qht: add qht_iter_remove

This currently has no users, but the use case is so common that I
think we must support it.

Note that without the appended we cannot safely remove a set of
elements; a 2-step approach (i.e. qht_iter first, keep track of
the to-be-deleted elements, and then a bunch of qht_remove calls)
would be racy, since between the iteration and the removals other
threads might insert additional elements.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/include/qemu/qht.h b/include/qemu/qht.h
index c9a11cc29a..3a9618db69 100644
--- a/include/qemu/qht.h
+++ b/include/qemu/qht.h
@@ -44,6 +44,8 @@ struct qht_stats {
 
 typedef bool (*qht_lookup_func_t)(const void *obj, const void *userp);
 typedef void (*qht_iter_func_t)(struct qht *ht, void *p, uint32_t h, void *up);
+typedef bool (*qht_iter_bool_func_t)(struct qht *ht, void *p, uint32_t h,
+                                     void *up);
 
 #define QHT_MODE_AUTO_RESIZE 0x1 /* auto-resize when heavily loaded */
 #define QHT_MODE_RAW_MUTEXES 0x2 /* bypass the profiler (QSP) */
@@ -179,10 +181,27 @@ bool qht_resize(struct qht *ht, size_t n_elems);
  *
  * Each time it is called, user-provided @func is passed a pointer-hash pair,
  * plus @userp.
+ *
+ * Note: @ht cannot be accessed from @func
+ * See also: qht_iter_remove()
  */
 void qht_iter(struct qht *ht, qht_iter_func_t func, void *userp);
 
 /**
+ * qht_iter_remove - Iterate over a QHT, optionally removing entries
+ * @ht: QHT to be iterated over
+ * @func: function to be called for each entry in QHT
+ * @userp: additional pointer to be passed to @func
+ *
+ * Each time it is called, user-provided @func is passed a pointer-hash pair,
+ * plus @userp. If @func returns true, the pointer-hash pair is removed.
+ *
+ * Note: @ht cannot be accessed from @func
+ * See also: qht_iter()
+ */
+void qht_iter_remove(struct qht *ht, qht_iter_bool_func_t func, void *userp);
+
+/**
  * qht_statistics_init - Gather statistics from a QHT
  * @ht: QHT to gather statistics from
  * @stats: pointer to a &struct qht_stats to be filled in