On Tue, Jul 24, 2007 at 02:49:02PM +0100, David Woodhouse wrote: > Also 's/unknow /unknown /' (2 instances)
?? I didn't find them: $ grep 'unknow ' Documentation/pps/pps.txt > Am I right in thinking that the only place it matters is within > pps_event()? In that case, at the very least you should probably remove > the 'volatile' from the definition of the structure, and _cast_ to > volatile where you want it treated that way. Ok, I see. > But I don't see why you can't protect it with a spinlock. As long as you > acquire that spinlock _after_ your call to getnstimeofday() what's the > problem? The problem is that we can have several PPS sources into a system and all these sources will arise their IRQ line (quasi)simultaneously and I don't wish a CPU may delay one of these IRQ handler due a spinlock into the pps_event(). That's why I'm trying to avoid any lock into pps_event(). > I think you still haven't quite got the 32-bit vs. 64-bit compatibility > right. Remember that on i386, the alignment of a uint64_t is only 4 > bytes, while on most other architectures it's 8 bytes. On i386, there > will be no padding between the two consecutive 'struct pps_ktime' > members of struct pps_kinfo and struct pps_kparams. But on most > platforms there will be padding to ensure correct alignment. > > The simple fix is probably to make the 'nsec' member a 64-bit integer > too. Then it'll be the same for i386 and x86_64 and you won't need a > compatibility syscall routine. Ok. I'll add your comment too. > In order for your handling of 'pps_source[source].info' to be safe with > respect to pps_unregister_source(), you have to guarantee that > pps_event() has finished -- and can't be in progress on another CPU -- > by the time your client's call to pps_unregister_source() completes. At > first glance I think your existing clients have that right (you have > del_timer_sync() before pps_unregister_source() in ktimer.c, for > example). But you should make sure it's clearly documented for new > clients. This can be done only with locks, but it's not necessary since even if a pps_unregister_source() runs while pps_event() executes on another CPU the latter will write always on a valid area (even if it could be a dummy one) and the data are not corrupted (note also that the data will be, in any case, discarted since we are executing a pps_unregister_source()). > Shouldn't your PPS_CLIENT_LP and PPS_CLIENT_UART options depend on > PARPORT and SERIAL_CORE respectively? No. These options can be enabled but if no serial/parallel driver is loaded no PPS source is registered. Thanks, Rodolfo -- GNU/Linux Solutions e-mail: [EMAIL PROTECTED] Linux Device Driver [EMAIL PROTECTED] Embedded Systems [EMAIL PROTECTED] UNIX programming phone: +39 349 2432127 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
