[ +Dennis for mm/pcpu ]
On 02/22/2018 05:33 PM, Eric Dumazet wrote:
> From: Eric Dumazet <[email protected]>
>
> syszbot managed to trigger RCU detected stalls in
> bpf_array_free_percpu()
>
> It takes time to allocate a huge percpu map, but even more time to free
> it.
>
> Since we run in process context, use cond_resched() to yield cpu if
> needed.
>
> Fixes: a10423b87a7e ("bpf: introduce BPF_MAP_TYPE_PERCPU_ARRAY map")
> Signed-off-by: Eric Dumazet <[email protected]>
> Reported-by: syzbot <[email protected]>
Applied to bpf tree, thanks Eric!
> ---
> kernel/bpf/arraymap.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
> diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
> index
> a364c408f25a54a8175c92b6004a5e7e15f198cb..14750e7c5ee4872e4a7426e960bea7ae001e6623
> 100644
> --- a/kernel/bpf/arraymap.c
> +++ b/kernel/bpf/arraymap.c
> @@ -26,8 +26,10 @@ static void bpf_array_free_percpu(struct bpf_array *array)
> {
> int i;
>
> - for (i = 0; i < array->map.max_entries; i++)
> + for (i = 0; i < array->map.max_entries; i++) {
> free_percpu(array->pptrs[i]);
> + cond_resched();
> + }
> }
>
> static int bpf_array_alloc_percpu(struct bpf_array *array)
> @@ -43,6 +45,7 @@ static int bpf_array_alloc_percpu(struct bpf_array *array)
> return -ENOMEM;
> }
> array->pptrs[i] = ptr;
> + cond_resched();
> }
>
> return 0;
>
