Message-ID: <6821bb38.050a0220.f2294.0056.GAE@google.com>
Date: Mon, 12 May 2025 02:11:20 -0700
From: syzbot <syzbot+bb842a51b5abbae5a245@...kaller.appspotmail.com>
To: akpm@...ux-foundation.org, linux-ext4@...r.kernel.org, 
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-mm@...ck.org, syzkaller-bugs@...glegroups.com, willy@...radead.org
Subject: [syzbot] [mm?] [ext4?] INFO: rcu detected stall in
 ext4_end_io_rsv_work (3)

Hello,

syzbot found the following issue on:

HEAD commit:    707df3375124 Merge tag 'media/v6.15-2' of git://git.kernel..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16c2a82f980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b39cb28b0a399ed3
dashboard link: https://syzkaller.appspot.com/bug?extid=bb842a51b5abbae5a245
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1050b8f4580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12a169b3980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/1920aeaaff98/disk-707df337.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5a54d789a59a/vmlinux-707df337.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e40767312770/bzImage-707df337.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bb842a51b5abbae5a245@...kaller.appspotmail.com

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>


---
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