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Date: Thu, 3 Oct 2013 23:10:09 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.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 10/03, Oleg Nesterov wrote:
>
> So unless Peter objects I'll write the changelogs (always nontrivial task),
> test, and send these 2 patches + "add ops->barr() / rcu_sync_wait_for_cb"
> tomorrow.
And, can't resist, probably another patch below (incomplete, needs the
obvious change in cpu.c and the new trivial __complete_locked() helper).
Hmm. But when I look at wait_for_completion() I think it is buggy. Will
try to send the fix tomorrow.
Oleg.
rcusync: introduce rcu_sync_struct->exclusive mode
CHANGELOG.
---
diff --git a/include/linux/rcusync.h b/include/linux/rcusync.h
index ab787c1..265875c 100644
--- a/include/linux/rcusync.h
+++ b/include/linux/rcusync.h
@@ -1,8 +1,8 @@
#ifndef _LINUX_RCUSYNC_H_
#define _LINUX_RCUSYNC_H_
-#include <linux/wait.h>
#include <linux/rcupdate.h>
+#include <linux/completion.h>
struct rcu_sync_ops {
void (*sync)(void);
@@ -15,11 +15,12 @@ struct rcu_sync_ops {
struct rcu_sync_struct {
int gp_state;
int gp_count;
- wait_queue_head_t gp_wait;
+ struct completion gp_comp;
int cb_state;
struct rcu_head cb_head;
+ bool exclusive;
struct rcu_sync_ops *ops;
};
@@ -33,31 +34,33 @@ static inline bool rcu_sync_is_idle(struct rcu_sync_struct *rss)
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_init(struct rcu_sync_struct *,
+ enum rcu_sync_type, bool excl);
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) { \
+#define __RCU_SYNC_INITIALIZER(name, type, excl) { \
.gp_state = 0, \
.gp_count = 0, \
- .gp_wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.gp_wait), \
+ .gp_comp = COMPLETION_INITIALIZER(name.gp_comp), \
.cb_state = 0, \
+ .exclusive = excl, \
.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, type, excl) \
+ struct rcu_sync_struct name = __RCU_SYNC_INITIALIZER(name, type, excl)
-#define DEFINE_RCU_SYNC(name) \
- __DEFINE_RCU_SYNC(name, RCU_SYNC)
+#define DEFINE_RCU_SYNC(name, excl) \
+ __DEFINE_RCU_SYNC(name, RCU_SYNC, excl)
-#define DEFINE_RCU_SCHED_SYNC(name) \
- __DEFINE_RCU_SYNC(name, RCU_SCHED_SYNC)
+#define DEFINE_RCU_SCHED_SYNC(name, excl) \
+ __DEFINE_RCU_SYNC(name, RCU_SCHED_SYNC, excl)
-#define DEFINE_RCU_BH_SYNC(name) \
- __DEFINE_RCU_SYNC(name, RCU_BH_SYNC)
+#define DEFINE_RCU_BH_SYNC(name, excl) \
+ __DEFINE_RCU_SYNC(name, RCU_BH_SYNC, excl)
#endif /* _LINUX_RCUSYNC_H_ */
diff --git a/kernel/rcusync.c b/kernel/rcusync.c
index 21cde9b..d8068df 100644
--- a/kernel/rcusync.c
+++ b/kernel/rcusync.c
@@ -4,7 +4,7 @@
enum { GP_IDLE = 0, GP_PENDING, GP_PASSED };
enum { CB_IDLE = 0, CB_PENDING, CB_REPLAY };
-#define rss_lock gp_wait.lock
+#define rss_lock gp_comp.wait.lock
#ifdef CONFIG_PROVE_RCU
#define __INIT_HELD(func) .held = func,
@@ -30,11 +30,13 @@ struct rcu_sync_ops rcu_sync_ops_array[] = {
},
};
-void rcu_sync_init(struct rcu_sync_struct *rss, enum rcu_sync_type type)
+void rcu_sync_init(struct rcu_sync_struct *rss,
+ enum rcu_sync_type type, bool excl)
{
memset(rss, 0, sizeof(*rss));
- init_waitqueue_head(&rss->gp_wait);
+ init_completion(&rss->gp_comp);
rss->ops = rcu_sync_ops_array + type;
+ rss->exclusive = excl;
}
void rcu_sync_enter(struct rcu_sync_struct *rss)
@@ -53,9 +55,13 @@ void rcu_sync_enter(struct rcu_sync_struct *rss)
if (need_sync) {
rss->ops->sync();
rss->gp_state = GP_PASSED;
- wake_up_all(&rss->gp_wait);
+ if (!rss->exclusive)
+ wake_up_all(&rss->gp_comp.wait);
} else if (need_wait) {
- wait_event(rss->gp_wait, rss->gp_state == GP_PASSED);
+ if (!rss->exclusive)
+ wait_event(rss->gp_comp.wait, rss->gp_state == GP_PASSED);
+ else
+ wait_for_completion(&rss->gp_comp);
} else {
/*
* Possible when there's a pending CB from a rcu_sync_exit().
@@ -110,6 +116,8 @@ void rcu_sync_exit(struct rcu_sync_struct *rss)
} else if (rss->cb_state == CB_PENDING) {
rss->cb_state = CB_REPLAY;
}
+ } else if (rss->exclusive) {
+ __complete_locked(&rss->gp_comp);
}
spin_unlock_irq(&rss->rss_lock);
}
--
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