Messages in this thread | | | Date | Wed, 11 Nov 1998 04:09:32 +0100 (CET) | From | MOLNAR Ingo <> | Subject | Re: Schedule idle |
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On Tue, 10 Nov 1998, Gordon P. Oliver wrote:
> _please_ We can do better than this. Only semaphores (not spinlocks) need > to have the priority inheritance. [...]
nope there are _not_ only semaphores, but many other types of locks.
> [...] This can be done with lists off the > semaphore and tasks... [...]
it's _not_ easy to extend Linux semaphores to handle priority inheritance. currently semaphore operations can be done via hw-atomic test-and-set instructions. If we do anything more complex, we cannot use simple instructions anymore. Linux semaphores are 2 instructions for an up() and 2 for a down(), and thats one of our crown jewels :)
the whole point is not quite valid, RT and filesystem IO doesnt mix well anyway ... the solution: use system calls that are guaranteed to not block, either by design, or by system policy (ie. separate filesystem on a RAMDISK) ... or use a device that doesnt introduce large latencies. (RAMdisk or solid state disk)
-- mingo
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