26 May
2006
26 May
'06
2:58 a.m.
On 5/26/06, Wolfgang Woehl <tito(a)rumford.de> wrote:
Wednesday 24 May 2006 17:24, Jack O'Quin:
Some do. What we all use in the Linux world is basically POSIX
threads with fixed SCHED_FIFO priorities. These cannot be preempted
by normal SCHED_OTHER user processes. Going into a loop with
realtime priority, effectively locks out all other user processes. The
kernel can still run, but not much else. Watchdog threads are typically
provided by jackd or other mechanism, but are not built into the kernel.
--
joq
The required components are now available, and
are being provided
by a few leading-edge distributions. Had you installed Ubuntu Dapper
Drake (which is not yet officially released), you would not have seen
any problem. They chose to include the PAM patches and authorize
all users to start realtime threads be default. That is a reasonable
choice for them (given their goals), but would not be appropriate for
most other distributions.
I thought a realtime-scheduling kernel gives well-defined portions of time and
system resources to processes. Why does that mean userland could dos the
kernel? Is there no kernel watchdog that would kick out processes with
excessive demands? Does the kernel not keep a book for it's own needs?