From 2aad2a86f6685c10360ec8a5a55eb9ab7059cb72 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Wed, 24 Sep 2014 13:31:50 -0400 Subject: 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 Reviewed-by: Kent Overstreet Cc: Jens Axboe Cc: Christoph Hellwig Cc: Johannes Weiner --- include/linux/percpu-refcount.h | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) (limited to 'include/linux/percpu-refcount.h') 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); -- cgit v1.2.3