From: Matthew Dillon <dillon@apollo.backplane.com>
Date: Fri, 28 Oct 2011 16:27:20 +0000 (-0700)
Subject: kernel - add lwkt_set_interrupt_support_thread() API
X-Git-Url: https://gitweb.dragonflybsd.org/~lentferj/dragonfly.git/commitdiff_plain/e6546af9e0ddd006849722f5ea6b457fdf1771f5

kernel - add lwkt_set_interrupt_support_thread() API

* Add a new API that may be used by a device driver's support thread
  to run the thread at a higher (near interrupt) priority and allow
  it to preempt normal threads.

* Adjust the AHCI driver's helper threads to use the new API.
---

diff --git a/sys/dev/disk/ahci/ahci_dragonfly.c b/sys/dev/disk/ahci/ahci_dragonfly.c
index 55d524bb90..a550644db6 100644
--- a/sys/dev/disk/ahci/ahci_dragonfly.c
+++ b/sys/dev/disk/ahci/ahci_dragonfly.c
@@ -367,6 +367,12 @@ ahci_port_thread(void *arg)
 	struct ahci_port *ap = arg;
 	int mask;
 
+	/*
+	 * Sets us up as an interrupt support thread, meaning we are
+	 * given a higher priority and we can preempt normal threads.
+	 */
+	lwkt_set_interrupt_support_thread();
+
 	/*
 	 * The helper thread is responsible for the initial port init,
 	 * so all the ports can be inited in parallel.
diff --git a/sys/kern/lwkt_thread.c b/sys/kern/lwkt_thread.c
index e3dd7705ce..c55ebdd827 100644
--- a/sys/kern/lwkt_thread.c
+++ b/sys/kern/lwkt_thread.c
@@ -1117,12 +1117,6 @@ lwkt_preempt(thread_t ntd, int critcount)
     KKASSERT(ntd->td_preempted && (td->td_flags & TDF_PREEMPT_DONE));
     ntd->td_preempted = NULL;
     td->td_flags &= ~(TDF_PREEMPT_LOCK|TDF_PREEMPT_DONE);
-#if 1
-    /*
-     * catch-all
-     */
-    splz_check();
-#endif
 }
 
 /*
@@ -1166,6 +1160,22 @@ lwkt_maybe_splz(thread_t td)
     }
 }
 
+/*
+ * Drivers which set up processing co-threads can call this function to
+ * run the co-thread at a higher priority and to allow it to preempt
+ * normal threads.
+ */
+void
+lwkt_set_interrupt_support_thread(void)
+{
+	thread_t td = curthread;
+
+        lwkt_setpri_self(TDPRI_INT_SUPPORT);
+	td->td_flags |= TDF_INTTHREAD;
+	td->td_preemptable = lwkt_preempt;
+}
+
+
 /*
  * This function is used to negotiate a passive release of the current
  * process/lwp designation with the user scheduler, allowing the user
diff --git a/sys/sys/thread.h b/sys/sys/thread.h
index 9e1baadbb0..0f2259516a 100644
--- a/sys/sys/thread.h
+++ b/sys/sys/thread.h
@@ -405,6 +405,7 @@ extern void lwkt_init(void);
 extern struct thread *lwkt_alloc_thread(struct thread *, int, int, int);
 extern void lwkt_init_thread(struct thread *, void *, int, int,
 			     struct globaldata *);
+extern void lwkt_set_interrupt_support_thread(void);
 extern void lwkt_set_comm(thread_t, const char *, ...) __printflike(2, 3);
 extern void lwkt_wait_free(struct thread *);
 extern void lwkt_free_thread(struct thread *);