linux-kernel - [PATCH 1/1] rcu_sync: Cleanup the CONFIG_PROVE

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Message-ID: <20150911155918.GA27250@redhat.com>
Date:	Fri, 11 Sep 2015 17:59:18 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Davidlohr Bueso <dave@...olabs.net>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/1] rcu_sync: Cleanup the CONFIG_PROVE_RCU checks

1. Rename __rcu_sync_is_idle() to rcu_sync_lockdep_assert() and
   change it to use rcu_lockdep_assert().

2. Change rcu_sync_is_idle() to return rsp->gp_state == GP_IDLE
   unconditonally, this way we can remove the same check from
   rcu_sync_lockdep_assert() and clearly isolate the debugging
   code.

Note: rcu_sync_enter()->wait_event(gp_state == GP_PASSED) needs
another CONFIG_PROVE_RCU check, the same we do in ->sync(); but
this needs some simple preparations in the core RCU code to avoid
the code duplication.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 include/linux/rcu_sync.h |    7 +++----
 kernel/rcu/sync.c        |    6 +++---
 2 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/include/linux/rcu_sync.h b/include/linux/rcu_sync.h
index 8069d64..a63a33e 100644
--- a/include/linux/rcu_sync.h
+++ b/include/linux/rcu_sync.h
@@ -40,7 +40,7 @@ struct rcu_sync {
 	enum rcu_sync_type	gp_type;
 };
 
-extern bool __rcu_sync_is_idle(struct rcu_sync *);
+extern void rcu_sync_lockdep_assert(struct rcu_sync *);
 
 /**
  * rcu_sync_is_idle() - Are readers permitted to use their fastpaths?
@@ -53,10 +53,9 @@ extern bool __rcu_sync_is_idle(struct rcu_sync *);
 static inline bool rcu_sync_is_idle(struct rcu_sync *rsp)
 {
 #ifdef CONFIG_PROVE_RCU
-	return __rcu_sync_is_idle(rsp);
-#else
-	return !rsp->gp_state; /* GP_IDLE */
+	rcu_sync_lockdep_assert(rsp);
 #endif
+	return !rsp->gp_state; /* GP_IDLE */
 }
 
 extern void rcu_sync_init(struct rcu_sync *, enum rcu_sync_type);
diff --git a/kernel/rcu/sync.c b/kernel/rcu/sync.c
index 1c73c57..a8cf199 100644
--- a/kernel/rcu/sync.c
+++ b/kernel/rcu/sync.c
@@ -63,10 +63,10 @@ enum { CB_IDLE = 0, CB_PENDING, CB_REPLAY };
 #define	rss_lock	gp_wait.lock
 
 #ifdef CONFIG_PROVE_RCU
-bool __rcu_sync_is_idle(struct rcu_sync *rsp)
+void rcu_sync_lockdep_assert(struct rcu_sync *rsp)
 {
-	WARN_ON(!gp_ops[rsp->gp_type].held());
-	return rsp->gp_state == GP_IDLE;
+	rcu_lockdep_assert(gp_ops[rsp->gp_type].held(),
+			   "suspicious rcu_sync_is_idle() usage");
 }
 #endif
 
-- 
1.5.5.1


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