EVL defines five scheduling policies for running out-of-band threads in user space. Only two of them are available to EVL kernel threads, namely:
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SCHED_FIFO, which is the common first-in, first-out real-time policy.
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SCHED_WEAK, which is a non real-time policy.
The scheduling policy of an EVL kernel thread is defined at creation time by the priority argument passed to the evl_run_kthread() call.
Scheduler services
This is the rescheduling procedure for kernel space code, which is the
equivalent of the schedule() from the in-band kernel. When and where
to call it follows this rule of thumb:
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evl_schedule() MUST be called to apply the changes to the scheduler state caused by any primitive service which wakes up a thread, such as evl_wake_up(), or EVL services suffixed by
_noschedwhich explicitly refrain from calling the rescheduling procedure, such as evl_raise_flag_nosched(). -
there is NO need to call evl_schedule() after any EVL routine which is known to block the caller.
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a code path MUST NOT call evl_schedule() while holding a spinlock.
