From 696704716d52a895094da20b7e1a0f763b069e12 Mon Sep 17 00:00:00 2001 From: jhb Date: Fri, 2 Jul 2004 20:21:44 +0000 Subject: 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) --- sys/sys/interrupt.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'sys/sys/interrupt.h') diff --git a/sys/sys/interrupt.h b/sys/sys/interrupt.h index 7f7ddef..28d6413 100644 --- a/sys/sys/interrupt.h +++ b/sys/sys/interrupt.h @@ -122,7 +122,7 @@ int ithread_add_handler(struct ithd *ithread, const char *name, driver_intr_t handler, void *arg, u_char pri, enum intr_type flags, void **cookiep); int ithread_remove_handler(void *cookie); -int ithread_schedule(struct ithd *ithread, int do_switch); +int ithread_schedule(struct ithd *ithread); int swi_add(struct ithd **ithdp, const char *name, driver_intr_t handler, void *arg, int pri, enum intr_type flags, void **cookiep); -- cgit v1.1