> drm_fbdev_shmem_driver_fbdev_probe+0x1f4/0x700 drivers/gpu/drm/drm_fbdev_shmem.c:159
> drm_fb_helper_single_fb_probe drivers/gpu/drm/drm_fb_helper.c:1562 [inline]
> __drm_fb_helper_initial_config_and_unlock+0x108c/0x1728 drivers/gpu/drm/drm_fb_helper.c:1741
> drm_fb_helper_initial_config+0x3c/0x58 drivers/gpu/drm/drm_fb_helper.c:1828
> drm_fbdev_client_hotplug+0x154/0x22c drivers/gpu/drm/clients/drm_fbdev_client.c:66
> drm_client_register+0x13c/0x1d4 drivers/gpu/drm/drm_client.c:143
> drm_fbdev_client_setup+0x194/0x3d0 drivers/gpu/drm/clients/drm_fbdev_client.c:168
> drm_client_setup+0x114/0x228 drivers/gpu/drm/clients/drm_client_setup.c:46
> vkms_create+0x370/0x420 drivers/gpu/drm/vkms/vkms_drv.c:211
> vkms_init+0x64/0x9c drivers/gpu/drm/vkms/vkms_drv.c:239
> do_one_initcall+0x248/0x9b4 init/main.c:1378
> do_initcall_level+0x128/0x1c4 init/main.c:1440
> do_initcalls+0x70/0xd0 init/main.c:1456
> do_basic_setup+0x78/0x8c init/main.c:1475
> kernel_init_freeable+0x268/0x39c init/main.c:1688
> kernel_init+0x24/0x1dc init/main.c:1578
> ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844
> }
> ... key at: [<ffff80009764a620>] xa_init_flags.__key+0x0/0x20
> ... acquired at:
> seqcount_lockdep_reader_access include/linux/seqlock.h:72 [inline]
> fprop_fraction_percpu+0xf0/0x270 lib/flex_proportions.c:155
> __fprop_add_percpu_max+0x130/0x1f4 lib/flex_proportions.c:186
> wb_domain_writeout_add mm/page-writeback.c:562 [inline]
> __wb_writeout_add+0xbc/0x27c mm/page-writeback.c:586
> __folio_end_writeback+0x380/0x6f8 mm/page-writeback.c:2997
> folio_end_writeback_no_dropbehind+0xd0/0x204 mm/filemap.c:1661
> folio_end_writeback+0xd8/0x248 mm/filemap.c:1687
> iomap_finish_folio_write+0x1c0/0x2a4 fs/iomap/buffered-io.c:1713
> fuse_writepage_finish fs/fuse/file.c:1903 [inline]
> fuse_writepage_end+0x238/0x454 fs/fuse/file.c:2003
> fuse_request_end+0x898/0xc10 fs/fuse/dev.c:507
> fuse_dev_end_requests fs/fuse/dev.c:2415 [inline]
> fuse_abort_conn+0xe88/0x10a0 fs/fuse/dev.c:2513
> fuse_dev_release+0x430/0x4c8 fs/fuse/dev.c:2556
> __fput+0x340/0x75c fs/file_table.c:468
> fput_close_sync+0x100/0x264 fs/file_table.c:573
> __do_sys_close fs/open.c:1573 [inline]
> __se_sys_close fs/open.c:1558 [inline]
> __arm64_sys_close+0x7c/0x118 fs/open.c:1558
> __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
> invoke_syscall+0x98/0x254 arch/arm64/kernel/syscall.c:49
> el0_svc_common+0xe8/0x23c arch/arm64/kernel/syscall.c:132
> do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
> el0_svc+0x5c/0x26c arch/arm64/kernel/entry-common.c:724
> el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:743
> el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596
>
> -> (&p->sequence){+.-.}-{0:0} {
> HARDIRQ-ON-W at:
> lock_acquire+0x140/0x2e0 kernel/locking/lockdep.c:5868
> do_write_seqcount_begin_nested include/linux/seqlock.h:477 [inline]
> do_write_seqcount_begin include/linux/seqlock.h:503 [inline]
> fprop_new_period+0x3b8/0x718 lib/flex_proportions.c:74
> writeout_period+0x94/0x11c mm/page-writeback.c:615
> call_timer_fn+0x19c/0x814 kernel/time/timer.c:1748
> expire_timers kernel/time/timer.c:1799 [inline]
> __run_timers kernel/time/timer.c:2373 [inline]
> __run_timer_base+0x51c/0x76c kernel/time/timer.c:2385
> run_timer_base kernel/time/timer.c:2394 [inline]
> run_timer_softirq+0x11c/0x194 kernel/time/timer.c:2405
> handle_softirqs+0x31c/0xc88 kernel/softirq.c:622
> __do_softirq+0x14/0x20 kernel/softirq.c:656
> ____do_softirq+0x14/0x20 arch/arm64/kernel/irq.c:68
> call_on_irq_stack+0x30/0x48 arch/arm64/kernel/entry.S:891
> do_softirq_own_stack+0x20/0x2c arch/arm64/kernel/irq.c:73
> invoke_softirq kernel/softirq.c:503 [inline]
> __irq_exit_rcu+0x1b0/0x478 kernel/softirq.c:723
> irq_exit_rcu+0x14/0x84 kernel/softirq.c:739
> __el1_irq arch/arm64/kernel/entry-common.c:498 [inline]
> el1_interrupt+0x40/0x60 arch/arm64/kernel/entry-common.c:510
> el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:515
> el1h_64_irq+0x6c/0x70 arch/arm64/kernel/entry.S:592
> __daif_local_irq_enable arch/arm64/include/asm/irqflags.h:26 [inline]
> arch_local_irq_enable arch/arm64/include/asm/irqflags.h:48 [inline]
> preempt_schedule_irq+0x78/0x188 kernel/sched/core.c:7189
> raw_irqentry_exit_cond_resched+0x30/0x44 kernel/entry/common.c:173
> irqentry_exit+0x1b0/0x308 kernel/entry/common.c:216
> exit_to_kernel_mode+0x10/0x1c arch/arm64/kernel/entry-common.c:58
> __el1_irq arch/arm64/kernel/entry-common.c:500 [inline]
> el1_interrupt+0x4c/0x60 arch/arm64/kernel/entry-common.c:510
> el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:515
> el1h_64_irq+0x6c/0x70 arch/arm64/kernel/entry.S:592
> __daif_local_irq_restore arch/arm64/include/asm/irqflags.h:175 [inline]
> arch_local_irq_restore arch/arm64/include/asm/irqflags.h:195 [inline]
> class_irqsave_destructor include/linux/irqflags.h:266 [inline]
> __free_object+0x514/0x720 lib/debugobjects.c:524
> free_object lib/debugobjects.c:532 [inline]
> debug_object_free+0x298/0x3e4 lib/debugobjects.c:976
> destroy_hrtimer_on_stack kernel/time/hrtimer.c:448 [inline]
> hrtimer_nanosleep+0x214/0x2a4 kernel/time/hrtimer.c:2178
> common_nsleep+0xa0/0xb8 kernel/time/posix-timers.c:1352
> __do_sys_clock_nanosleep kernel/time/posix-timers.c:1398 [inline]
> __se_sys_clock_nanosleep kernel/time/posix-timers.c:1375 [inline]
> __arm64_sys_clock_nanosleep+0x334/0x370 kernel/time/posix-timers.c:1375
> __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
> invoke_syscall+0x98/0x254 arch/arm64/kernel/syscall.c:49
> el0_svc_common+0xe8/0x23c arch/arm64/kernel/syscall.c:132
> do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
> el0_svc+0x5c/0x26c arch/arm64/kernel/entry-common.c:724
> el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:743
> el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596
> IN-SOFTIRQ-W at:
> lock_acquire+0x140/0x2e0 kernel/locking/lockdep.c:5868
> do_write_seqcount_begin_nested include/linux/seqlock.h:477 [inline]
> do_write_seqcount_begin include/linux/seqlock.h:503 [inline]
> fprop_new_period+0x3b8/0x718 lib/flex_proportions.c:74
> writeout_period+0x94/0x11c mm/page-writeback.c:615
> call_timer_fn+0x19c/0x814 kernel/time/timer.c:1748
> expire_timers kernel/time/timer.c:1799 [inline]
> __run_timers kernel/time/timer.c:2373 [inline]
> __run_timer_base+0x51c/0x76c kernel/time/timer.c:2385
> run_timer_base kernel/time/timer.c:2394 [inline]
> run_timer_softirq+0x11c/0x194 kernel/time/timer.c:2405
> handle_softirqs+0x31c/0xc88 kernel/softirq.c:622
> __do_softirq+0x14/0x20 kernel/softirq.c:656
> ____do_softirq+0x14/0x20 arch/arm64/kernel/irq.c:68
> call_on_irq_stack+0x30/0x48 arch/arm64/kernel/entry.S:891
> do_softirq_own_stack+0x20/0x2c arch/arm64/kernel/irq.c:73
> invoke_softirq kernel/softirq.c:503 [inline]
> __irq_exit_rcu+0x1b0/0x478 kernel/softirq.c:723
> irq_exit_rcu+0x14/0x84 kernel/softirq.c:739
> __el1_irq arch/arm64/kernel/entry-common.c:498 [inline]
> el1_interrupt+0x40/0x60 arch/arm64/kernel/entry-common.c:510
> el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:515
> el1h_64_irq+0x6c/0x70 arch/arm64/kernel/entry.S:592
> __daif_local_irq_enable arch/arm64/include/asm/irqflags.h:26 [inline]
> arch_local_irq_enable arch/arm64/include/asm/irqflags.h:48 [inline]
> preempt_schedule_irq+0x78/0x188 kernel/sched/core.c:7189
> raw_irqentry_exit_cond_resched+0x30/0x44 kernel/entry/common.c:173
> irqentry_exit+0x1b0/0x308 kernel/entry/common.c:216
> exit_to_kernel_mode+0x10/0x1c arch/arm64/kernel/entry-common.c:58
> __el1_irq arch/arm64/kernel/entry-common.c:500 [inline]
> el1_interrupt+0x4c/0x60 arch/arm64/kernel/entry-common.c:510
> el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:515
> el1h_64_irq+0x6c/0x70 arch/arm64/kernel/entry.S:592
> __daif_local_irq_restore arch/arm64/include/asm/irqflags.h:175 [inline]
> arch_local_irq_restore arch/arm64/include/asm/irqflags.h:195 [inline]
> class_irqsave_destructor include/linux/irqflags.h:266 [inline]
> __free_object+0x514/0x720 lib/debugobjects.c:524
> free_object lib/debugobjects.c:532 [inline]
> debug_object_free+0x298/0x3e4 lib/debugobjects.c:976
> destroy_hrtimer_on_stack kernel/time/hrtimer.c:448 [inline]
> hrtimer_nanosleep+0x214/0x2a4 kernel/time/hrtimer.c:2178
> common_nsleep+0xa0/0xb8 kernel/time/posix-timers.c:1352
> __do_sys_clock_nanosleep kernel/time/posix-timers.c:1398 [inline]
> __se_sys_clock_nanosleep kernel/time/posix-timers.c:1375 [inline]
> __arm64_sys_clock_nanosleep+0x334/0x370 kernel/time/posix-timers.c:1375
> __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
> invoke_syscall+0x98/0x254 arch/arm64/kernel/syscall.c:49
> el0_svc_common+0xe8/0x23c arch/arm64/kernel/syscall.c:132
> do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
> el0_svc+0x5c/0x26c arch/arm64/kernel/entry-common.c:724
> el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:743
> el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596
> INITIAL READ USE at:
> lock_acquire+0x140/0x2e0 kernel/locking/lockdep.c:5868
> seqcount_lockdep_reader_access include/linux/seqlock.h:72 [inline]
> fprop_fraction_percpu+0xac/0x270 lib/flex_proportions.c:155
> __wb_calc_thresh+0xfc/0x3b0 mm/page-writeback.c:913
> wb_bg_dirty_limits mm/page-writeback.c:2130 [inline]
> domain_over_bg_thresh+0xb8/0x1f0 mm/page-writeback.c:2144
> wb_over_bg_thresh+0xf8/0x17c mm/page-writeback.c:2165
> wb_check_background_flush fs/fs-writeback.c:2278 [inline]
> wb_do_writeback fs/fs-writeback.c:2376 [inline]
> wb_workfn+0xa30/0xdc0 fs/fs-writeback.c:2403
> process_one_work+0x7c0/0x1558 kernel/workqueue.c:3257
> process_scheduled_works kernel/workqueue.c:3340 [inline]
> worker_thread+0x958/0xed8 kernel/workqueue.c:3421
> kthread+0x5fc/0x75c kernel/kthread.c:463
> ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844
> }
> ... key at: [<ffff800097b9a340>] fprop_global_init.__key.1+0x0/0x20
> ... acquired at:
> mark_lock+0x170/0x1d0 kernel/locking/lockdep.c:4753
> mark_usage kernel/locking/lockdep.c:4662 [inline]
> __lock_acquire+0x9a0/0x30a4 kernel/locking/lockdep.c:5191
> lock_acquire+0x140/0x2e0 kernel/locking/lockdep.c:5868
> do_write_seqcount_begin_nested include/linux/seqlock.h:477 [inline]
> do_write_seqcount_begin include/linux/seqlock.h:503 [inline]
> fprop_new_period+0x3b8/0x718 lib/flex_proportions.c:74
> writeout_period+0x94/0x11c mm/page-writeback.c:615
> call_timer_fn+0x19c/0x814 kernel/time/timer.c:1748
> expire_timers kernel/time/timer.c:1799 [inline]
> __run_timers kernel/time/timer.c:2373 [inline]
> __run_timer_base+0x51c/0x76c kernel/time/timer.c:2385
> run_timer_base kernel/time/timer.c:2394 [inline]
> run_timer_softirq+0x11c/0x194 kernel/time/timer.c:2405
> handle_softirqs+0x31c/0xc88 kernel/softirq.c:622
> __do_softirq+0x14/0x20 kernel/softirq.c:656
> ____do_softirq+0x14/0x20 arch/arm64/kernel/irq.c:68
> call_on_irq_stack+0x30/0x48 arch/arm64/kernel/entry.S:891
> do_softirq_own_stack+0x20/0x2c arch/arm64/kernel/irq.c:73
> invoke_softirq kernel/softirq.c:503 [inline]
> __irq_exit_rcu+0x1b0/0x478 kernel/softirq.c:723
> irq_exit_rcu+0x14/0x84 kernel/softirq.c:739
> __el1_irq arch/arm64/kernel/entry-common.c:498 [inline]
> el1_interrupt+0x40/0x60 arch/arm64/kernel/entry-common.c:510
> el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:515
> el1h_64_irq+0x6c/0x70 arch/arm64/kernel/entry.S:592
> __daif_local_irq_enable arch/arm64/include/asm/irqflags.h:26 [inline]
> arch_local_irq_enable arch/arm64/include/asm/irqflags.h:48 [inline]
> preempt_schedule_irq+0x78/0x188 kernel/sched/core.c:7189
> raw_irqentry_exit_cond_resched+0x30/0x44 kernel/entry/common.c:173
> irqentry_exit+0x1b0/0x308 kernel/entry/common.c:216
> exit_to_kernel_mode+0x10/0x1c arch/arm64/kernel/entry-common.c:58
> __el1_irq arch/arm64/kernel/entry-common.c:500 [inline]
> el1_interrupt+0x4c/0x60 arch/arm64/kernel/entry-common.c:510
> el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:515
> el1h_64_irq+0x6c/0x70 arch/arm64/kernel/entry.S:592
> __daif_local_irq_restore arch/arm64/include/asm/irqflags.h:175 [inline]
> arch_local_irq_restore arch/arm64/include/asm/irqflags.h:195 [inline]
> class_irqsave_destructor include/linux/irqflags.h:266 [inline]
> __free_object+0x514/0x720 lib/debugobjects.c:524
> free_object lib/debugobjects.c:532 [inline]
> debug_object_free+0x298/0x3e4 lib/debugobjects.c:976
> destroy_hrtimer_on_stack kernel/time/hrtimer.c:448 [inline]
> hrtimer_nanosleep+0x214/0x2a4 kernel/time/hrtimer.c:2178
> common_nsleep+0xa0/0xb8 kernel/time/posix-timers.c:1352
> __do_sys_clock_nanosleep kernel/time/posix-timers.c:1398 [inline]
> __se_sys_clock_nanosleep kernel/time/posix-timers.c:1375 [inline]
> __arm64_sys_clock_nanosleep+0x334/0x370 kernel/time/posix-timers.c:1375
> __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
> invoke_syscall+0x98/0x254 arch/arm64/kernel/syscall.c:49
> el0_svc_common+0xe8/0x23c arch/arm64/kernel/syscall.c:132
> do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
> el0_svc+0x5c/0x26c arch/arm64/kernel/entry-common.c:724
> el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:743
> el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596
>
>
> stack backtrace:
> CPU: 1 UID: 0 PID: 6572 Comm: syz-executor Not tainted syzkaller #0 PREEMPT
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/03/2025
> Call trace:
> show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C)
> __dump_stack+0x30/0x40 lib/dump_stack.c:94
> dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120
> dump_stack+0x1c/0x28 lib/dump_stack.c:129
> print_irq_inversion_bug+0x1f8/0x1fc kernel/locking/lockdep.c:4125
> mark_lock_irq+0x3b4/0x47c kernel/locking/lockdep.c:-1
> mark_lock+0x170/0x1d0 kernel/locking/lockdep.c:4753
> mark_usage kernel/locking/lockdep.c:4662 [inline]
> __lock_acquire+0x9a0/0x30a4 kernel/locking/lockdep.c:5191
> lock_acquire+0x140/0x2e0 kernel/locking/lockdep.c:5868
> do_write_seqcount_begin_nested include/linux/seqlock.h:477 [inline]
> do_write_seqcount_begin include/linux/seqlock.h:503 [inline]
> fprop_new_period+0x3b8/0x718 lib/flex_proportions.c:74
> writeout_period+0x94/0x11c mm/page-writeback.c:615
> call_timer_fn+0x19c/0x814 kernel/time/timer.c:1748
> expire_timers kernel/time/timer.c:1799 [inline]
> __run_timers kernel/time/timer.c:2373 [inline]
> __run_timer_base+0x51c/0x76c kernel/time/timer.c:2385
> run_timer_base kernel/time/timer.c:2394 [inline]
> run_timer_softirq+0x11c/0x194 kernel/time/timer.c:2405
> handle_softirqs+0x31c/0xc88 kernel/softirq.c:622
> __do_softirq+0x14/0x20 kernel/softirq.c:656
> ____do_softirq+0x14/0x20 arch/arm64/kernel/irq.c:68
> call_on_irq_stack+0x30/0x48 arch/arm64/kernel/entry.S:891
> do_softirq_own_stack+0x20/0x2c arch/arm64/kernel/irq.c:73
> invoke_softirq kernel/softirq.c:503 [inline]
> __irq_exit_rcu+0x1b0/0x478 kernel/softirq.c:723
> irq_exit_rcu+0x14/0x84 kernel/softirq.c:739
> __el1_irq arch/arm64/kernel/entry-common.c:498 [inline]
> el1_interrupt+0x40/0x60 arch/arm64/kernel/entry-common.c:510
> el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:515
> el1h_64_irq+0x6c/0x70 arch/arm64/kernel/entry.S:592
> __daif_local_irq_enable arch/arm64/include/asm/irqflags.h:26 [inline] (P)
> arch_local_irq_enable arch/arm64/include/asm/irqflags.h:48 [inline] (P)
> preempt_schedule_irq+0x78/0x188 kernel/sched/core.c:7189 (P)
> raw_irqentry_exit_cond_resched+0x30/0x44 kernel/entry/common.c:173
> irqentry_exit+0x1b0/0x308 kernel/entry/common.c:216
> exit_to_kernel_mode+0x10/0x1c arch/arm64/kernel/entry-common.c:58
> __el1_irq arch/arm64/kernel/entry-common.c:500 [inline]
> el1_interrupt+0x4c/0x60 arch/arm64/kernel/entry-common.c:510
> el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:515
> el1h_64_irq+0x6c/0x70 arch/arm64/kernel/entry.S:592
> __daif_local_irq_restore arch/arm64/include/asm/irqflags.h:175 [inline] (P)
> arch_local_irq_restore arch/arm64/include/asm/irqflags.h:195 [inline] (P)
> class_irqsave_destructor include/linux/irqflags.h:266 [inline] (P)
> __free_object+0x514/0x720 lib/debugobjects.c:524 (P)
> free_object lib/debugobjects.c:532 [inline]
> debug_object_free+0x298/0x3e4 lib/debugobjects.c:976
> destroy_hrtimer_on_stack kernel/time/hrtimer.c:448 [inline]
> hrtimer_nanosleep+0x214/0x2a4 kernel/time/hrtimer.c:2178
> common_nsleep+0xa0/0xb8 kernel/time/posix-timers.c:1352
> __do_sys_clock_nanosleep kernel/time/posix-timers.c:1398 [inline]
> __se_sys_clock_nanosleep kernel/time/posix-timers.c:1375 [inline]
> __arm64_sys_clock_nanosleep+0x334/0x370 kernel/time/posix-timers.c:1375
> __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
> invoke_syscall+0x98/0x254 arch/arm64/kernel/syscall.c:49
> el0_svc_common+0xe8/0x23c arch/arm64/kernel/syscall.c:132
> do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
> el0_svc+0x5c/0x26c arch/arm64/kernel/entry-common.c:724
> el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:743
> el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
#syz fix: flex_proportions: make fprop_new_period() hardirq safe
This was fixed by Jan a few weeks ago (commit dd9e2f5b38f1f in the
linux-next tree) [1]. I think Jan's fix just hasn't been
pulled into the arm64 tree yet [2].
Thanks,
Joanne
[1] https://lore.kernel.org/all/20260121112729.24463-2-jack@suse.cz/
[2] https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/log/?qt=author&q=Jan+Kara
>
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
>
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
>
> If you want to undo deduplication, reply with:
> #syz undup
>
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