Messages in this thread Patch in this message | | | From | Tejun Heo <> | Subject | [PATCH 14/14] cgroup: implement css_tryget() | Date | Fri, 9 May 2014 17:31:31 -0400 |
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Implement css_tryget() which tries to grab a cgroup_subsys_state's reference as long as it already hasn't reached zero. Combined with the recent css iterator changes to include offline && !released csses during traversal, this can be used to access csses regardless of its online state.
Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Johannes Weiner <hannes@cmpxchg.org> --- include/linux/cgroup.h | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index c8eb66e..6dd3867 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -111,6 +111,22 @@ static inline void css_get(struct cgroup_subsys_state *css) } /** + * css_tryget - try to obtain a reference on the specified css + * @css: target css + * + * Obtain a reference on @css unless it already has reached zero and is + * being released. This function doesn't care whether @css is on or + * offline. The caller naturally needs to ensure that @css is accessible + * but doesn't have to be holding a reference on it - IOW, RCU protected + * access is good enough for this function. Returns %true if a reference + * count was successfully obtained; %false otherwise. + */ +static inline bool css_tryget(struct cgroup_subsys_state *css) +{ + return percpu_ref_tryget(&css->refcnt); +} + +/** * css_tryget_online - try to obtain a reference on the specified css if online * @css: target css * -- 1.9.0
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