Make getpbuf(), trypbuf(), and relpbuf() MPSAFE.

diff --git a/sys/vm/vm_pager.c b/sys/vm/vm_pager.c
index 59edb02..d64ba6a 100644 (file)
--- a/sys/vm/vm_pager.c
+++ b/sys/vm/vm_pager.c
@@ -181,6 +181,7 @@ struct vm_map pager_map;
 static int bswneeded;
 static vm_offset_t swapbkva;           /* swap buffers kva */
 static TAILQ_HEAD(swqueue, buf) bswlist;
+static struct spinlock bswspin = SPINLOCK_INITIALIZER(&bswspin);
 
 void
 vm_pager_init(void)
@@ -334,7 +335,7 @@ initpbuf(struct buf *bp)
 }
 
 /*
- * allocate a physical buffer
+ * Allocate a physical buffer
  *
  *     There are a limited number (nswbuf) of physical buffers.  We need
  *     to make sure that no single subsystem is able to hog all of them,
@@ -347,59 +348,62 @@ initpbuf(struct buf *bp)
  *
  *     NOTE: pfreecnt can be NULL, but this 'feature' will be removed
  *     relatively soon when the rest of the subsystems get smart about it. XXX
+ *
+ * MPSAFE
  */
 struct buf *
 getpbuf(int *pfreecnt)
 {
        struct buf *bp;
 
-       crit_enter();
+       spin_lock_wr(&bswspin);
 
        for (;;) {
                if (pfreecnt) {
-                       while (*pfreecnt == 0) {
-                               tsleep(pfreecnt, 0, "wswbuf0", 0);
-                       }
+                       while (*pfreecnt == 0)
+                               msleep(pfreecnt, &bswspin, 0, "wswbuf0", 0);
                }
 
                /* get a bp from the swap buffer header pool */
                if ((bp = TAILQ_FIRST(&bswlist)) != NULL)
                        break;
-
                bswneeded = 1;
-               tsleep(&bswneeded, 0, "wswbuf1", 0);
+               msleep(&bswneeded, &bswspin, 0, "wswbuf1", 0);
                /* loop in case someone else grabbed one */
        }
        TAILQ_REMOVE(&bswlist, bp, b_freelist);
        if (pfreecnt)
                --*pfreecnt;
-       crit_exit();
+
+       spin_unlock_wr(&bswspin);
 
        initpbuf(bp);
        return bp;
 }
 
 /*
- * allocate a physical buffer, if one is available.
+ * Allocate a physical buffer, if one is available.
  *
  *     Note that there is no NULL hack here - all subsystems using this
  *     call understand how to use pfreecnt.
+ *
+ * MPSAFE
  */
 struct buf *
 trypbuf(int *pfreecnt)
 {
        struct buf *bp;
 
-       crit_enter();
+       spin_lock_wr(&bswspin);
+
        if (*pfreecnt == 0 || (bp = TAILQ_FIRST(&bswlist)) == NULL) {
-               crit_exit();
+               spin_unlock_wr(&bswspin);
                return NULL;
        }
        TAILQ_REMOVE(&bswlist, bp, b_freelist);
-
        --*pfreecnt;
 
-       crit_exit();
+       spin_unlock_wr(&bswspin);
 
        initpbuf(bp);
 
@@ -407,29 +411,39 @@ trypbuf(int *pfreecnt)
 }
 
 /*
- * release a physical buffer
+ * Release a physical buffer
  *
  *     NOTE: pfreecnt can be NULL, but this 'feature' will be removed
  *     relatively soon when the rest of the subsystems get smart about it. XXX
+ *
+ * MPSAFE
  */
 void
 relpbuf(struct buf *bp, int *pfreecnt)
 {
-       crit_enter();
+       int wake_bsw = 0;
+       int wake_freecnt = 0;
 
        KKASSERT(bp->b_flags & B_PAGING);
-       BUF_UNLOCK(bp);
 
-       TAILQ_INSERT_HEAD(&bswlist, bp, b_freelist);
+       spin_lock_wr(&bswspin);
 
+       BUF_UNLOCK(bp);
+       TAILQ_INSERT_HEAD(&bswlist, bp, b_freelist);
        if (bswneeded) {
                bswneeded = 0;
-               wakeup(&bswneeded);
+               wake_bsw = 1;
        }
        if (pfreecnt) {
                if (++*pfreecnt == 1)
-                       wakeup(pfreecnt);
+                       wake_freecnt = 1;
        }
-       crit_exit();
+
+       spin_unlock_wr(&bswspin);
+
+       if (wake_bsw)
+               wakeup(&bswneeded);
+       if (wake_freecnt)
+               wakeup(pfreecnt);
 }