On Wed, 2013-03-20 at 02:42 +0400, Ilya Zykov wrote: > On 20.03.2013 0:21, Peter Hurley wrote: > > Ldisc interface functions must be called with interrupts enabled. > > Separating the ldisc calls into a helper function simplies the > > spin lock management. > > > > Update the buffer's read index _after_ the data has been received > > by the ldisc. > > > > Hello Peter! > It looks good for me. > I think also we can remove two variables without waste: > (char_buf), (flag_buf) and use without (&buf->lock) > (head->char_buf_ptr + head->read), (head->char_buf_ptr + head->read), > because (head->read) guarded by (TTYP_FLUSHING). Hi Ilya, Good to hear from you again. Yes, I agree, head->read can be safely read and modified here without owning the buf->lock. And as you correctly point out, there is no need to make a snapshot of the buf pointers so those locals can be removed. I'll redo this patch to add both those suggestions. Thanks! > I have little question about flush_to_ldisc(). > Does can it be multithreaded? > > I think yes, because on SMP schedule_work() can work on different CPU paralleled. Yes, the same work item can now run in parallel on SMP since Tejun Heo re-did the workqueue implementation on 2.6.36 [Stefan Richter, the firewire maintainer, recently explained this history to me]. > What do you think about this race condition? > https://lkml.org/lkml/2011/11/7/98 Yes, that is a possible race condition that could lead to some nasty results. Good find. If you want, I could bring that patch into this patchset or you could re-submit that patch to Greg and I could rebase this patchset on top of that. Regards, Peter Hurley -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
