On Thu, Jan 13, 2022 at 4:49 PM Kenny Yu <kennyyu@xxxxxx> wrote:
>
> The next patch adds the ability to create sleepable bpf iterator programs.
> This changes `bpf_iter_run_prog` to use the appropriate synchronization for
> sleepable bpf programs. With sleepable bpf iterator programs, we can no
> longer use `rcu_read_lock()` and must use `rcu_read_lock_trace()` instead
> to protect the bpf program.
>
> Signed-off-by: Kenny Yu <kennyyu@xxxxxx>
> ---
> kernel/bpf/bpf_iter.c | 16 +++++++++++++---
> 1 file changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/bpf/bpf_iter.c b/kernel/bpf/bpf_iter.c
> index b7aef5b3416d..d814ca6454af 100644
> --- a/kernel/bpf/bpf_iter.c
> +++ b/kernel/bpf/bpf_iter.c
> @@ -5,6 +5,7 @@
> #include <linux/anon_inodes.h>
> #include <linux/filter.h>
> #include <linux/bpf.h>
> +#include <linux/rcupdate_trace.h>
>
> struct bpf_iter_target_info {
> struct list_head list;
> @@ -684,11 +685,20 @@ int bpf_iter_run_prog(struct bpf_prog *prog, void *ctx)
> {
> int ret;
>
> - rcu_read_lock();
> - migrate_disable();
> + if (prog->aux->sleepable) {
> + rcu_read_lock_trace();
Pretty cool that a single 'if' is all that is needed to enable
sleepable iterators.
Maybe combine under one 'if' ?
if (prog->aux->sleepable) {
lock_trace
migr_dis
might_fault
bpf_prog_run
migr_en
unlock_trace
} else {
lock
migr_dis
bpf_prog_run
migr_end
unlock
}
Would it be easier to read?
