percpu-refcount: improve WARN messages

percpu_ref's WARN messages can be a lot more helpful by indicating
who's the culprit.  Make them report the release function that the
offending percpu-refcount is associated with.  This should make it a
lot easier to track down the reported invalid refcnting operations.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Kent Overstreet <kmo@daterainc.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c
index ff9903264a91..70d28c91f35a 100644
--- a/lib/percpu-refcount.c
+++ b/lib/percpu-refcount.c
@@ -145,8 +145,9 @@ static void percpu_ref_kill_rcu(struct rcu_head *rcu)
 
         atomic_add((int) count - PCPU_COUNT_BIAS, &ref->count);
 
-        WARN_ONCE(atomic_read(&ref->count) <= 0, "percpu ref <= 0 (%i)",
-                  atomic_read(&ref->count));
+        WARN_ONCE(atomic_read(&ref->count) <= 0,
+                  "percpu ref (%pf) <= 0 (%i) after killed",
+                  ref->release, atomic_read(&ref->count));
 
         /* @ref is viewed as dead on all CPUs, send out kill confirmation */
         if (ref->confirm_kill)
@@ -178,7 +179,8 @@ void percpu_ref_kill_and_confirm(struct percpu_ref *ref,
                                  percpu_ref_func_t *confirm_kill)
 {
         WARN_ONCE(ref->pcpu_count_ptr & PCPU_REF_DEAD,
-                  "percpu_ref_kill() called more than once!\n");
+                  "percpu_ref_kill() called more than once on %pf!",
+                  ref->release);
 
         ref->pcpu_count_ptr |= PCPU_REF_DEAD;
         ref->confirm_kill = confirm_kill;