[syzbot] [kernel?] INFO: rcu detected stall in clock_adjtime (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 82714078aee4 Merge tag 'pm-6.6-rc5' of git://git.kernel.or..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=14f69da1680000
kernel config: https://syzkaller.appspot.com/x/.config?x=9246be233cb6c74a
dashboard link: https://syzkaller.appspot.com/bug?extid=628d3507228ad7472be1
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=11369379680000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12f69da1680000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9cbe1db1ea42/disk-82714078.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b1d80bc80d7d/vmlinux-82714078.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c5d39852943e/bzImage-82714078.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+628d35...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 1-...D } 2636 jiffies s: 581 root: 0x2/.
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 5044 Comm: syz-executor955 Not tainted 6.6.0-rc4-syzkaller-00229-g82714078aee4 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
RIP: 0010:__rcu_read_unlock+0x0/0x570 kernel/rcu/tree_plugin.h:419
Code: 24 10 e9 85 f8 ff ff 48 8b 7c 24 28 e8 89 25 6b 00 e9 5b fa ff ff 48 8b 7c 24 30 e8 da 24 6b 00 e9 2b fa ff ff 0f 1f 44 00 00 <f3> 0f 1e fa 41 56 41 55 41 54 55 65 48 8b 2c 25 00 bd 03 00 53 48
RSP: 0018:ffffc900003f8d88 EFLAGS: 00000046
RAX: 0000000080010001 RBX: 0000000000000001 RCX: 0000000000000000
RDX: ffff888028a6a0c0 RSI: ffffffff8864df71 RDI: 0000000000000001
RBP: ffff88807cd21410 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: dffffc0000000000 R12: 0000000000000002
R13: ffff88807cd21400 R14: ffff88807680b340 R15: ffff88807cd21000
FS: 0000555555a5f380(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000600 CR3: 0000000027216000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<NMI>
</NMI>
<IRQ>
rcu_read_unlock include/linux/rcupdate.h:781 [inline]
advance_sched+0x6c6/0xc60 net/sched/sch_taprio.c:998
__run_hrtimer kernel/time/hrtimer.c:1688 [inline]
__hrtimer_run_queues+0x203/0xc10 kernel/time/hrtimer.c:1752
hrtimer_interrupt+0x31b/0x800 kernel/time/hrtimer.c:1814
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1063 [inline]
__sysvec_apic_timer_interrupt+0x105/0x3f0 arch/x86/kernel/apic/apic.c:1080
sysvec_apic_timer_interrupt+0x8e/0xc0 arch/x86/kernel/apic/apic.c:1074
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:645
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0x31/0x70 kernel/locking/spinlock.c:194
Code: f5 53 48 8b 74 24 10 48 89 fb 48 83 c7 18 e8 56 e5 24 f7 48 89 df e8 4e 64 25 f7 f7 c5 00 02 00 00 75 1f 9c 58 f6 c4 02 75 2f <bf> 01 00 00 00 e8 55 ce 16 f7 65 8b 05 66 22 c1 75 85 c0 74 12 5b
RSP: 0018:ffffc9000350fa78 EFLAGS: 00000246
RAX: 0000000000000002 RBX: ffff8880b982b940 RCX: 1ffffffff233c916
RDX: 0000000000000000 RSI: ffffffff8a8c9ba0 RDI: ffffffff8ae90b60
RBP: 0000000000000282 R08: 0000000000000001 R09: fffffbfff233c7d0
R10: ffffffff919e3e87 R11: 0000000000000002 R12: 0000000000000004
R13: 0000000000000000 R14: 0000000000000000 R15: dffffc0000000000
clock_was_set+0x592/0x850 kernel/time/hrtimer.c:972
timekeeping_inject_offset+0x4d1/0x640 kernel/time/timekeeping.c:1395
do_adjtimex+0x373/0xaa0 kernel/time/timekeeping.c:2444
do_clock_adjtime kernel/time/posix-timers.c:1159 [inline]
__do_sys_clock_adjtime+0x173/0x280 kernel/time/posix-timers.c:1171
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7fe9265c4ee9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 d1 19 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffff514af48 EFLAGS: 00000246 ORIG_RAX: 0000000000000131
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fe9265c4ee9
RDX: 00007fe9265c4ee9 RSI: 0000000020000280 RDI: 0000000000000000
RBP: 00000000000f4240 R08: 0000000100000000 R09: 0000000100000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffff514afa0
R13: 0000000000000001 R14: 00007ffff514afa0 R15: 0000000000000003
</TASK>
INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 1.940 msecs


---
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[Hillf Danton]

On Sat, 07 Oct 2023 13:25:48 -0700

> HEAD commit: 82714078aee4 Merge tag 'pm-6.6-rc5' of git://git.kernel.or..
> git tree: upstream

> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12f69da1680000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

--- x/net/sched/sch_taprio.c
+++ y/net/sched/sch_taprio.c
@@ -991,12 +991,12 @@ first_run:
rcu_assign_pointer(q->current_entry, next);
spin_unlock(&q->current_entry_lock);

- hrtimer_set_expires(&q->advance_timer, end_time);
-
rcu_read_lock();
__netif_schedule(sch);
rcu_read_unlock();

+ hrtimer_forward_now(&q->advance_timer, ns_to_ktime(NSEC_PER_USEC *2));
+
return HRTIMER_RESTART;
}

--

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+628d35...@syzkaller.appspotmail.com

Tested on:

commit: b9ddbb0c Merge tag 'parisc-for-6.6-rc5' of git://git.k..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=125755a1680000

kernel config: https://syzkaller.appspot.com/x/.config?x=9246be233cb6c74a
dashboard link: https://syzkaller.appspot.com/bug?extid=628d3507228ad7472be1
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=121d36e9680000

Note: testing is done by a robot and is best-effort only.