Hello,
syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in console_flush_all
EEVDF scheduling fail, picking leftmost
======================================================
WARNING: possible circular locking dependency detected
6.6.0-rc4-next-20231006-syzkaller-10238-g0f0fe5040de5 #0 Not tainted
------------------------------------------------------
syz-executor.0/5506 is trying to acquire lock:
ffffffff8d5205c0 (console_owner){....}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:301 [inline]
ffffffff8d5205c0 (console_owner){....}-{0:0}, at: srcu_read_lock_nmisafe include/linux/srcu.h:232 [inline]
ffffffff8d5205c0 (console_owner){....}-{0:0}, at: console_srcu_read_lock kernel/printk/printk.c:286 [inline]
ffffffff8d5205c0 (console_owner){....}-{0:0}, at: console_flush_all+0x154/0xec0 kernel/printk/printk.c:2952
but task is already holding lock:
ffff8880b993c318 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2a/0x140 kernel/sched/core.c:558
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #4 (&rq->__lock){-.-.}-{2:2}:
_raw_spin_lock_nested+0x31/0x40 kernel/locking/spinlock.c:378
raw_spin_rq_lock_nested+0x2a/0x140 kernel/sched/core.c:558
raw_spin_rq_lock kernel/sched/sched.h:1357 [inline]
rq_lock kernel/sched/sched.h:1671 [inline]
task_fork_fair+0x61/0x1e0 kernel/sched/fair.c:12399
sched_cgroup_fork+0x37b/0x410 kernel/sched/core.c:4799
copy_process+0x27b0/0x3fb0 kernel/fork.c:2609
kernel_clone+0x222/0x840 kernel/fork.c:2907
user_mode_thread+0x132/0x190 kernel/fork.c:2985
rest_init+0x27/0x300 init/main.c:691
arch_call_rest_init+0xe/0x10 init/main.c:823
start_kernel+0x46e/0x4f0 init/main.c:1068
x86_64_start_reservations+0x2a/0x30 arch/x86/kernel/head64.c:556
x86_64_start_kernel+0x99/0xa0 arch/x86/kernel/head64.c:537
secondary_startup_64_no_verify+0x167/0x16b
-> #3 (&p->pi_lock){-.-.}-{2:2}:
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
class_raw_spinlock_irqsave_constructor include/linux/spinlock.h:518 [inline]
try_to_wake_up+0xb5/0x1440 kernel/sched/core.c:4213
__wake_up_common+0x2a0/0x4e0 kernel/sched/wait.c:107
__wake_up_common_lock kernel/sched/wait.c:138 [inline]
__wake_up+0x11e/0x1d0 kernel/sched/wait.c:160
tty_port_default_wakeup+0xa6/0xf0 drivers/tty/tty_port.c:69
serial8250_tx_chars+0x6b7/0x8b0 drivers/tty/serial/8250/8250_port.c:1842
serial8250_handle_irq+0x549/0x700 drivers/tty/serial/8250/8250_port.c:1949
serial8250_default_handle_irq+0xcc/0x1e0 drivers/tty/serial/8250/8250_port.c:1969
serial8250_interrupt+0xa5/0x1e0 drivers/tty/serial/8250/8250_core.c:127
__handle_irq_event_percpu+0x286/0xa20 kernel/irq/handle.c:158
handle_irq_event_percpu kernel/irq/handle.c:193 [inline]
handle_irq_event+0x89/0x1f0 kernel/irq/handle.c:210
handle_edge_irq+0x249/0xbf0 kernel/irq/chip.c:831
generic_handle_irq_desc include/linux/irqdesc.h:161 [inline]
handle_irq arch/x86/kernel/irq.c:238 [inline]
__common_interrupt+0x134/0x220 arch/x86/kernel/irq.c:257
common_interrupt+0xa3/0xc0 arch/x86/kernel/irq.c:247
asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:636
lock_acquire+0x25a/0x520 kernel/locking/lockdep.c:5757
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
spin_lock include/linux/spinlock.h:351 [inline]
unix_peer_get net/unix/af_unix.c:242 [inline]
unix_dgram_sendmsg+0x2ec/0x2070 net/unix/af_unix.c:1928
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg net/socket.c:745 [inline]
__sys_sendto+0x484/0x640 net/socket.c:2194
__do_sys_sendto net/socket.c:2206 [inline]
__se_sys_sendto net/socket.c:2202 [inline]
__x64_sys_sendto+0xde/0xf0 net/socket.c:2202
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x63/0xcd
-> #2 (&tty->write_wait){-.-.}-{2:2}:
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
__wake_up_common_lock kernel/sched/wait.c:137 [inline]
__wake_up+0x101/0x1d0 kernel/sched/wait.c:160
tty_port_default_wakeup+0xa6/0xf0 drivers/tty/tty_port.c:69
serial8250_tx_chars+0x6b7/0x8b0 drivers/tty/serial/8250/8250_port.c:1842
serial8250_handle_irq+0x549/0x700 drivers/tty/serial/8250/8250_port.c:1949
serial8250_default_handle_irq+0xcc/0x1e0 drivers/tty/serial/8250/8250_port.c:1969
serial8250_interrupt+0xa5/0x1e0 drivers/tty/serial/8250/8250_core.c:127
__handle_irq_event_percpu+0x286/0xa20 kernel/irq/handle.c:158
handle_irq_event_percpu kernel/irq/handle.c:193 [inline]
handle_irq_event+0x89/0x1f0 kernel/irq/handle.c:210
handle_edge_irq+0x249/0xbf0 kernel/irq/chip.c:831
generic_handle_irq_desc include/linux/irqdesc.h:161 [inline]
handle_irq arch/x86/kernel/irq.c:238 [inline]
__common_interrupt+0x134/0x220 arch/x86/kernel/irq.c:257
common_interrupt+0xa3/0xc0 arch/x86/kernel/irq.c:247
asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:636
__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
_raw_spin_unlock_irqrestore+0xd8/0x140 kernel/locking/spinlock.c:194
spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
uart_port_unlock_irqrestore include/linux/serial_core.h:667 [inline]
serial_port_runtime_resume+0x1fe/0x2a0 drivers/tty/serial/serial_port.c:41
__rpm_callback+0x2b9/0x7a0 drivers/base/power/runtime.c:392
rpm_callback drivers/base/power/runtime.c:446 [inline]
rpm_resume+0x10ad/0x1af0 drivers/base/power/runtime.c:912
pm_runtime_work+0x147/0x210 drivers/base/power/runtime.c:977
process_one_work kernel/workqueue.c:2630 [inline]
process_scheduled_works+0x90f/0x1400 kernel/workqueue.c:2703
worker_thread+0xa5f/0xff0 kernel/workqueue.c:2784
kthread+0x2d3/0x370 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:291
-> #1 (&port_lock_key){-.-.}-{2:2}:
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
uart_port_lock_irqsave include/linux/serial_core.h:616 [inline]
serial8250_console_write+0x1a8/0x1820 drivers/tty/serial/8250/8250_port.c:3410
console_emit_next_record kernel/printk/printk.c:2894 [inline]
console_flush_all+0x7ff/0xec0 kernel/printk/printk.c:2960
console_unlock+0x13b/0x4d0 kernel/printk/printk.c:3029
vprintk_emit+0x508/0x720 kernel/printk/printk.c:2304
_printk+0xd5/0x120 kernel/printk/printk.c:2329
register_console+0x705/0xcc0 kernel/printk/printk.c:3535
univ8250_console_init+0x45/0x50 drivers/tty/serial/8250/8250_core.c:717
console_init+0x193/0x670 kernel/printk/printk.c:3681
start_kernel+0x2d2/0x4f0 init/main.c:1004
x86_64_start_reservations+0x2a/0x30 arch/x86/kernel/head64.c:556
x86_64_start_kernel+0x99/0xa0 arch/x86/kernel/head64.c:537
secondary_startup_64_no_verify+0x167/0x16b
-> #0 (console_owner){....}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain kernel/locking/lockdep.c:3868 [inline]
__lock_acquire+0x39ff/0x7f70 kernel/locking/lockdep.c:5136
lock_acquire+0x1e3/0x520 kernel/locking/lockdep.c:5753
console_lock_spinning_enable kernel/printk/printk.c:1855 [inline]
console_emit_next_record kernel/printk/printk.c:2888 [inline]
console_flush_all+0x7b2/0xec0 kernel/printk/printk.c:2960
console_unlock+0x13b/0x4d0 kernel/printk/printk.c:3029
vprintk_emit+0x508/0x720 kernel/printk/printk.c:2304
_printk+0xd5/0x120 kernel/printk/printk.c:2329
pick_eevdf+0x660/0x690 kernel/sched/fair.c:963
check_preempt_wakeup_fair+0x518/0x7b0 kernel/sched/fair.c:8108
wakeup_preempt+0xd5/0x2a0 kernel/sched/core.c:2217
wake_up_new_task+0x5f2/0xc10 kernel/sched/core.c:4857
kernel_clone+0x459/0x840 kernel/fork.c:2938
__do_sys_clone3 kernel/fork.c:3208 [inline]
__se_sys_clone3+0x2cb/0x340 kernel/fork.c:3192
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x63/0xcd
other info that might help us debug this:
Chain exists of:
console_owner --> &p->pi_lock --> &rq->__lock
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&rq->__lock);
lock(&p->pi_lock);
lock(&rq->__lock);
lock(console_owner);
*** DEADLOCK ***
4 locks held by syz-executor.0/5506:
#0: ffff888024e827b8 (&p->pi_lock){-.-.}-{2:2}, at: wake_up_new_task+0xb5/0xc10 kernel/sched/core.c:4836
#1: ffff8880b993c318 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2a/0x140 kernel/sched/core.c:558
#2: ffffffff8d407ee0 (console_lock){+.+.}-{0:0}, at: _printk+0xd5/0x120 kernel/printk/printk.c:2329
#3: ffffffff8d407b10 (console_srcu){....}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:301 [inline]
#3: ffffffff8d407b10 (console_srcu){....}-{0:0}, at: srcu_read_lock_nmisafe include/linux/srcu.h:232 [inline]
#3: ffffffff8d407b10 (console_srcu){....}-{0:0}, at: console_srcu_read_lock kernel/printk/printk.c:286 [inline]
#3: ffffffff8d407b10 (console_srcu){....}-{0:0}, at: console_flush_all+0x154/0xec0 kernel/printk/printk.c:2952
stack backtrace:
CPU: 0 PID: 5506 Comm: syz-executor.0 Not tainted 6.6.0-rc4-next-20231006-syzkaller-10238-g0f0fe5040de5 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106
check_noncircular+0x375/0x4a0 kernel/locking/lockdep.c:2187
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain kernel/locking/lockdep.c:3868 [inline]
__lock_acquire+0x39ff/0x7f70 kernel/locking/lockdep.c:5136
lock_acquire+0x1e3/0x520 kernel/locking/lockdep.c:5753
console_lock_spinning_enable kernel/printk/printk.c:1855 [inline]
console_emit_next_record kernel/printk/printk.c:2888 [inline]
console_flush_all+0x7b2/0xec0 kernel/printk/printk.c:2960
console_unlock+0x13b/0x4d0 kernel/printk/printk.c:3029
vprintk_emit+0x508/0x720 kernel/printk/printk.c:2304
_printk+0xd5/0x120 kernel/printk/printk.c:2329
pick_eevdf+0x660/0x690 kernel/sched/fair.c:963
check_preempt_wakeup_fair+0x518/0x7b0 kernel/sched/fair.c:8108
wakeup_preempt+0xd5/0x2a0 kernel/sched/core.c:2217
wake_up_new_task+0x5f2/0xc10 kernel/sched/core.c:4857
kernel_clone+0x459/0x840 kernel/fork.c:2938
__do_sys_clone3 kernel/fork.c:3208 [inline]
__se_sys_clone3+0x2cb/0x340 kernel/fork.c:3192
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7fa6ebca88d9
Code: ff ff eb d2 e8 f8 62 fd ff 0f 1f 84 00 00 00 00 00 b8 ea ff ff ff 48 85 ff 74 2c 48 85 d2 74 27 49 89 c8 b8 b3 01 00 00 0f 05 <48> 85 c0 7c 18 74 01 c3 31 ed 48 83 e4 f0 4c 89 c7 ff d2 48 89 c7
RSP: 002b:00007ffd5edf0628 EFLAGS: 00000206 ORIG_RAX: 00000000000001b3
RAX: ffffffffffffffda RBX: 00007fa6ebc50fc0 RCX: 00007fa6ebca88d9
RDX: 00007fa6ebc50fc0 RSI: 0000000000000058 RDI: 00007ffd5edf0670
RBP: 00007fa6ec9e16c0 R08: 00007fa6ec9e16c0 R09: 00007ffd5edf0757
R10: 0000000000000008 R11: 0000000000000206 R12: ffffffffffffffb0
R13: 000000000000000b R14: 00007ffd5edf0670 R15: 00007ffd5edf0758
</TASK>
Tested on:
commit: 0f0fe504 Add linux-next specific files for 20231006
git tree:
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
console output:
https://syzkaller.appspot.com/x/log.txt?x=1340d726680000
kernel config:
https://syzkaller.appspot.com/x/.config?x=1f0332e381b38553
Note: no patches were applied.