From 478c0ba990961936269a6d44bccdbf9891a19977 Mon Sep 17 00:00:00 2001
From: alc <alc@FreeBSD.org>
Date: Mon, 29 Jul 2002 19:41:22 +0000
Subject:  o Introduce vm_page_sleep_if_busy() as an eventual replacement for  
  vm_page_sleep_busy().  vm_page_sleep_if_busy() uses the page    queues lock.

---
 sys/vm/vm_page.c | 22 ++++++++++++++++++++++
 sys/vm/vm_page.h |  1 +
 2 files changed, 23 insertions(+)

diff --git a/sys/vm/vm_page.c b/sys/vm/vm_page.c
index 1674b07..9acd481 100644
--- a/sys/vm/vm_page.c
+++ b/sys/vm/vm_page.c
@@ -552,6 +552,28 @@ vm_page_sleep_busy(vm_page_t m, int also_m_busy, const char *msg)
 	}
 	return (FALSE);
 }
+
+/*
+ *	vm_page_sleep_if_busy:
+ *
+ *	Sleep and release the page queues lock if PG_BUSY is set or,
+ *	if also_m_busy is TRUE, busy is non-zero.  Returns TRUE if the
+ *	thread slept and the page queues lock was released.
+ *	Otherwise, retains the page queues lock and returns FALSE.
+ */
+int
+vm_page_sleep_if_busy(vm_page_t m, int also_m_busy, const char *msg)
+{
+
+	mtx_assert(&vm_page_queue_mtx, MA_OWNED);
+	if ((m->flags & PG_BUSY) || (also_m_busy && m->busy)) {
+		vm_page_flag_set(m, PG_WANTED | PG_REFERENCED);
+		msleep(m, &vm_page_queue_mtx, PDROP | PVM, msg, 0);
+		return (TRUE);
+	}
+	return (FALSE);
+}
+
 /*
  *	vm_page_dirty:
  *
diff --git a/sys/vm/vm_page.h b/sys/vm/vm_page.h
index 42b4410..bd44012 100644
--- a/sys/vm/vm_page.h
+++ b/sys/vm/vm_page.h
@@ -332,6 +332,7 @@ void vm_page_copy(vm_page_t src_m, vm_page_t dest_m);
 void vm_page_free(vm_page_t m);
 void vm_page_free_zero(vm_page_t m);
 int vm_page_sleep_busy(vm_page_t m, int also_m_busy, const char *msg);
+int vm_page_sleep_if_busy(vm_page_t m, int also_m_busy, const char *msg);
 void vm_page_dirty(vm_page_t m);
 void vm_page_undirty(vm_page_t m);
 void vm_page_wakeup(vm_page_t m);
-- 
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