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Message-ID: <20100316000343.GA25857@linux.vnet.ibm.com>
Date: Mon, 15 Mar 2010 17:03:43 -0700
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: linux-kernel@...r.kernel.org
Cc: mingo@...e.hu, laijs@...fujitsu.com, dipankar@...ibm.com,
akpm@...ux-foundation.org, mathieu.desnoyers@...ymtl.ca,
josh@...htriplett.org, dvhltc@...ibm.com, niv@...ibm.com,
tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org,
Valdis.Kletnieks@...edu, dhowells@...hat.com,
eric.dumazet@...il.com, arnd@...db.de
Subject: [PATCH tip/core/rcu] rcu: make rcu_read_lock_bh_held() allow for
disabled BH
Disabling BH can stand in for rcu_read_lock_bh(), and this patch updates
rcu_read_lock_bh_held() to allow for this. In order to avoid include-file
hell, this function is moved out of line to kernel/rcupdate.c.
Reported-by: Arnd Bergmann <arnd@...db.de>
Reported-by: Eric Dumazet <eric.dumazet@...il.com>
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
include/linux/rcupdate.h | 19 ++++---------------
kernel/rcupdate.c | 23 +++++++++++++++++++++++
2 files changed, 27 insertions(+), 15 deletions(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 3024050..e1bdc4b 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -123,22 +123,11 @@ static inline int rcu_read_lock_held(void)
return lock_is_held(&rcu_lock_map);
}
-/**
- * rcu_read_lock_bh_held - might we be in RCU-bh read-side critical section?
- *
- * If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in
- * an RCU-bh read-side critical section. In absence of CONFIG_PROVE_LOCKING,
- * this assumes we are in an RCU-bh read-side critical section unless it can
- * prove otherwise.
- *
- * Check rcu_scheduler_active to prevent false positives during boot.
+/*
+ * rcu_read_lock_bh_held() is defined out of line to avoid #include-file
+ * hell.
*/
-static inline int rcu_read_lock_bh_held(void)
-{
- if (!debug_lockdep_rcu_enabled())
- return 1;
- return lock_is_held(&rcu_bh_lock_map);
-}
+extern int rcu_read_lock_bh_held(void);
/**
* rcu_read_lock_sched_held - might we be in RCU-sched read-side critical section?
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index f1125c1..63fe254 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -45,6 +45,7 @@
#include <linux/mutex.h>
#include <linux/module.h>
#include <linux/kernel_stat.h>
+#include <linux/hardirq.h>
#ifdef CONFIG_DEBUG_LOCK_ALLOC
static struct lock_class_key rcu_lock_key;
@@ -66,6 +67,28 @@ EXPORT_SYMBOL_GPL(rcu_sched_lock_map);
int rcu_scheduler_active __read_mostly;
EXPORT_SYMBOL_GPL(rcu_scheduler_active);
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+
+/**
+ * rcu_read_lock_bh_held - might we be in RCU-bh read-side critical section?
+ *
+ * Check for bottom half being disabled, which covers both the
+ * CONFIG_PROVE_RCU and not cases. Note that if someone uses
+ * rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled)
+ * will show the situation.
+ *
+ * Check debug_lockdep_rcu_enabled() to prevent false positives during boot.
+ */
+int rcu_read_lock_bh_held(void)
+{
+ if (!debug_lockdep_rcu_enabled())
+ return 1;
+ return in_softirq();
+}
+EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
+
+#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+
/*
* This function is invoked towards the end of the scheduler's initialization
* process. Before this is called, the idle task might contain
--
1.6.6
--
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