Re: [PATCH] ANDROID: binder: Latelimit binder_debug().

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On Mon, Jul 9, 2018 at 3:10 AM, Tetsuo Handa
<penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote:
> While at it, let's add cond_resched() to binder_thread_write(),
> binder_transaction() and binder_release_work() loops because they might
> take long time.

This should be a separate patch, and I would love to see some
benchmark data around this change (there's a few in Android userspace
- let me know if you need help setting them up). Did you actually
observe these particular functions running for a long time without the
scheduler running?

Thanks,
Martijn

>
> [1] https://syzkaller.appspot.com/bug?id=0e75779a6f0faac461510c6330514e8f0e893038
> [2] https://syzkaller.appspot.com/bug?id=aa11d2d767f3750ef9a40d156a149e9cfa735b73
>
> Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
> Reported-by: syzbot+e38306788a2e7102a3b6@xxxxxxxxxxxxxxxxxxxxxxxxx
> Reported-by: syzbot+4417a2fa149da3802a74@xxxxxxxxxxxxxxxxxxxxxxxxx
> ---
>  drivers/android/binder.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index 95283f3..c136fce 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -161,7 +161,7 @@ static int binder_set_stop_on_user_error(const char *val,
>  #define binder_debug(mask, x...) \
>         do { \
>                 if (binder_debug_mask & mask) \
> -                       pr_info(x); \
> +                       pr_info_ratelimited(x); \
>         } while (0)
>
>  #define binder_user_error(x...) \
> @@ -3016,7 +3016,7 @@ static void binder_transaction(struct binder_proc *proc,
>         sg_bufp = (u8 *)(PTR_ALIGN(off_end, sizeof(void *)));
>         sg_buf_end = sg_bufp + extra_buffers_size;
>         off_min = 0;
> -       for (; offp < off_end; offp++) {
> +       for (; offp < off_end; cond_resched(), offp++) {
>                 struct binder_object_header *hdr;
>                 size_t object_size = binder_validate_object(t->buffer, *offp);
>
> @@ -3307,6 +3307,7 @@ static int binder_thread_write(struct binder_proc *proc,
>
>                 if (get_user(cmd, (uint32_t __user *)ptr))
>                         return -EFAULT;
> +               cond_resched();
>                 ptr += sizeof(uint32_t);
>                 trace_binder_command(cmd);
>                 if (_IOC_NR(cmd) < ARRAY_SIZE(binder_stats.bc)) {
> @@ -4193,6 +4194,7 @@ static void binder_release_work(struct binder_proc *proc,
>         struct binder_work *w;
>
>         while (1) {
> +               cond_resched();
>                 w = binder_dequeue_work_head(proc, list);
>                 if (!w)
>                         return;
> --
> 1.8.3.1
>
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