checkpoint some RCU changes

374fe0a0 · Frans Kaashoek · 6600eed0 · 374fe0a0 · 374fe0a0 · 374fe0a0
--- a/defs.h
+++ b/defs.h
@@ -134,6 +134,8 @@ void            migrate(void);

 // rcu.c
 void            rcuinit(void);
+void            rcu_begin_write(struct spinlock *);
+void            rcu_end_write(struct spinlock *);

 // swtch.S
 void            swtch(struct context**, struct context*);

--- a/main.c
+++ b/main.c
@@ -50,8 +50,8 @@ mainc(void)
  consoleinit();   // I/O devices & their interrupts
  uartinit();      // serial port
  kvmalloc();      // initialize the kernel page table
-  nsinit();        // initialize name space module
  rcuinit();       // initialize rcu module
+  nsinit();        // initialize name space module
  pinit();         // process table
  tvinit();        // trap vectors
  binit();         // buffer cache

--- a/ns.c
+++ b/ns.c
@@ -4,8 +4,13 @@
 #include "queue.h"

 // name spaces
+// XXX maybe use open hash table, no chain, better cache locality

 #define NHASH 100
+static int rcu = 0;
+
+#define ACQUIRE(l) (rcu) ? rcu_begin_write(l) : acquire(l)
+#define RELEASE(l) (rcu) ? rcu_end_write(l) : release(l)

 // XXX cache align
 struct elem {
@@ -39,11 +44,12 @@ nsalloc(void)
 {
  struct ns *ns = 0;

-  acquire(&ns_lock);
  ns = kmalloc(sizeof(struct ns));
  if (ns == 0)
    panic("nsalloc");
  memset(ns, 0, sizeof(struct ns));
+
+  acquire(&ns_lock);
  for (int i = 0; i < NHASH; i++) {
    TAILQ_INIT(&ns->table[i].chain);
  }
@@ -74,7 +80,7 @@ int
 ns_insert(struct ns *ns, int key, void *val) 
 {
  int r = -1;
-  acquire(&ns->lock);
+  ACQUIRE(&ns->lock);
  struct elem *e = elemalloc();
  if (e) {
    e->key = key;
@@ -83,7 +89,7 @@ ns_insert(struct ns *ns, int key, void *val)
    TAILQ_INSERT_TAIL(&(ns->table[i].chain), e, chain);
    r = 0;
  }
-  release(&ns->lock);
+  RELEASE(&ns->lock);
  return r;
 }

@@ -103,9 +109,9 @@ ns_dolookup(struct ns *ns, int key)
 void*
 ns_lookup(struct ns *ns, int key)
 {
-  acquire(&ns->lock);
+  ACQUIRE(&ns->lock);
  struct elem *e = ns_dolookup(ns, key);
-  release(&ns->lock);
+  RELEASE(&ns->lock);
  return (e == 0)? 0 : e->val;
 }

@@ -113,14 +119,14 @@ int
 ns_remove(struct ns *ns, int key)
 {
  int r = -1;
-  acquire(&ns->lock);
+  ACQUIRE(&ns->lock);
  struct elem *e = ns_dolookup(ns, key);
  if (e) {
    TAILQ_REMOVE(&(ns->table[key % NHASH].chain), e, chain);
    kmfree(e);
    r = 0;
  }
-  release(&ns->lock);
+  RELEASE(&ns->lock);
  return r;
 }


--- a/rcu.c
+++ b/rcu.c
@@ -10,8 +10,6 @@

 #define NRCU 1000

-#define NDELAY 500
-
 struct rcu {
  void *item;
  unsigned long epoch;
@@ -37,10 +35,11 @@ rcuinit(void)
  initlock(&rcu_lock, "rcu");
  for (i = 0; i < NRCU; i++) {
    r = (struct rcu *) kmalloc(sizeof(struct rcu));
+    memset(r, 0, sizeof(struct rcu));
    r->rcu = rcu_freelist;
    rcu_freelist = r;
  }
-  cprintf("rcu_init: allocated %ld bytes\n", sizeof(struct rcu) * NRCU);
+  cprintf("rcu_init: allocated %d bytes\n", sizeof(struct rcu) * NRCU);
 }

 struct rcu *
@@ -71,7 +70,11 @@ rcu_gc(void)
  int n = 0;
  min_epoch = global_epoch;

+
+  acquire(&rcu_lock);
+
  ns_enumerate(nspid, rcu_min);
+
  for (r = rcu_delayed_head; r != NULL; r = nr) {
    if (r->epoch >= min_epoch)
      break;
@@ -93,6 +96,7 @@ rcu_gc(void)
    r->rcu = rcu_freelist;
    rcu_freelist = r;
  }
+  release(&rcu_lock);
  //  printf("rcu_gc: n=%d ndelayed_free=%d nfree=%d ninuse=%d\n", n, delayed_nfree, 
  //	 tree_nfree, tree_ninuse);
 }
@@ -108,40 +112,42 @@ rcu_delayed(void *e, void (*dofree)(void *))
  r->item = e;
  r->rcu = 0;
  r->epoch = global_epoch;
+  acquire(&rcu_lock);
  //  printf("rcu_delayed: %ld\n", global_epoch);
  if (rcu_delayed_tail != 0) 
    rcu_delayed_tail->rcu = r;
  rcu_delayed_tail = r;
  if (rcu_delayed_head == 0) rcu_delayed_head = r;
+  release(&rcu_lock);
  delayed_nfree++;
  ninuse--;
 }

 void
-rcu_begin_read(int tid)
+rcu_begin_read()
 {
  proc->epoch = global_epoch;
  __sync_synchronize();
 }

 void
-rcu_end_read(int tid)
+rcu_end_read()
 {
  proc->epoch = INF;
 }

 void
-rcu_begin_write(int tid)
+rcu_begin_write(struct spinlock *l)
 {
-  acquire(&rcu_lock);
+  acquire(l);
 }

 void
-rcu_end_write(int tid)
+rcu_end_write(struct spinlock *l)
 {
  // for other data structures using rcu, use atomic add:
  __sync_fetch_and_add(&global_epoch, 1);
+  release(l);
  rcu_gc();
-  release(&rcu_lock);
 }