On Thu, Dec 17, 2015 at 5:00 PM, Xin Long [off-list ref] wrote:

On Thu, Dec 17, 2015 at 4:48 PM, Herbert Xu [off-list ref] wrote:

quoted

On Thu, Dec 17, 2015 at 04:46:00PM +0800, Xin Long wrote:

quoted

sorry for late test, but unfortunately, my case with rhashtalbe still
return EBUSY.
I added some debug code in rhashtable_insert_rehash(), and found:
*future_tbl is null*

fail:
        /* Do not fail the insert if someone else did a rehash. */
        if (likely(rcu_dereference_raw(tbl->future_tbl))) {
                printk("future_tbl is there\n");
                return 0;
        } else {
                printk("future_tbl is null\n");
        }

any idea why ?

That's presumably because you got a genuine double rehash.

Until you post your code we can't really help you.

i wish i could , but my codes is a big patch for sctp, and this issue
happens in a special stress test based on this patch.
im trying to think how i can show you. :)

I'm just wondering, why do not we handle the genuine double rehash
issue inside rhashtable? i mean it's just a temporary error that a
simple retry may fix it.