diff options
author | Tejun Heo <tj@kernel.org> | 2013-06-12 20:52:35 -0700 |
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committer | Tejun Heo <tj@kernel.org> | 2013-06-13 11:08:27 -0700 |
commit | bc497bd33b2d6a6f07bc8574b4764edbd7fdffa8 (patch) | |
tree | 2425880399cae042dcb7bf9c4fefdbdaf67f6ab5 /lib | |
parent | acac7883ee7bcc32476963bce7baf73d44574dd1 (diff) | |
download | linux-bc497bd33b2d6a6f07bc8574b4764edbd7fdffa8.tar.bz2 |
percpu-refcount: implement percpu_ref_cancel_init()
Normally, percpu_ref_init() initializes and percpu_ref_kill()
initiates destruction which completes asynchronously. The
asynchronous destruction can be problematic in init failure path where
the caller wants to destroy half-constructed object - distinguishing
half-constructed objects from the usual release method can be painful
for complex objects.
This patch implements percpu_ref_cancel_init() which synchronously
destroys the percpu_ref without invoking release. To avoid
unintentional misuses, the function requires the ref to have finished
percpu_ref_init() but never used and triggers WARN otherwise.
v2: Explain the weird name and usage restriction in the function
comment.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Kent Overstreet <koverstreet@google.com>
Diffstat (limited to 'lib')
-rw-r--r-- | lib/percpu-refcount.c | 31 |
1 files changed, 31 insertions, 0 deletions
diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c index b35eaac2954f..ebeaac274cb9 100644 --- a/lib/percpu-refcount.c +++ b/lib/percpu-refcount.c @@ -54,6 +54,37 @@ int percpu_ref_init(struct percpu_ref *ref, percpu_ref_func_t *release) return 0; } +/** + * percpu_ref_cancel_init - cancel percpu_ref_init() + * @ref: percpu_ref to cancel init for + * + * Once a percpu_ref is initialized, its destruction is initiated by + * percpu_ref_kill() and completes asynchronously, which can be painful to + * do when destroying a half-constructed object in init failure path. + * + * This function destroys @ref without invoking @ref->release and the + * memory area containing it can be freed immediately on return. To + * prevent accidental misuse, it's required that @ref has finished + * percpu_ref_init(), whether successful or not, but never used. + * + * The weird name and usage restriction are to prevent people from using + * this function by mistake for normal shutdown instead of + * percpu_ref_kill(). + */ +void percpu_ref_cancel_init(struct percpu_ref *ref) +{ + unsigned __percpu *pcpu_count = ref->pcpu_count; + int cpu; + + WARN_ON_ONCE(atomic_read(&ref->count) != 1 + PCPU_COUNT_BIAS); + + if (pcpu_count) { + for_each_possible_cpu(cpu) + WARN_ON_ONCE(*per_cpu_ptr(pcpu_count, cpu)); + free_percpu(ref->pcpu_count); + } +} + static void percpu_ref_kill_rcu(struct rcu_head *rcu) { struct percpu_ref *ref = container_of(rcu, struct percpu_ref, rcu); |