On Thu, Jul 26, 2007 at 12:22:31PM -0400, Frank Ch. Eigler wrote: > Hi - > > On Thu, Jul 26, 2007 at 11:02:26AM -0400, Mathieu Desnoyers wrote: > > [...] > > > > The problem is also in _stp_print_flush, not *only* in relay code: > > > > void _stp_print_flush (void) > > > > ... > > > > spin_lock(&_stp_print_lock); > > > > spin_unlock(&_stp_print_lock); > > > > > > > > Those will turn into mutexes with -rt. > > > > > > Indeed, > > (Though actually that bug was fixed some time ago.) > > > > > plus systemtap-generated locking code uses rwlocks, > > > local_irq_save/restore or preempt_disable, in various places. Could > > > someone point to a place that spells out what would be more > > > appropriate way of ensuring atomicity while being compatible with -rt? > > > > AFAIK, for your needs either: > > [...] > > - Use per-cpu data with preempt disabling/irq disabling > > As in local_irq_save / preempt_disable? Yes, already done. > > > - Use the original "real" spin locks/rwlocks (raw_*). > > [...] > > It was unclear from the OLS paper whether the spin_lock_irq* family of > functions also had to be moved to the raw forms. By making the locks of the raw_* type, spin_lock_irq* functions would then automatically disable hardware interrupts. > > > You just don't want to sleep in the tracing code. [...] Since you > > will likely disable preemption, make sure your tracing code executes > > in a deterministic time. > > Definitely, that has always been the case. > > > Make sure that the sub-buffer switch code respects that too [...] > > We will review that part of the related code. > > - FChE -- Regards, Ankita Garg (ankita@xxxxxxxxxx) Linux Technology Center IBM India Systems & Technology Labs, Bangalore, India - To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
