INFO: task hung in perf_event_free_task

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: e7d2672c Linux 4.19.71
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=15dae2a5600000
kernel config: https://syzkaller.appspot.com/x/.config?x=47881f21d9108add
dashboard link: https://syzkaller.appspot.com/bug?extid=4f1587274f1d080eb3ad
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+4f1587...@syzkaller.appspotmail.com

INFO: task syz-executor.5:12480 blocked for more than 140 seconds.
Not tainted 4.19.71 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5 D26256 12480 7505 0x10000004
Call Trace:
context_switch kernel/sched/core.c:2826 [inline]
__schedule+0x866/0x1dc0 kernel/sched/core.c:3474
schedule+0x92/0x1c0 kernel/sched/core.c:3518
perf_event_free_task+0x517/0x6d0 kernel/events/core.c:11289
copy_process.part.0+0x35e6/0x7a30 kernel/fork.c:2120
copy_process kernel/fork.c:1689 [inline]
_do_fork+0x257/0xfd0 kernel/fork.c:2202
__do_sys_clone kernel/fork.c:2309 [inline]
__se_sys_clone kernel/fork.c:2303 [inline]
__x64_sys_clone+0xbf/0x150 kernel/fork.c:2303
do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4598e9
Code: Bad RIP value.
RSP: 002b:00007f150fdb8c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 00000000004598e9
RDX: 9999999999999999 RSI: 0000000000000000 RDI: 00000000004007fc
RBP: 000000000075bf20 R08: ffffffffffffffff R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f150fdb96d4
R13: 00000000004bfd7f R14: 00000000004d1b78 R15: 00000000ffffffff

Showing all locks held in the system:
1 lock held by khungtaskd/1036:
#0: 000000006e880aca (rcu_read_lock){....}, at:
debug_show_all_locks+0x5f/0x27e kernel/locking/lockdep.c:4435
1 lock held by rsyslogd/7324:
2 locks held by getty/7446:
#0: 000000001f8ca316 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 00000000b0578e00 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7447:
#0: 0000000017ae98f7 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 00000000e6d1d76e (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7448:
#0: 00000000630314c2 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 000000006a14839d (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7449:
#0: 00000000f5ae847d (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 000000000adebab1 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7450:
#0: 0000000044e3236b (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 00000000930a1cc0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7451:
#0: 00000000f00c2145 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 000000002e6d530b (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7452:
#0: 00000000d6d9927e (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 00000000b1f6827b (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 1036 Comm: khungtaskd Not tainted 4.19.71 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x172/0x1f0 lib/dump_stack.c:113
nmi_cpu_backtrace.cold+0x63/0xa4 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x1b0/0x1f8 lib/nmi_backtrace.c:62
arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:203 [inline]
watchdog+0x9df/0xee0 kernel/hung_task.c:287
kthread+0x354/0x420 kernel/kthread.c:246
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt+0xe/0x10
arch/x86/include/asm/irqflags.h:60


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.