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Message-ID: <20131008163012.GY5790@linux.vnet.ibm.com>
Date: Tue, 8 Oct 2013 09:30:12 -0700
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Oleg Nesterov <oleg@...hat.com>, Mel Gorman <mgorman@...e.de>,
Rik van Riel <riel@...hat.com>,
Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
Ingo Molnar <mingo@...nel.org>,
Andrea Arcangeli <aarcange@...hat.com>,
Johannes Weiner <hannes@...xchg.org>,
Thomas Gleixner <tglx@...utronix.de>,
Steven Rostedt <rostedt@...dmis.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/6] rcusync: Introduce struct rcu_sync_ops
On Tue, Oct 08, 2013 at 12:25:09PM +0200, Peter Zijlstra wrote:
> From: Oleg Nesterov <oleg@...hat.com>
>
> Add the new struct rcu_sync_ops which holds sync/call methods, and
> turn the function pointers in rcu_sync_struct into an array of struct
> rcu_sync_ops.
>
> This simplifies the "init" helpers, and this way it is simpler to add
> the new methods we need, especially ifdef'ed.
>
> Signed-off-by: Peter Zijlstra <peterz@...radead.org>
> Link: http://lkml.kernel.org/r/20131005171746.GA17664@redhat.com
Reviewed-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> ---
>
> diff --git a/include/linux/rcusync.h b/include/linux/rcusync.h
> index 7858491..988ec33 100644
> --- a/include/linux/rcusync.h
> +++ b/include/linux/rcusync.h
> @@ -4,6 +4,8 @@
> #include <linux/wait.h>
> #include <linux/rcupdate.h>
>
> +enum rcu_sync_type { RCU_SYNC, RCU_SCHED_SYNC, RCU_BH_SYNC };
> +
> struct rcu_sync_struct {
> int gp_state;
> int gp_count;
> @@ -12,53 +14,37 @@ struct rcu_sync_struct {
> int cb_state;
> struct rcu_head cb_head;
>
> - void (*sync)(void);
> - void (*call)(struct rcu_head *, void (*)(struct rcu_head *));
> + enum rcu_sync_type gp_type;
> };
>
> -#define ___RCU_SYNC_INIT(name) \
> - .gp_state = 0, \
> - .gp_count = 0, \
> - .gp_wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.gp_wait), \
> - .cb_state = 0
> -
> -#define __RCU_SCHED_SYNC_INIT(name) { \
> - ___RCU_SYNC_INIT(name), \
> - .sync = synchronize_sched, \
> - .call = call_rcu_sched, \
> -}
> -
> -#define __RCU_BH_SYNC_INIT(name) { \
> - ___RCU_SYNC_INIT(name), \
> - .sync = synchronize_rcu_bh, \
> - .call = call_rcu_bh, \
> -}
> -
> -#define __RCU_SYNC_INIT(name) { \
> - ___RCU_SYNC_INIT(name), \
> - .sync = synchronize_rcu, \
> - .call = call_rcu, \
> -}
> -
> -#define DEFINE_RCU_SCHED_SYNC(name) \
> - struct rcu_sync_struct name = __RCU_SCHED_SYNC_INIT(name)
> -
> -#define DEFINE_RCU_BH_SYNC(name) \
> - struct rcu_sync_struct name = __RCU_BH_SYNC_INIT(name)
> -
> -#define DEFINE_RCU_SYNC(name) \
> - struct rcu_sync_struct name = __RCU_SYNC_INIT(name)
> -
> static inline bool rcu_sync_is_idle(struct rcu_sync_struct *rss)
> {
> return !rss->gp_state; /* GP_IDLE */
> }
>
> -enum rcu_sync_type { RCU_SYNC, RCU_SCHED_SYNC, RCU_BH_SYNC };
> -
> extern void rcu_sync_init(struct rcu_sync_struct *, enum rcu_sync_type);
> extern void rcu_sync_enter(struct rcu_sync_struct *);
> extern void rcu_sync_exit(struct rcu_sync_struct *);
>
> +#define __RCU_SYNC_INITIALIZER(name, type) { \
> + .gp_state = 0, \
> + .gp_count = 0, \
> + .gp_wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.gp_wait), \
> + .cb_state = 0, \
> + .gp_type = type, \
> + }
> +
> +#define __DEFINE_RCU_SYNC(name, type) \
> + struct rcu_sync_struct name = __RCU_SYNC_INITIALIZER(name, type)
> +
> +#define DEFINE_RCU_SYNC(name) \
> + __DEFINE_RCU_SYNC(name, RCU_SYNC)
> +
> +#define DEFINE_RCU_SCHED_SYNC(name) \
> + __DEFINE_RCU_SYNC(name, RCU_SCHED_SYNC)
> +
> +#define DEFINE_RCU_BH_SYNC(name) \
> + __DEFINE_RCU_SYNC(name, RCU_BH_SYNC)
> +
> #endif /* _LINUX_RCUSYNC_H_ */
>
> diff --git a/kernel/rcusync.c b/kernel/rcusync.c
> index f84176a..99051b7 100644
> --- a/kernel/rcusync.c
> +++ b/kernel/rcusync.c
> @@ -1,7 +1,24 @@
> -
> #include <linux/rcusync.h>
> #include <linux/sched.h>
>
> +static const struct {
> + void (*sync)(void);
> + void (*call)(struct rcu_head *, void (*)(struct rcu_head *));
> +} gp_ops[] = {
> + [RCU_SYNC] = {
> + .sync = synchronize_rcu,
> + .call = call_rcu,
> + },
> + [RCU_SCHED_SYNC] = {
> + .sync = synchronize_sched,
> + .call = call_rcu_sched,
> + },
> + [RCU_BH_SYNC] = {
> + .sync = synchronize_rcu_bh,
> + .call = call_rcu_bh,
> + },
> +};
> +
> enum { GP_IDLE = 0, GP_PENDING, GP_PASSED };
> enum { CB_IDLE = 0, CB_PENDING, CB_REPLAY };
>
> @@ -11,23 +28,7 @@ void rcu_sync_init(struct rcu_sync_struct *rss, enum rcu_sync_type type)
> {
> memset(rss, 0, sizeof(*rss));
> init_waitqueue_head(&rss->gp_wait);
> -
> - switch (type) {
> - case RCU_SYNC:
> - rss->sync = synchronize_rcu;
> - rss->call = call_rcu;
> - break;
> -
> - case RCU_SCHED_SYNC:
> - rss->sync = synchronize_sched;
> - rss->call = call_rcu_sched;
> - break;
> -
> - case RCU_BH_SYNC:
> - rss->sync = synchronize_rcu_bh;
> - rss->call = call_rcu_bh;
> - break;
> - }
> + rss->gp_type = type;
> }
>
> void rcu_sync_enter(struct rcu_sync_struct *rss)
> @@ -44,7 +45,7 @@ void rcu_sync_enter(struct rcu_sync_struct *rss)
> BUG_ON(need_wait && need_sync);
>
> if (need_sync) {
> - rss->sync();
> + gp_ops[rss->gp_type].sync();
> rss->gp_state = GP_PASSED;
> wake_up_all(&rss->gp_wait);
> } else if (need_wait) {
> @@ -81,7 +82,7 @@ static void rcu_sync_func(struct rcu_head *rcu)
> * to catch a later GP.
> */
> rss->cb_state = CB_PENDING;
> - rss->call(&rss->cb_head, rcu_sync_func);
> + gp_ops[rss->gp_type].call(&rss->cb_head, rcu_sync_func);
> } else {
> /*
> * We're at least a GP after rcu_sync_exit(); eveybody will now
> @@ -99,7 +100,7 @@ void rcu_sync_exit(struct rcu_sync_struct *rss)
> if (!--rss->gp_count) {
> if (rss->cb_state == CB_IDLE) {
> rss->cb_state = CB_PENDING;
> - rss->call(&rss->cb_head, rcu_sync_func);
> + gp_ops[rss->gp_type].call(&rss->cb_head, rcu_sync_func);
> } else if (rss->cb_state == CB_PENDING) {
> rss->cb_state = CB_REPLAY;
> }
>
>
>
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