Re: WARNING: suspicious RCU usage in count
From: Matthew Wilcox
Date: Wed Dec 16 2020 - 15:56:36 EST
On Wed, Dec 16, 2020 at 11:34:10AM -0800, syzbot wrote:
> Unfortunately, I don't have any reproducer for this issue yet.
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+51ce7a5794c3b12a70d1@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> =============================
> WARNING: suspicious RCU usage
> 5.10.0-rc7-syzkaller #0 Not tainted
> -----------------------------
> kernel/sched/core.c:7270 Illegal context switch in RCU-bh read-side critical section!
>
> other info that might help us debug this:
>
>
> rcu_scheduler_active = 2, debug_locks = 0
> no locks held by udevd/9038.
>
> stack backtrace:
> CPU: 3 PID: 9038 Comm: udevd Not tainted 5.10.0-rc7-syzkaller #0
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
> Call Trace:
> __dump_stack lib/dump_stack.c:77 [inline]
> dump_stack+0x107/0x163 lib/dump_stack.c:118
> ___might_sleep+0x220/0x2b0 kernel/sched/core.c:7270
> count.constprop.0+0x164/0x270 fs/exec.c:449
> do_execveat_common+0x2fd/0x7c0 fs/exec.c:1893
> do_execve fs/exec.c:1983 [inline]
> __do_sys_execve fs/exec.c:2059 [inline]
> __se_sys_execve fs/exec.c:2054 [inline]
> __x64_sys_execve+0x8f/0xc0 fs/exec.c:2054
> do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
This must be the victim of something else. There's no way this call
trace took the RCU read lock.