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Date: Fri, 17 Jul 2015 15:20:08 -0700
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: linux-kernel@...r.kernel.org
Cc: mingo@...nel.org, laijs@...fujitsu.com, dipankar@...ibm.com,
akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
dvhart@...ux.intel.com, fweisbec@...il.com, oleg@...hat.com,
bobby.prani@...il.com,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 08/16] rcu: Create a synchronize_rcu_mult()
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
There have been several requests for a primitive that waits for
grace periods for several RCU flavors concurrently, so this
commit creates it. This is a variadic macro, and you pass in
the call_rcu() functions of the flavors of RCU that you wish to
wait for.
Note that you cannot pass in call_srcu() for two reasons: (1) This
would result in a type mismatch and (2) You need to specify which
srcu_struct you want to use. Handle this by creating a wrapper
function for your SRCU domain, for example:
void call_srcu_mine(struct rcu_head *head, rcu_callback_t func)
{
call_srcu(&ss_mine, head, func);
}
You can then do something like this:
synchronize_rcu_mult(call_srcu_mine, call_rcu, call_rcu_sched);
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
include/linux/rcupdate.h | 35 +++++++++++++++++++++++++++++++----
include/linux/types.h | 3 +++
kernel/rcu/update.c | 37 +++++++++++++++++++++++++++----------
3 files changed, 61 insertions(+), 14 deletions(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index c63428c1ed8a..33ec16b9c2ee 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -226,6 +226,37 @@ struct rcu_synchronize {
};
void wakeme_after_rcu(struct rcu_head *head);
+void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array,
+ struct rcu_synchronize *rs_array);
+
+#define _wait_rcu_gp(checktiny, ...) \
+do { \
+ call_rcu_func_t __crcu_array[] = { __VA_ARGS__ }; \
+ const int __n = ARRAY_SIZE(__crcu_array); \
+ struct rcu_synchronize __rs_array[__n]; \
+ \
+ __wait_rcu_gp(checktiny, __n, __crcu_array, __rs_array); \
+} while (0)
+
+#define wait_rcu_gp(...) _wait_rcu_gp(false, __VA_ARGS__)
+
+/**
+ * synchronize_rcu_mult - Wait concurrently for multiple grace periods
+ * @...: List of call_rcu() functions for the flavors to wait on.
+ *
+ * This macro waits concurrently for multiple flavors of RCU grace periods.
+ * For example, synchronize_rcu_mult(call_rcu, call_rcu_bh) would wait
+ * on concurrent RCU and RCU-bh grace periods. Waiting on a give SRCU
+ * domain requires you to write a wrapper function for that SRCU domain's
+ * call_srcu() function, supplying the corresponding srcu_struct.
+ *
+ * If Tiny RCU, tell _wait_rcu_gp() not to bother waiting for RCU
+ * or RCU-bh, given that anywhere synchronize_rcu_mult() can be called
+ * is automatically a grace period.
+ */
+#define synchronize_rcu_mult(...) \
+ _wait_rcu_gp(IS_ENABLED(CONFIG_TINY_RCU), __VA_ARGS__)
+
/**
* call_rcu_tasks() - Queue an RCU for invocation task-based grace period
* @head: structure to be used for queueing the RCU updates.
@@ -392,10 +423,6 @@ bool __rcu_is_watching(void);
* TREE_RCU and rcu_barrier_() primitives in TINY_RCU.
*/
-typedef void call_rcu_func_t(struct rcu_head *head,
- void (*func)(struct rcu_head *head));
-void wait_rcu_gp(call_rcu_func_t crf);
-
#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU)
#include <linux/rcutree.h>
#elif defined(CONFIG_TINY_RCU)
diff --git a/include/linux/types.h b/include/linux/types.h
index 8715287c3b1f..c314989d9158 100644
--- a/include/linux/types.h
+++ b/include/linux/types.h
@@ -212,6 +212,9 @@ struct callback_head {
};
#define rcu_head callback_head
+typedef void (*rcu_callback_t)(struct rcu_head *head);
+typedef void (*call_rcu_func_t)(struct rcu_head *head, rcu_callback_t func);
+
/* clocksource cycle base type */
typedef u64 cycle_t;
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index fec5f48b8860..a0a0dd03c73a 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -318,20 +318,37 @@ void wakeme_after_rcu(struct rcu_head *head)
rcu = container_of(head, struct rcu_synchronize, head);
complete(&rcu->completion);
}
+EXPORT_SYMBOL_GPL(wakeme_after_rcu);
-void wait_rcu_gp(call_rcu_func_t crf)
+void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array,
+ struct rcu_synchronize *rs_array)
{
- struct rcu_synchronize rcu;
+ int i;
- init_rcu_head_on_stack(&rcu.head);
- init_completion(&rcu.completion);
- /* Will wake me after RCU finished. */
- crf(&rcu.head, wakeme_after_rcu);
- /* Wait for it. */
- wait_for_completion(&rcu.completion);
- destroy_rcu_head_on_stack(&rcu.head);
+ /* Initialize and register callbacks for each flavor specified. */
+ for (i = 0; i < n; i++) {
+ if (checktiny &&
+ (crcu_array[i] == call_rcu ||
+ crcu_array[i] == call_rcu_bh)) {
+ might_sleep();
+ continue;
+ }
+ init_rcu_head_on_stack(&rs_array[i].head);
+ init_completion(&rs_array[i].completion);
+ (crcu_array[i])(&rs_array[i].head, wakeme_after_rcu);
+ }
+
+ /* Wait for all callbacks to be invoked. */
+ for (i = 0; i < n; i++) {
+ if (checktiny &&
+ (crcu_array[i] == call_rcu ||
+ crcu_array[i] == call_rcu_bh))
+ continue;
+ wait_for_completion(&rs_array[i].completion);
+ destroy_rcu_head_on_stack(&rs_array[i].head);
+ }
}
-EXPORT_SYMBOL_GPL(wait_rcu_gp);
+EXPORT_SYMBOL_GPL(__wait_rcu_gp);
#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
void init_rcu_head(struct rcu_head *head)
--
1.8.1.5
--
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