Messages in this thread | ![/](/images/icornerl.gif) | | Date | Sat, 15 Feb 2003 01:25:38 -0300 | From | Werner Almesberger <> | Subject | Re: Synchronous signal delivery.. |
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Giuliano Pochini wrote: > IMHO it's not simply a signal delivery system, it's a message queue.
Not entirely, because - as I understand it - signals would be aggregated, so you'd always get one item, no matter how many signals are actually pending at that time.
For generalizing such mechanisms, it might be useful to have an atomic "overwrite" operation for pipes, and maybe also for some sockets, e.g. something like this:
ssize_t overwrite(int fd, const void *data_if_empty,size_t size_if_empty, const void *data_if_full,size_t size_if_full, int *was_empty);
If there is no data in the pipe/queue, "overwrite" would write "data_if_empty", and clear *was_empty. Otherwise, it would discard what's there, then write "data_if_full", and set *was_empty. The whole operation is atomic with respect to readers/pollers.
E.g.
static int signal_set = 0;
... add_signal(int signum) { int new_signal = 1 << signum; int was_empty;
signal_set |= new_signal; overwrite(fd,&new_signal,sizeof(int),&signal_set,sizeof(int), &was_empty); if (was_empty) signal_set = new_signal; }
- Werner
-- _________________________________________________________________________ / Werner Almesberger, Buenos Aires, Argentina wa@almesberger.net / /_http://www.almesberger.net/____________________________________________/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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