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dpif-netdev: Reintroduce ref_cnt for dp_netdev_flow

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struct dp_netdev_flow used to have a reference counter.
It has been replaced by RCU. Unfortunately RCU is not
enough if we plan to hold a reference to the dp_netdev_flow
for a long time. So this commit reintroduces reference
counting for struct dp_netdev_flow

Subsequent commits make use of it.

Signed-off-by: Daniele Di Proietto <ddiproietto@vmware.com>
Acked-by: Pravin B Shelar <pshelar@nicira.com>
This commit is contained in:
Daniele Di Proietto
2014-08-11 17:25:50 -07:00
committed by Pravin B Shelar
parent 52d2957040
commit ed79f89a30
1 changed files with 23 additions and 9 deletions
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32
lib/dpif-netdev.c
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@@ -219,15 +219,13 @@ struct netdev_flow_key {
* Rules
* -----
*
* A flow 'flow' may be accessed without a risk of being freed by code that
* holds a read-lock or write-lock on 'cls->rwlock' or that owns a reference to
* 'flow->ref_cnt' (or both). Code that needs to hold onto a flow for a while
* should take 'cls->rwlock', find the flow it needs, increment 'flow->ref_cnt'
* with dpif_netdev_flow_ref(), and drop 'cls->rwlock'.
* A flow 'flow' may be accessed without a risk of being freed during an RCU
* grace period. Code that needs to hold onto a flow for a while
* should try incrementing 'flow->ref_cnt' with dp_netdev_flow_ref().
*
* 'flow->ref_cnt' protects 'flow' from being freed. It doesn't protect the
* flow from being deleted from 'cls' (that's 'cls->rwlock') and it doesn't
* protect members of 'flow' from modification.
* flow from being deleted from 'cls' and it doesn't protect members of 'flow'
* from modification.
*
* Some members, marked 'const', are immutable. Accessing other members
* requires synchronization, as noted in more detail below.
@@ -240,6 +238,12 @@ struct dp_netdev_flow {
const struct cmap_node node; /* In owning dp_netdev's 'flow_table'. */
const struct flow flow; /* The flow that created this entry. */
/* Number of references.
* The classifier owns one reference.
* Any thread trying to keep a rule from being freed should hold its own
* reference. */
struct ovs_refcount ref_cnt;
/* Statistics.
*
* Reading or writing these members requires 'mutex'. */
@@ -249,7 +253,7 @@ struct dp_netdev_flow {
OVSRCU_TYPE(struct dp_netdev_actions *) actions;
};
static void dp_netdev_flow_free(struct dp_netdev_flow *);
static void dp_netdev_flow_unref(struct dp_netdev_flow *);
/* Contained by struct dp_netdev_flow's 'stats' member. */
struct dp_netdev_flow_stats {
@@ -907,6 +911,13 @@ dp_netdev_flow_free(struct dp_netdev_flow *flow)
free(flow);
}
static void dp_netdev_flow_unref(struct dp_netdev_flow *flow)
{
if (ovs_refcount_unref_relaxed(&flow->ref_cnt) == 1) {
ovsrcu_postpone(dp_netdev_flow_free, flow);
}
}
static void
dp_netdev_remove_flow(struct dp_netdev *dp, struct dp_netdev_flow *flow)
OVS_REQUIRES(dp->flow_mutex)
@@ -916,7 +927,8 @@ dp_netdev_remove_flow(struct dp_netdev *dp, struct dp_netdev_flow *flow)
classifier_remove(&dp->cls, cr);
cmap_remove(&dp->flow_table, node, flow_hash(&flow->flow, 0));
ovsrcu_postpone(dp_netdev_flow_free, flow);
dp_netdev_flow_unref(flow);
}
static void
@@ -1219,6 +1231,8 @@ dp_netdev_flow_add(struct dp_netdev *dp, struct match *match,
netdev_flow = xzalloc(sizeof *netdev_flow);
*CONST_CAST(struct flow *, &netdev_flow->flow) = match->flow;
ovs_refcount_init(&netdev_flow->ref_cnt);
ovsthread_stats_init(&netdev_flow->stats);
ovsrcu_set(&netdev_flow->actions,