Re: [BUG] -next lockdep invalid wait context

[Hillf Danton <hdanton@sina.com>]

On Thu, 31 Oct 2024 08:21:36 +0100 Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> On 2024-10-30 16:10:58 [-0700], Paul E. McKenney wrote:
> > 
> > So I need to avoid calling kfree() within an smp_call_function() handler?
> 
> Yes. No kmalloc()/ kfree() in IRQ context.
> 
Another splat [1] with no link to kmalloc()/ kfree(). 

[ BUG: Invalid wait context ]
6.12.0-rc5-next-20241031-syzkaller #0 Not tainted
-----------------------------
strace-static-x/5846 is trying to lock:
ffffffff8eac8698 (kernfs_rename_lock){....}-{3:3}, at: kernfs_path_from_node+0x92/0xb00 fs/kernfs/dir.c:229
other info that might help us debug this:
context-{5:5}
3 locks held by strace-static-x/5846:
 #0: ffff8880b873e598 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2a/0x140 kernel/sched/core.c:598
 #1: ffffffff8e939f20 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline]
 #1: ffffffff8e939f20 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #1: ffffffff8e939f20 (rcu_read_lock){....}-{1:3}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2339 [inline]
 #1: ffffffff8e939f20 (rcu_read_lock){....}-{1:3}, at: bpf_trace_run2+0x1fc/0x540 kernel/trace/bpf_trace.c:2381
 #2: ffff88802f7129e0 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_trylock include/linux/mmap_lock.h:208 [inline]
 #2: ffff88802f7129e0 (&mm->mmap_lock){++++}-{4:4}, at: stack_map_get_build_id_offset+0x431/0x870 kernel/bpf/stackmap.c:157

[1] Subject: [syzbot] [kernfs?] WARNING: locking bug in kernfs_path_from_node
https://lore.kernel.org/lkml/67251dc6.050a0220.529b6.015e.GAE@google.com/