GitHub-Mirror/Star64_linux
2
0
Fork 0
mirror of https://github.com/Fishwaldo/Star64_linux.git synced 2025-06-20 13:41:30 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions

percpu-refcount: require percpu_ref to be exited explicitly

Browse source 
Currently, a percpu_ref undoes percpu_ref_init() automatically by
freeing the allocated percpu area when the percpu_ref is killed.
While seemingly convenient, this has the following niggles.

* It's impossible to re-init a released reference counter without
  going through re-allocation.

* In the similar vein, it's impossible to initialize a percpu_ref
  count with static percpu variables.

* We need and have an explicit destructor anyway for failure paths -
  percpu_ref_cancel_init().

This patch removes the automatic percpu counter freeing in
percpu_ref_kill_rcu() and repurposes percpu_ref_cancel_init() into a
generic destructor now named percpu_ref_exit().  percpu_ref_destroy()
is considered but it gets confusing with percpu_ref_kill() while
"exit" clearly indicates that it's the counterpart of
percpu_ref_init().

All percpu_ref_cancel_init() users are updated to invoke
percpu_ref_exit() instead and explicit percpu_ref_exit() calls are
added to the destruction path of all percpu_ref users.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Benjamin LaHaise <bcrl@kvack.org>
Cc: Kent Overstreet <kmo@daterainc.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: Nicholas A. Bellinger <nab@linux-iscsi.org>
Cc: Li Zefan <lizefan@huawei.com>
This commit is contained in:
Tejun Heo 2014-06-28 08:10:14 -04:00
parent 7d74207512
commit 9a1049da9b
5 changed files with 24 additions and 33 deletions
Download patch file Download diff file Expand all files Collapse all files

33
lib/percpu-refcount.c
View file

@ -61,36 +61,25 @@ int percpu_ref_init(struct percpu_ref *ref, percpu_ref_func_t *release)
EXPORT_SYMBOL_GPL(percpu_ref_init);
/**
* percpu_ref_cancel_init - cancel percpu_ref_init()
* @ref: percpu_ref to cancel init for
* percpu_ref_exit - undo percpu_ref_init()
* @ref: percpu_ref to exit
*
* 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().
* This function exits @ref. The caller is responsible for ensuring that
* @ref is no longer in active use. The usual places to invoke this
* function from are the @ref->release() callback or in init failure path
* where percpu_ref_init() succeeded but other parts of the initialization
* of the embedding object failed.
*/
void percpu_ref_cancel_init(struct percpu_ref *ref)
void percpu_ref_exit(struct percpu_ref *ref)
{
unsigned __percpu *pcpu_count = pcpu_count_ptr(ref);
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(pcpu_count);
ref->pcpu_count_ptr = PCPU_REF_DEAD;
}
}
EXPORT_SYMBOL_GPL(percpu_ref_cancel_init);
EXPORT_SYMBOL_GPL(percpu_ref_exit);
static void percpu_ref_kill_rcu(struct rcu_head *rcu)
{
@ -102,8 +91,6 @@ static void percpu_ref_kill_rcu(struct rcu_head *rcu)
for_each_possible_cpu(cpu)
count += *per_cpu_ptr(pcpu_count, cpu);
free_percpu(pcpu_count);
pr_debug("global %i pcpu %i", atomic_read(&ref->count), (int) count);
/*