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authorTejun Heo <tj@kernel.org>2014-09-24 21:31:50 +0400
committerTejun Heo <tj@kernel.org>2014-09-24 21:31:50 +0400
commit2aad2a86f6685c10360ec8a5a55eb9ab7059cb72 (patch)
tree85da25f36ba0c8158becdc8ba940201652cf30ce /include/linux/percpu-refcount.h
parentf47ad45784611297b699f3dffb6c7222b76afe64 (diff)
downloadlinux-2aad2a86f6685c10360ec8a5a55eb9ab7059cb72.tar.xz
percpu_ref: add PERCPU_REF_INIT_* flags
With the recent addition of percpu_ref_reinit(), percpu_ref now can be used as a persistent switch which can be turned on and off repeatedly where turning off maps to killing the ref and waiting for it to drain; however, there currently isn't a way to initialize a percpu_ref in its off (killed and drained) state, which can be inconvenient for certain persistent switch use cases. Similarly, percpu_ref_switch_to_atomic/percpu() allow dynamic selection of operation mode; however, currently a newly initialized percpu_ref is always in percpu mode making it impossible to avoid the latency overhead of switching to atomic mode. This patch adds @flags to percpu_ref_init() and implements the following flags. * PERCPU_REF_INIT_ATOMIC : start ref in atomic mode * PERCPU_REF_INIT_DEAD : start ref killed and drained These flags should be able to serve the above two use cases. v2: target_core_tpg.c conversion was missing. Fixed. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Kent Overstreet <kmo@daterainc.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Christoph Hellwig <hch@infradead.org> Cc: Johannes Weiner <hannes@cmpxchg.org>
Diffstat (limited to 'include/linux/percpu-refcount.h')
-rw-r--r--include/linux/percpu-refcount.h18
1 files changed, 17 insertions, 1 deletions
diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h
index cd7e20f0fe47..b0293f268cd2 100644
--- a/include/linux/percpu-refcount.h
+++ b/include/linux/percpu-refcount.h
@@ -63,6 +63,21 @@ enum {
__PERCPU_REF_FLAG_BITS = 2,
};
+/* @flags for percpu_ref_init() */
+enum {
+ /*
+ * Start w/ ref == 1 in atomic mode. Can be switched to percpu
+ * operation using percpu_ref_switch_to_percpu().
+ */
+ PERCPU_REF_INIT_ATOMIC = 1 << 0,
+
+ /*
+ * Start dead w/ ref == 0 in atomic mode. Must be revived with
+ * percpu_ref_reinit() before used. Implies INIT_ATOMIC.
+ */
+ PERCPU_REF_INIT_DEAD = 1 << 1,
+};
+
struct percpu_ref {
atomic_long_t count;
/*
@@ -76,7 +91,8 @@ struct percpu_ref {
};
int __must_check percpu_ref_init(struct percpu_ref *ref,
- percpu_ref_func_t *release, gfp_t gfp);
+ percpu_ref_func_t *release, unsigned int flags,
+ gfp_t gfp);
void percpu_ref_exit(struct percpu_ref *ref);
void percpu_ref_switch_to_atomic(struct percpu_ref *ref,
percpu_ref_func_t *confirm_switch);