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authorLinus Torvalds <torvalds@linux-foundation.org>2014-06-09 14:56:07 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-06-09 14:56:07 -0700
commit68a29ef2e3f0edd154c3f5093e3c9ec772e4011f (patch)
treeb2c0594c16acbcb4b1905abac518110be5c4e69b
parent963649d735c8b6eb0f97e82c54f02426ff3f1f45 (diff)
parent315c5554c406fdad404a99dfefc931db0df80692 (diff)
Merge branch 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu
Pull percpu updates from Tejun Heo: "Nothing too exciting. percpu_ref is going through some interface changes and getting new features with more changes in the pipeline but given its young age and few users, it's very low impact" * 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu: percpu-refcount: implement percpu_ref_tryget() percpu-refcount: rename percpu_ref_tryget() to percpu_ref_tryget_live() percpu: Replace __get_cpu_var with this_cpu_ptr
-rw-r--r--include/linux/cgroup.h2
-rw-r--r--include/linux/percpu-refcount.h34
-rw-r--r--include/linux/percpu.h2
3 files changed, 35 insertions, 3 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index d60904b9e505..bddebc5cf8e7 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -101,7 +101,7 @@ static inline bool css_tryget(struct cgroup_subsys_state *css)
{
if (css->flags & CSS_ROOT)
return true;
- return percpu_ref_tryget(&css->refcnt);
+ return percpu_ref_tryget_live(&css->refcnt);
}
/**
diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h
index 0afb48fd449d..5d8920e23073 100644
--- a/include/linux/percpu-refcount.h
+++ b/include/linux/percpu-refcount.h
@@ -121,6 +121,36 @@ static inline void percpu_ref_get(struct percpu_ref *ref)
* percpu_ref_tryget - try to increment a percpu refcount
* @ref: percpu_ref to try-get
*
+ * Increment a percpu refcount unless its count already reached zero.
+ * Returns %true on success; %false on failure.
+ *
+ * The caller is responsible for ensuring that @ref stays accessible.
+ */
+static inline bool percpu_ref_tryget(struct percpu_ref *ref)
+{
+ unsigned __percpu *pcpu_count;
+ int ret = false;
+
+ rcu_read_lock_sched();
+
+ pcpu_count = ACCESS_ONCE(ref->pcpu_count);
+
+ if (likely(REF_STATUS(pcpu_count) == PCPU_REF_PTR)) {
+ this_cpu_inc(*pcpu_count);
+ ret = true;
+ } else {
+ ret = atomic_inc_not_zero(&ref->count);
+ }
+
+ rcu_read_unlock_sched();
+
+ return ret;
+}
+
+/**
+ * percpu_ref_tryget_live - try to increment a live percpu refcount
+ * @ref: percpu_ref to try-get
+ *
* Increment a percpu refcount unless it has already been killed. Returns
* %true on success; %false on failure.
*
@@ -128,8 +158,10 @@ static inline void percpu_ref_get(struct percpu_ref *ref)
* will fail. For such guarantee, percpu_ref_kill_and_confirm() should be
* used. After the confirm_kill callback is invoked, it's guaranteed that
* no new reference will be given out by percpu_ref_tryget().
+ *
+ * The caller is responsible for ensuring that @ref stays accessible.
*/
-static inline bool percpu_ref_tryget(struct percpu_ref *ref)
+static inline bool percpu_ref_tryget_live(struct percpu_ref *ref)
{
unsigned __percpu *pcpu_count;
int ret = false;
diff --git a/include/linux/percpu.h b/include/linux/percpu.h
index 495c6543a8f2..8419053d0f2e 100644
--- a/include/linux/percpu.h
+++ b/include/linux/percpu.h
@@ -29,7 +29,7 @@
*/
#define get_cpu_var(var) (*({ \
preempt_disable(); \
- &__get_cpu_var(var); }))
+ this_cpu_ptr(&var); }))
/*
* The weird & is necessary because sparse considers (void)(var) to be