On 10/6/25 6:22 PM, KaFai Wan wrote:
When unpinning a BPF hash table (htab or htab_lru) that contains internal structures (timer, workqueue, or task_work) in its values, a BUG warning is triggered: BUG: sleeping function called from invalid context at kernel/bpf/hashtab.c:244 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 14, name: ksoftirqd/0 ...
The issue arises from the interaction between BPF object unpinning and RCU callback mechanisms:
- BPF object unpinning uses ->free_inode() which schedules cleanup via call_rcu(), deferring the actual freeing to an RCU callback that executes within the RCU_SOFTIRQ context.
- During cleanup of hash tables containing internal structures, htab_map_free_internal_structs() is invoked, which includes cond_resched() or cond_resched_rcu() calls to yield the CPU during potentially long operations.
However, cond_resched() or cond_resched_rcu() cannot be safely called from atomic RCU softirq context, leading to the BUG warning when attempting to reschedule.
Fix this by changing from ->free_inode() to ->destroy_inode() and rename bpf_free_inode() to bpf_destroy_inode() for BPF objects (prog, map, link). This allows direct inode freeing without RCU callback scheduling, avoiding the invalid context warning.
Reported-by: Le Chen tom2cat@sjtu.edu.cn Closes: https://lore.kernel.org/all/1444123482.1827743.1750996347470.JavaMail.zimbra... Fixes: 68134668c17f ("bpf: Add map side support for bpf timers.") Suggested-by: Alexei Starovoitov ast@kernel.org Signed-off-by: KaFai Wan kafai.wan@linux.dev
Acked-by: Yonghong Song yonghong.song@linux.dev