Signed-off-by: Mathieu Desnoyers <[email protected]>
---
tracker_private.h | 3 ++-
wrapper/freelist-ll.h | 21 +++++++++++++++------
2 files changed, 17 insertions(+), 7 deletions(-)
diff --git a/tracker_private.h b/tracker_private.h
index 03386b8..fc27f80 100644
--- a/tracker_private.h
+++ b/tracker_private.h
@@ -7,6 +7,7 @@
#include <linux/workqueue.h>
#include <linux/irq_work.h>
+#include <asm/local.h>
//#include "wrapper/ht.h"
//#include "rculfhash-internal.h"
@@ -18,7 +19,7 @@ struct numa_pool {
};
struct per_cpu_ll {
- int current_count;
+ local_t current_count;
struct numa_pool *pool;
struct llist_head llist;
};
diff --git a/wrapper/freelist-ll.h b/wrapper/freelist-ll.h
index 5e4d18e..44db722 100644
--- a/wrapper/freelist-ll.h
+++ b/wrapper/freelist-ll.h
@@ -242,8 +242,8 @@ int free_per_cpu_llist(struct latency_tracker *tracker)
if (!list)
continue;
cnt = free_event_list(list);
- printk("freed %d on cpu %d (%d)\n", cnt, cpu,
- ll->current_count);
+ printk("freed %d on cpu %d (%ld)\n", cnt, cpu,
+ local_read(&ll->current_count));
total_cnt += cnt;
}
@@ -284,10 +284,14 @@ struct llist_node *per_cpu_get(struct latency_tracker
*tracker)
struct per_cpu_ll *ll;
ll = lttng_this_cpu_ptr(tracker->per_cpu_ll);
+ /*
+ * Decrement the current count after we successfully remove an
+ * element from the list.
+ */
node = llist_del_first(&ll->llist);
if (node) {
- ll->current_count--;
- WARN_ON_ONCE(ll->current_count < 0);
+ local_dec(&ll->current_count);
+ WARN_ON_ONCE(local_read(&ll->current_count) < 0);
return node;
}
return llist_del_first(&ll->pool->llist);
@@ -336,12 +340,17 @@ void __wrapper_freelist_put_event(struct latency_tracker
*tracker,
if (e->pool != ll->pool) {
// printk("DEBUG cross-pool put_event\n");
llist_add(&e->llist, &ll->pool->llist);
- } else if (ll->current_count < FREELIST_PERCPU_CACHE) {
+ } else if (local_read(&ll->current_count) < FREELIST_PERCPU_CACHE) {
/*
* Fill our local cache if needed.
+ * We need to increment current_count before we add the
+ * element to the list, because when we successfully
+ * remove an element from the list, we expect that the
+ * counter is never negative. An interrupt can observe
+ * the intermediate state.
*/
+ local_inc(&ll->current_count);
llist_add(&e->llist, &ll->llist);
- ll->current_count++;
} else {
/*
* Add to our NUMA pool.
--
2.1.4
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