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INFO: rcu detected stall in ext4_end_io_rsv_work (3)

Status: upstream: reported C repro on 2025/05/12 09:11
Subsystems: ext4 mm
Labels: prio:normal
[Documentation on labels]
Reported-by: syzbot+bb842a51b5abbae5a245@syzkaller.appspotmail.com
First crash: 427d, last: 156d
Cause bisection: failed (error log, bisect log)
  
Fix bisection: failed (error log, bisect log)
  
▶ ▼ ✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
3dc067f1-93cb-451b-8c9a-0cea923d351e assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ INFO: rcu detected stall in ext4_end_io_rsv_work (3) 2026/05/21 19:30 2026/05/21 19:30 2026/05/21 20:26 d57425845dbe663f86e1e54a4997e95bd557b624
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [mm?] [ext4?] INFO: rcu detected stall in ext4_end_io_rsv_work (3) 0 (1) 2025/05/12 09:11
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 INFO: rcu detected stall in ext4_end_io_rsv_work origin:lts-only 1 C inconclusive 2 183d 260d 0/3 upstream: reported C repro on 2025/09/22 08:45
upstream INFO: rcu detected stall in ext4_end_io_rsv_work (2) mm 1 1 663d 663d 0/29 auto-obsoleted due to no activity on 2024/11/13 20:18
upstream INFO: rcu detected stall in ext4_end_io_rsv_work ext4 1 1 2077d 2077d 0/29 auto-closed as invalid on 2020/12/30 15:48
▶ ▼ Last patch testing requests (2)
Created Duration User Patch Repo Result
2026/04/15 18:12 28m retest repro upstream report log
2025/05/22 10:03 23m retest repro upstream report log
▶ ▼ Fix bisection attempts (7)
Created Duration User Patch Repo Result
2026/02/03 16:24 22m bisect fix upstream error job log
2026/01/04 05:48 4h07m bisect fix upstream OK (0) job log log
2025/11/02 06:41 2h58m bisect fix upstream OK (0) job log log
2025/09/26 04:41 3h49m bisect fix upstream OK (0) job log log
2025/08/22 20:57 5h25m bisect fix upstream OK (0) job log log
2025/07/17 11:47 6h20m bisect fix upstream OK (0) job log log
2025/06/07 09:18 3h58m bisect fix upstream OK (0) job log log

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (3 ticks this GP) idle=1d3c/1/0x4000000000000000 softirq=14732/14732 fqs=0
rcu: 	(detected by 1, t=10502 jiffies, g=6677, q=10638 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 3557 Comm: kworker/u8:8 Not tainted 6.15.0-rc5-syzkaller-00038-g707df3375124 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/29/2025
Workqueue: ext4-rsv-conversion ext4_end_io_rsv_work
RIP: 0010:__kasan_check_write+0x8/0x20 mm/kasan/shadow.c:37
Code: f0 ff ff 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 48 8b 0c 24 <89> f6 ba 01 00 00 00 e9 4c f0 ff ff 66 66 2e 0f 1f 84 00 00 00 00
RSP: 0018:ffffc90000007da0 EFLAGS: 00000086
RAX: 0000000000000000 RBX: ffff8880b8427840 RCX: ffffffff81985b4d
RDX: 00000000ffffffff RSI: 0000000000000004 RDI: ffff8880b8427840
RBP: 1ffff92000000fb6 R08: 4d4df099ab2b819a R09: 0000000000000001
R10: 0000000000000002 R11: 0000000000000000 R12: ffff8880b8427848
R13: ffff8880b8427850 R14: ffff888070874340 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff8881249df000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055558c02f650 CR3: 000000000e180000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
 atomic_try_cmpxchg_acquire include/linux/atomic/atomic-instrumented.h:1300 [inline]
 queued_spin_lock include/asm-generic/qspinlock.h:111 [inline]
 do_raw_spin_lock+0x11d/0x2b0 kernel/locking/spinlock_debug.c:116
 __run_hrtimer kernel/time/hrtimer.c:1765 [inline]
 __hrtimer_run_queues+0x2bc/0xad0 kernel/time/hrtimer.c:1825
 hrtimer_interrupt+0x397/0x8e0 kernel/time/hrtimer.c:1887
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1038 [inline]
 __sysvec_apic_timer_interrupt+0x108/0x3f0 arch/x86/kernel/apic/apic.c:1055
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1049 [inline]
 sysvec_apic_timer_interrupt+0x9f/0xc0 arch/x86/kernel/apic/apic.c:1049
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:folio_zone include/linux/mm.h:1967 [inline]
RIP: 0010:zone_stat_mod_folio include/linux/vmstat.h:432 [inline]
RIP: 0010:__folio_end_writeback+0x186/0xe60 mm/page-writeback.c:3068
Code: 89 e2 be 15 00 00 00 48 89 df e8 05 0b 33 00 9c 5d 81 e5 00 02 00 00 31 ff 48 89 ee e8 73 50 c5 ff 48 85 ed 0f 85 90 07 00 00 <e8> f5 54 c5 ff 48 89 da 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03
RSP: 0018:ffffc9000cea7950 EFLAGS: 00000293
RAX: 0000000000000000 RBX: ffffea0001f6ec40 RCX: ffffffff81f5e1a4
RDX: ffff888032bb2440 RSI: ffffffff81f5e1b2 RDI: 0000000000000007
RBP: 0000000000000000 R08: 0000000000000007 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 00000000ffffffff
R13: 0000000000000001 R14: ffffffffffffffff R15: ffffea0001f6ec00
 folio_end_writeback+0x18f/0x560 mm/filemap.c:1648
 ext4_finish_bio+0x78f/0xa20 fs/ext4/page-io.c:144
 ext4_release_io_end+0x119/0x3a0 fs/ext4/page-io.c:159
 ext4_end_io_end+0x13e/0x4a0 fs/ext4/page-io.c:210
 ext4_do_flush_completed_IO fs/ext4/page-io.c:287 [inline]
 ext4_end_io_rsv_work+0x205/0x380 fs/ext4/page-io.c:302
 process_one_work+0x9cc/0x1b70 kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3319 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3400
 kthread+0x3c2/0x780 kernel/kthread.c:464
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
rcu: rcu_preempt kthread timer wakeup didn't happen for 10501 jiffies! g6677 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=0 timer-softirq=4991
rcu: rcu_preempt kthread starved for 10502 jiffies! g6677 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=0
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:I stack:28728 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x116f/0x5de0 kernel/sched/core.c:6767
 __schedule_loop kernel/sched/core.c:6845 [inline]
 schedule+0xe7/0x3a0 kernel/sched/core.c:6860
 schedule_timeout+0x123/0x290 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x1ea/0xb00 kernel/rcu/tree.c:2046
 rcu_gp_kthread+0x270/0x380 kernel/rcu/tree.c:2248
 kthread+0x3c2/0x780 kernel/kthread.c:464
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/05/08 08:52 upstream 707df3375124 dbf35fa1 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in ext4_end_io_rsv_work
2025/12/05 02:50 upstream aa833fc394ba d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in ext4_end_io_rsv_work
2025/04/08 08:40 upstream 0af2f6be1b42 a2ada0e7 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in ext4_end_io_rsv_work
* Struck through repros no longer work on HEAD.