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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
commit1cae13e75b7a7848c03138636d4eb8d8a5054dd5 (patch)
tree309eaf4b79e7a8e41e17175f3475d46bef57c2a6 /include/linux/percpu-refcount.h
parent2aad2a86f6685c10360ec8a5a55eb9ab7059cb72 (diff)
downloadlinux-1cae13e75b7a7848c03138636d4eb8d8a5054dd5.tar.xz
percpu_ref: make INIT_ATOMIC and switch_to_atomic() sticky
Currently, a percpu_ref which is initialized with PERPCU_REF_INIT_ATOMIC or switched to atomic mode via switch_to_atomic() automatically reverts to percpu mode on the first percpu_ref_reinit(). This makes the atomic mode difficult to use for cases where a percpu_ref is used as a persistent on/off switch which may be cycled multiple times. This patch makes such atomic state sticky so that it survives through kill/reinit cycles. After this patch, atomic state is cleared only by an explicit percpu_ref_switch_to_percpu() call. 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.h5
1 files changed, 4 insertions, 1 deletions
diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h
index b0293f268cd2..00c01fc6d88c 100644
--- a/include/linux/percpu-refcount.h
+++ b/include/linux/percpu-refcount.h
@@ -67,7 +67,9 @@ enum {
enum {
/*
* Start w/ ref == 1 in atomic mode. Can be switched to percpu
- * operation using percpu_ref_switch_to_percpu().
+ * operation using percpu_ref_switch_to_percpu(). If initialized
+ * with this flag, the ref will stay in atomic mode until
+ * percpu_ref_switch_to_percpu() is invoked on it.
*/
PERCPU_REF_INIT_ATOMIC = 1 << 0,
@@ -87,6 +89,7 @@ struct percpu_ref {
unsigned long percpu_count_ptr;
percpu_ref_func_t *release;
percpu_ref_func_t *confirm_switch;
+ bool force_atomic:1;
struct rcu_head rcu;
};