On Thu, Dec 21, 2017 at 10:08:44AM -0800, [email protected] wrote:
SNIP
> +/*
> + * Report the start and end of the available data in ringbuffer
> + */
> +int perf_mmap__read_init(struct perf_mmap *map, bool overwrite,
> + u64 *start, u64 *end)
> {
> - u64 head = perf_mmap__read_head(md);
> - u64 old = md->prev;
> - u64 end = head, start = old;
> - unsigned char *data = md->base + page_size;
> + u64 head = perf_mmap__read_head(map);
> + u64 old = map->prev;
> + unsigned char *data = map->base + page_size;
> unsigned long size;
> - void *buf;
> - int rc = 0;
>
> - start = overwrite ? head : old;
> - end = overwrite ? old : head;
> + /*
> + * Check if event was unmapped due to a POLLHUP/POLLERR.
> + */
> + if (!refcount_read(&map->refcnt))
> + return -EINVAL;
>
> - if (start == end)
> - return 0;
> + *start = overwrite ? head : old;
> + *end = overwrite ? old : head;
>
> - size = end - start;
> - if (size > (unsigned long)(md->mask) + 1) {
> + if (*start == *end)
> + return -EAGAIN;
> +
> + size = *end - *start;
> + if (size > (unsigned long)(map->mask) + 1) {
> if (!overwrite) {
> WARN_ONCE(1, "failed to keep up with mmap data. (warn
> only once)\n");
>
I know you did not change this, but is this leg even possible
in !overwrite mode? I think kernel will throw away the data,
keep the head and wait for tail to be read by user..
jirka
> - md->prev = head;
> - perf_mmap__consume(md, overwrite);
> - return 0;
> + map->prev = head;
> + perf_mmap__consume(map, overwrite);
> + return -EAGAIN;
SNIP
