On Fri, Nov 08 2024 at 14:32, Kunwu Chan wrote:I'am newbiee in this field. But actually when i change it to a raw spinlock, the problem syzbot reported dispeared.
When PREEMPT_RT is enabled, 'spinlock_t' becomes preemptibleThis explanation is just wrong.
and bpf program has owned a raw_spinlock under a interrupt handler,
which results in invalid lock acquire context.
The problem has nothing to do with an interrupt handler. Interrupt
handlers on RT kernels are force threaded.
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]The problematic lock nesting is the work queue pool lock, which is a raw
_raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
trie_delete_elem+0x96/0x6a0 kernel/bpf/lpm_trie.c:462
bpf_prog_2c29ac5cdc6b1842+0x43/0x47
bpf_dispatcher_nop_func include/linux/bpf.h:1290 [inline]
__bpf_prog_run include/linux/filter.h:701 [inline]
bpf_prog_run include/linux/filter.h:708 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2340 [inline]
bpf_trace_run1+0x2ca/0x520 kernel/trace/bpf_trace.c:2380
trace_workqueue_activate_work+0x186/0x1f0 include/trace/events/workqueue.h:59
__queue_work+0xc7b/0xf50 kernel/workqueue.c:2338
spinlock.
@@ -330,7 +330,7 @@ static long trie_update_elem(struct bpf_map *map,Making this a raw spinlock moves the problem from the BPF trie code into
if (key->prefixlen > trie->max_prefixlen)
return -EINVAL;
- spin_lock_irqsave(&trie->lock, irq_flags);
+ raw_spin_lock_irqsave(&trie->lock, irq_flags);
/* Allocate and fill a new node */
the memory allocator. On RT the memory allocator cannot be invoked under
a raw spinlock.
Thanks,--
tglx