On 2/4/19 7:55 PM, Jan Kiszka wrote:
>> - * Release the lock while copying the data to
>> - * keep latency low.
>> + * We have to drop the lock while reading in
>> + * data, but we can't rollback on bad read
>> + * from user because some other thread might
>> + * have populated the memory ahead of our
>> + * write slot already: bluntly clear the
>> + * unavailable bytes on copy error.
>> */
>> cobalt_atomic_leave(s);
>> - ret = xnbufd_copy_to_kmem(rsk->bufmem + wroff, bufd, n);
>> - if (ret < 0)
>> - return ret;
>> + xret = xnbufd_copy_to_kmem(rsk->bufmem + wroff, bufd, n);
>> cobalt_atomic_enter(s);
>> - /*
>> - * In case we were preempted while copying the
>> - * message, we have to write the whole thing
>> - * again.
>> - */
>> - if (rsk->wrtoken != wrtoken) {
>> - xnbufd_reset(bufd);
>> - goto redo;
>> + if (xret < 0) {
>> + memset(rsk->bufmem + wroff + n - xret, 0, xret);
>
> This looks fishy, to the compiler and also to me.
>
Oh, well. Paste© blunder, the fix originates from a distinct
co-kernel implementation. I'll resubmit.
--
Philippe.
