On 2012-10-10 10:58, Gilles Chanteperdrix wrote: > On 10/10/2012 10:10 AM, Jan Kiszka wrote: >> On 2012-10-10 10:04, Gilles Chanteperdrix wrote: >>> On 10/10/2012 09:56 AM, Jan Kiszka wrote: >>>> On 2012-10-10 09:51, Gilles Chanteperdrix wrote: >>>>> On 10/10/2012 09:38 AM, Thierry Bultel wrote: >>>>>> Hi Gilles, >>>>>> >>>>>> Many thanks, >>>>>> The first patch does not work, the second does. >>>>>> I think the reason for 1st patch why is that in rtcan_virt, we have >>>>>> >>>>>> rtdm_lock_get_irqsave(&rtcan_recv_list_lock, lock_ctx); >>>>>> rtdm_lock_get(&rtcan_socket_lock); >>>>>> >>>>>> ... >>>>>> ---> rtcan_rcv(rx_dev, &skb); >>>>>> .... >>>>>> >>>>>> rtdm_lock_put(&rtcan_socket_lock); >>>>>> rtdm_lock_put_irqrestore(&rtcan_recv_list_lock, lock_ctx); >>>>>> >>>>>> and rtcan_rcv->rtcan_rcv_deliver->rtdm_sem_up(&sock->recv_sem); >>>>>> >>>>>> thus the same re-scheduling stuff with interrupts locked. >>>>>> >>>>>> Are you not not afraid of side effects with the second patch, >>>>>> since you change the overall behaviour ? >>>>>> Won't you prefer a only locally modified rtcan_virt ? >>>>> >>>>> We should ask Jan's opinion. In any case, if we adopt the second patch, >>>>> we might want to try and reduce the overhead of xnpod_unlock_sched. >>>>> >>>> >>>> We were signaling the semaphore while holding a spin lock? That's a >>>> clear bug. Your patch is aligning rtcan to the pattern we are also using >>>> in RTnet. We just need to make sure (haven't looked at the full context >>>> yet) that sock remains valid even after dropping the lock(s). >>> >>> The second patch idea was to lock the scheduler while spinlocks are >>> held, so that posting a semaphore while holding a spin lock is no longer >>> a bug. >> >> Sounds a bit hacky, > > Well, that is what the linux kernel does. > > but I think we have this pattern >> (RTDM_EXECUTE_ATOMICALLY) > > RTDM_EXECUTE_ATOMICALLY is a bit of a misnomer, if you do: > RTDM_EXECUTE_ATOMICALLY(foo(); rtdm_sem_up(); bar()); > foo() and bar() are not executed atomically if sem_up wakes up another > thread. > > So, I do not see how RTDM_EXECUTE_ATOMICALLY solves the issue we are > talking about.
RTDM_EXECUTE_ATOMICALLY holds the nucleus lock across the encapsulated code, executing it atomically as rescheduling is postponed until the end of the block. Jan -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 259 bytes Desc: OpenPGP digital signature URL: <http://www.xenomai.org/pipermail/xenomai/attachments/20121010/091a2ed9/attachment.pgp> _______________________________________________ Xenomai mailing list [email protected] http://www.xenomai.org/mailman/listinfo/xenomai
