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Message-ID: <20131003192135.GR5790@linux.vnet.ibm.com>
Date: Thu, 3 Oct 2013 12:21:35 -0700
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: Oleg Nesterov <oleg@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>,
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 2/3] rcu: Create rcu_sync infrastructure
On Thu, Oct 03, 2013 at 08:47:19PM +0200, Oleg Nesterov wrote:
> On 10/03, Peter Zijlstra wrote:
> >
> > On Thu, Oct 03, 2013 at 09:41:17AM -0700, Paul E. McKenney wrote:
> > > On Wed, Oct 02, 2013 at 04:56:57PM +0200, Peter Zijlstra wrote:
> > > #ifdef CONFIG_PROVE_RCU
> > > #define rcu_sync_is_idle_check(rss) BUG_ON(!rss->read_side_check())
> > > #else
> > > #define rcu_sync_is_idle_check(rss) do { } while (0)
> > > #endif
> > >
> > > rcu_sync_is_idle_check(rss);
> >
> > The below actually seems to build, although I didn't test the config
> > permutations, only defconfig.
>
> Yes, but...
>
> I think it would be better to start with the patch below, this way
> it would be easier a) to add the new ops (we need more anyway) and b)
> use CONFIG_PROVE_RCU to avoid the unused members even if this is
> really minor.
I am fine with this as well, but I don't see the code that checks for
the required RCU read-side critical section.
Thanx, Paul
> Oleg.
>
> rcusync: introdude struct rcu_sync_ops
>
> CHANGELOG
>
> ---
> include/linux/rcusync.h | 63 +++++++++++++++++++++--------------------------
> kernel/rcusync.c | 40 ++++++++++++++---------------
> 2 files changed, 47 insertions(+), 56 deletions(-)
>
> diff --git a/include/linux/rcusync.h b/include/linux/rcusync.h
> index 7858491..30c6037 100644
> --- a/include/linux/rcusync.h
> +++ b/include/linux/rcusync.h
> @@ -4,6 +4,11 @@
> #include <linux/wait.h>
> #include <linux/rcupdate.h>
>
> +struct rcu_sync_ops {
> + void (*sync)(void);
> + void (*call)(struct rcu_head *, void (*)(struct rcu_head *));
> +};
> +
> struct rcu_sync_struct {
> int gp_state;
> int gp_count;
> @@ -12,43 +17,9 @@ struct rcu_sync_struct {
> int cb_state;
> struct rcu_head cb_head;
>
> - void (*sync)(void);
> - void (*call)(struct rcu_head *, void (*)(struct rcu_head *));
> + struct rcu_sync_ops *ops;
> };
>
> -#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 */
> @@ -60,5 +31,27 @@ 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 *);
>
> +extern struct rcu_sync_ops rcu_sync_ops_array[];
> +
> +#define __RCU_SYNC_INITIALIZER(name, type) { \
> + .gp_state = 0, \
> + .gp_count = 0, \
> + .gp_wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.gp_wait), \
> + .cb_state = 0, \
> + .ops = rcu_sync_ops_array + (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..1cefb83 100644
> --- a/kernel/rcusync.c
> +++ b/kernel/rcusync.c
> @@ -1,4 +1,3 @@
> -
> #include <linux/rcusync.h>
> #include <linux/sched.h>
>
> @@ -7,27 +6,26 @@ enum { CB_IDLE = 0, CB_PENDING, CB_REPLAY };
>
> #define rss_lock gp_wait.lock
>
> +struct rcu_sync_ops rcu_sync_ops_array[] = {
> + [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,
> + },
> +};
> +
> 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->ops = rcu_sync_ops_array + type;
> }
>
> void rcu_sync_enter(struct rcu_sync_struct *rss)
> @@ -44,7 +42,7 @@ void rcu_sync_enter(struct rcu_sync_struct *rss)
> BUG_ON(need_wait && need_sync);
>
> if (need_sync) {
> - rss->sync();
> + rss->ops->sync();
> rss->gp_state = GP_PASSED;
> wake_up_all(&rss->gp_wait);
> } else if (need_wait) {
> @@ -81,7 +79,7 @@ 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);
> + rss->ops->call(&rss->cb_head, rcu_sync_func);
> } else {
> /*
> * We're at least a GP after rcu_sync_exit(); eveybody will now
> @@ -99,7 +97,7 @@ 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);
> + rss->ops->call(&rss->cb_head, rcu_sync_func);
> } else if (rss->cb_state == CB_PENDING) {
> rss->cb_state = CB_REPLAY;
> }
>
--
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