John Baldwin 0c0b25ae91 Implement preemption of kernel threads natively in the scheduler rather ... than as one-off hacks in various other parts of the kernel: - Add a function maybe_preempt() that is called from sched_add() to determine if a thread about to be added to a run queue should be preempted to directly. If it is not safe to preempt or if the new thread does not have a high enough priority, then the function returns false and sched_add() adds the thread to the run queue. If the thread should be preempted to but the current thread is in a nested critical section, then the flag TDF_OWEPREEMPT is set and the thread is added to the run queue. Otherwise, mi_switch() is called immediately and the thread is never added to the run queue since it is switch to directly. When exiting an outermost critical section, if TDF_OWEPREEMPT is set, then clear it and call mi_switch() to perform the deferred preemption. - Remove explicit preemption from ithread_schedule() as calling setrunqueue() now does all the correct work. This also removes the do_switch argument from ithread_schedule(). - Do not use the manual preemption code in mtx_unlock if the architecture supports native preemption. - Don't call mi_switch() in a loop during shutdown to give ithreads a chance to run if the architecture supports native preemption since the ithreads will just preempt DELAY(). - Don't call mi_switch() from the page zeroing idle thread for architectures that support native preemption as it is unnecessary. - Native preemption is enabled on the same archs that supported ithread preemption, namely alpha, i386, and amd64. This change should largely be a NOP for the default case as committed except that we will do fewer context switches in a few cases and will avoid the run queues completely when preempting. Approved by: scottl (with his re@ hat)		2004-07-02 20:21:44 +00:00
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alpha	Implement preemption of kernel threads natively in the scheduler rather	2004-07-02 20:21:44 +00:00
compile
conf	Add option GEOM_GPT. This brings the ability to have a large number of	2004-05-02 20:40:19 +00:00
include	Implement preemption of kernel threads natively in the scheduler rather	2004-07-02 20:21:44 +00:00
isa	Catch up with __RMAN_RESOURCE_VISIBLE enough to get GENERIC to build	2004-07-01 15:07:27 +00:00
linux	Regenerate.	2004-06-04 13:52:51 +00:00
mcbus	Catch up with __RMAN_RESOURCE_VISIBLE enough to get GENERIC to build	2004-07-01 15:07:27 +00:00
osf1	- Replace wait1() with a kern_wait() function that accepts the pid,	2004-03-17 20:00:00 +00:00
pci	Catch up with __RMAN_RESOURCE_VISIBLE enough to get GENERIC to build	2004-07-01 15:07:27 +00:00
tlsb	Catch up with __RMAN_RESOURCE_VISIBLE enough to get GENERIC to build	2004-07-01 15:07:27 +00:00
Makefile