Ingo Molnar <[EMAIL PROTECTED]> writes:
> * Jack O'Quin <[EMAIL PROTECTED]> wrote: > >> > i'm wondering, couldnt Jackd solve this whole issue completely in >> > user-space, via a simple setuid-root wrapper app that does nothing else >> > but validates whether the user is in the 'jackd' group and then keeps a >> > pipe open to to the real jackd process which it forks off, deprivileges >> > and exec()s? Then unprivileged jackd could request RT-priority changes >> > via that pipe in a straightforward way. Jack normally gets installed as >> > root/admin anyway, so it's not like this couldnt be done. >> >> Perhaps. >> >> Until recently, that didn't work because of the longstanding rlimits >> bug in mlockall(). For scheduling only, it might be possible. >> >> Of course, this violates your requirement that the user not be able to >> lock up the CPU for DoS. The jackd watchdog is not perfect. > > there is a legitimate fear that if it's made "too easy" to acquire some > sort of SCHED_FIFO priority, that an "arm's race" would begin between > desktop apps, each trying to set themselves to SCHED_FIFO (or SCHED_ISO) > and advising users to 'raise the limit if they see delays' - just to get > snappier than the rest. > > thus after a couple of years we'd end up with lots of desktop apps > running as SCHED_FIFO, and latency would go down the drain again.
I wonder how Mac OS X and Windows deal with this priority escalation problem? Is it real or only theoretical?
WRT the Mac, I thought OS X was created to cure the ills of cooperative multi-tasking. (which the priority arms race reminds me of)
-Mike
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