diff options
Diffstat (limited to 'lib/percpu-refcount.c')
| -rw-r--r-- | lib/percpu-refcount.c | 23 |
1 files changed, 17 insertions, 6 deletions
diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c index ebeaac274cb9..8bf9e719cca0 100644 --- a/lib/percpu-refcount.c +++ b/lib/percpu-refcount.c @@ -118,6 +118,10 @@ static void percpu_ref_kill_rcu(struct rcu_head *rcu) atomic_add((int) count - PCPU_COUNT_BIAS, &ref->count); + /* @ref is viewed as dead on all CPUs, send out kill confirmation */ + if (ref->confirm_kill) + ref->confirm_kill(ref); + /* * Now we're in single atomic_t mode with a consistent refcount, so it's * safe to drop our initial ref: @@ -126,22 +130,29 @@ static void percpu_ref_kill_rcu(struct rcu_head *rcu) } /** - * percpu_ref_kill - safely drop initial ref + * percpu_ref_kill_and_confirm - drop the initial ref and schedule confirmation * @ref: percpu_ref to kill + * @confirm_kill: optional confirmation callback * - * Must be used to drop the initial ref on a percpu refcount; must be called - * precisely once before shutdown. + * Equivalent to percpu_ref_kill() but also schedules kill confirmation if + * @confirm_kill is not NULL. @confirm_kill, which may not block, will be + * called after @ref is seen as dead from all CPUs - all further + * invocations of percpu_ref_tryget() will fail. See percpu_ref_tryget() + * for more details. * - * Puts @ref in non percpu mode, then does a call_rcu() before gathering up the - * percpu counters and dropping the initial ref. + * Due to the way percpu_ref is implemented, @confirm_kill will be called + * after at least one full RCU grace period has passed but this is an + * implementation detail and callers must not depend on it. */ -void percpu_ref_kill(struct percpu_ref *ref) +void percpu_ref_kill_and_confirm(struct percpu_ref *ref, + percpu_ref_func_t *confirm_kill) { WARN_ONCE(REF_STATUS(ref->pcpu_count) == PCPU_REF_DEAD, "percpu_ref_kill() called more than once!\n"); ref->pcpu_count = (unsigned __percpu *) (((unsigned long) ref->pcpu_count)|PCPU_REF_DEAD); + ref->confirm_kill = confirm_kill; call_rcu(&ref->rcu, percpu_ref_kill_rcu); } |