Messages in this thread |  | | Date | Sun, 7 Jun 2009 12:11:36 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] scheduler: introduce SCHED_RESET_ON_FORK scheduling policy flag, Second try |
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* Lennart Poettering <mzxreary@0pointer.de> wrote:
> On Fri, 05.06.09 13:54, Ingo Molnar (mingo@elte.hu) wrote: > > > > > > > * Lennart Poettering <mzxreary@0pointer.de> wrote: > > > > > Why expose this via sched_setscheduler() and not other syscalls > > > such as prctl() or sched_setparam()? > > > > > > prctl() does not take a pid parameter. Due to that it would be > > > impossible to modify this flag for other processes than the > > > current one. > > > > > > The struct passed to sched_setparam() can unfortunately not be > > > extended without breaking compatibility, since sched_setparam() > > > lacks a size parameter. > > > > Well, it could be extended, if we wanted to. Right now > > sched_priority has a valid value of 0 to 100. We could introduce > > a new value '-1' to mean: 'extended struct sched_param'. > > > > A new getparam syscall could then be introduced - only used by > > new user-space. > > The man page of sched_getparam() is pretty explicit in that the > sched_priority field of the struct must lie between > sched_get_priority_min() and sched_get_priority_max(). If you'd > overload sched_priority like this you might end up breaking > applications that rely on this, for example RT watchdogs that go > through /proc and query the scheduling parameters of all threads.
Only the new sched_gtparam syscall would do this - and that syscall would have to be propagated to glibc and user-space with appropriate care of course. (probably resulting in a separate function not a change/breakage of existing functionality)
Probably not worth the pain though.
Ingo
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