Commit 4406942e authored by Sechang Lim's avatar Sechang Lim Committed by Alexei Starovoitov
Browse files

bpf: Fix RCU stall in bpf_fd_array_map_clear() 



Add a missing cond_resched() in bpf_fd_array_map_clear() loop.

For PROG_ARRAY maps with many entries this loop calls
prog_array_map_poke_run() per entry which can be expensive, and
without yielding this can cause RCU stalls under load:

  rcu: Stack dump where RCU GP kthread last ran:
  CPU: 0 UID: 0 PID: 30932 Comm: kworker/0:2 Not tainted 6.14.0-13195-g967e8def1100 #2 PREEMPT(undef)
  Workqueue: events prog_array_map_clear_deferred
  RIP: 0010:write_comp_data+0x38/0x90 kernel/kcov.c:246
  Call Trace:
   <TASK>
   prog_array_map_poke_run+0x77/0x380 kernel/bpf/arraymap.c:1096
   __fd_array_map_delete_elem+0x197/0x310 kernel/bpf/arraymap.c:925
   bpf_fd_array_map_clear kernel/bpf/arraymap.c:1000 [inline]
   prog_array_map_clear_deferred+0x119/0x1b0 kernel/bpf/arraymap.c:1141
   process_one_work+0x898/0x19d0 kernel/workqueue.c:3238
   process_scheduled_works kernel/workqueue.c:3319 [inline]
   worker_thread+0x770/0x10b0 kernel/workqueue.c:3400
   kthread+0x465/0x880 kernel/kthread.c:464
   ret_from_fork+0x4d/0x80 arch/x86/kernel/process.c:153
   ret_from_fork_asm+0x19/0x30 arch/x86/entry/entry_64.S:245
   </TASK>

Reviewed-by: default avatarSun Jian <sun.jian.kdev@gmail.com>
Fixes: da765a2f ("bpf: Add poke dependency tracking for prog array maps")
Signed-off-by: default avatarSechang Lim <rhkrqnwk98@gmail.com>
Link: https://lore.kernel.org/r/20260407103823.3942156-1-rhkrqnwk98@gmail.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent ae1a82e5

kernel/bpf/arraymap.c

+3 −1
Original line number Diff line number Diff line
@@ -1015,8 +1015,10 @@ static void bpf_fd_array_map_clear(struct bpf_map *map, bool need_defer) 
	struct bpf_array *array = container_of(map, struct bpf_array, map);

	int i;



	for (i = 0; i < array->map.max_entries; i++)

	for (i = 0; i < array->map.max_entries; i++) {

		__fd_array_map_delete_elem(map, &i, need_defer);

		cond_resched();

	}

}



static void prog_array_map_seq_show_elem(struct bpf_map *map, void *key,