block/replication: drop extra synchronization

[qemu.git] / util / qsp.c

diff --git a/util/qsp.c b/util/qsp.c
index b0c2575d108668aa6cfea14e1cb8b5201a8bbe46..a848b09c6def800c29e9f597ff844e3efb497055 100644 (file)
--- a/util/qsp.c
+++ b/util/qsp.c
@@ -84,13 +84,6 @@ struct QSPEntry {
     uint64_t n_acqs;
     uint64_t ns;
     unsigned int n_objs; /* count of coalesced objs; only used for reporting */
     uint64_t n_acqs;
     uint64_t ns;
     unsigned int n_objs; /* count of coalesced objs; only used for reporting */

-#ifndef CONFIG_ATOMIC64
-    /*
-     * If we cannot update the counts atomically, then use a seqlock.
-     * We don't need an associated lock because the updates are thread-local.
-     */
-    QemuSeqLock sequence;
-#endif

 };
 typedef struct QSPEntry QSPEntry;
 
 };
 typedef struct QSPEntry QSPEntry;
 


@@ -344,47 +337,16 @@ static QSPEntry *qsp_entry_get(const void *obj, const char *file, int line,
     return qsp_entry_find(&qsp_ht, &orig, hash);
 }
 
     return qsp_entry_find(&qsp_ht, &orig, hash);
 }
 

-/*
- * @from is in the global hash table; read it atomically if the host
- * supports it, otherwise use the seqlock.
- */
-static void qsp_entry_aggregate(QSPEntry *to, const QSPEntry *from)
-{
-#ifdef CONFIG_ATOMIC64
-    to->ns += atomic_read__nocheck(&from->ns);
-    to->n_acqs += atomic_read__nocheck(&from->n_acqs);
-#else
-    unsigned int version;
-    uint64_t ns, n_acqs;
-
-    do {
-        version = seqlock_read_begin(&from->sequence);
-        ns = atomic_read__nocheck(&from->ns);
-        n_acqs = atomic_read__nocheck(&from->n_acqs);
-    } while (seqlock_read_retry(&from->sequence, version));
-
-    to->ns += ns;
-    to->n_acqs += n_acqs;
-#endif
-}
-

 /*
  * @e is in the global hash table; it is only written to by the current thread,
  * so we write to it atomically (as in "write once") to prevent torn reads.
 /*
  * @e is in the global hash table; it is only written to by the current thread,
  * so we write to it atomically (as in "write once") to prevent torn reads.

- * If the host doesn't support u64 atomics, use the seqlock.

  */
 static inline void do_qsp_entry_record(QSPEntry *e, int64_t delta, bool acq)
 {
  */
 static inline void do_qsp_entry_record(QSPEntry *e, int64_t delta, bool acq)
 {

-#ifndef CONFIG_ATOMIC64
-    seqlock_write_begin(&e->sequence);
-#endif
-    atomic_set__nocheck(&e->ns, e->ns + delta);
+    atomic_set_u64(&e->ns, e->ns + delta);

     if (acq) {
     if (acq) {

-        atomic_set__nocheck(&e->n_acqs, e->n_acqs + 1);
+        atomic_set_u64(&e->n_acqs, e->n_acqs + 1);

     }
     }

-#ifndef CONFIG_ATOMIC64
-    seqlock_write_end(&e->sequence);
-#endif

 }
 
 static inline void qsp_entry_record(QSPEntry *e, int64_t delta)
 }
 
 static inline void qsp_entry_record(QSPEntry *e, int64_t delta)


@@ -533,7 +495,7 @@ static gint qsp_tree_cmp(gconstpointer ap, gconstpointer bp, gpointer up)
     }
 }
 
     }
 }
 

-static void qsp_sort(struct qht *ht, void *p, uint32_t h, void *userp)
+static void qsp_sort(void *p, uint32_t h, void *userp)

 {
     QSPEntry *e = p;
     GTree *tree = userp;
 {
     QSPEntry *e = p;
     GTree *tree = userp;


@@ -541,7 +503,7 @@ static void qsp_sort(struct qht *ht, void *p, uint32_t h, void *userp)
     g_tree_insert(tree, e, NULL);
 }
 
     g_tree_insert(tree, e, NULL);
 }
 

-static void qsp_aggregate(struct qht *global_ht, void *p, uint32_t h, void *up)
+static void qsp_aggregate(void *p, uint32_t h, void *up)

 {
     struct qht *ht = up;
     const QSPEntry *e = p;
 {
     struct qht *ht = up;
     const QSPEntry *e = p;


@@ -550,10 +512,15 @@ static void qsp_aggregate(struct qht *global_ht, void *p, uint32_t h, void *up)
 
     hash = qsp_entry_no_thread_hash(e);
     agg = qsp_entry_find(ht, e, hash);
 
     hash = qsp_entry_no_thread_hash(e);
     agg = qsp_entry_find(ht, e, hash);

-    qsp_entry_aggregate(agg, e);
+    /*
+     * The entry is in the global hash table; read from it atomically (as in
+     * "read once").
+     */
+    agg->ns += atomic_read_u64(&e->ns);
+    agg->n_acqs += atomic_read_u64(&e->n_acqs);

 }
 
 }
 

-static void qsp_iter_diff(struct qht *orig, void *p, uint32_t hash, void *htp)
+static void qsp_iter_diff(void *p, uint32_t hash, void *htp)

 {
     struct qht *ht = htp;
     QSPEntry *old = p;
 {
     struct qht *ht = htp;
     QSPEntry *old = p;


@@ -583,8 +550,7 @@ static void qsp_diff(struct qht *orig, struct qht *new)
     qht_iter(orig, qsp_iter_diff, new);
 }
 
     qht_iter(orig, qsp_iter_diff, new);
 }
 

-static void
-qsp_iter_callsite_coalesce(struct qht *orig, void *p, uint32_t h, void *htp)
+static void qsp_iter_callsite_coalesce(void *p, uint32_t h, void *htp)

 {
     struct qht *ht = htp;
     QSPEntry *old = p;
 {
     struct qht *ht = htp;
     QSPEntry *old = p;


@@ -603,7 +569,7 @@ qsp_iter_callsite_coalesce(struct qht *orig, void *p, uint32_t h, void *htp)
     e->n_acqs += old->n_acqs;
 }
 
     e->n_acqs += old->n_acqs;
 }
 

-static void qsp_ht_delete(struct qht *ht, void *p, uint32_t h, void *htp)
+static void qsp_ht_delete(void *p, uint32_t h, void *htp)

 {
     g_free(p);
 }
 {
     g_free(p);
 }