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authorPaul E. McKenney <paul.mckenney@linaro.org>2012-01-24 00:41:26 +0400
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2012-02-21 21:06:03 +0400
commitc0d6d01bffdce19fa19baad6cb8cc3eed7bfd6f5 (patch)
treeea4c20ddc87b94d7bef2402fe6dbe3186be263c2 /include/linux/rcupdate.h
parent24cd7fd0eaa0d9f5e197ff77a83b006a86696068 (diff)
downloadlinux-c0d6d01bffdce19fa19baad6cb8cc3eed7bfd6f5.tar.xz
rcu: Check for illegal use of RCU from offlined CPUs
Although it is legal to use RCU during early boot, it is anything but legal to use RCU at runtime from an offlined CPU. After all, RCU explicitly ignores offlined CPUs. This commit therefore adds checks for runtime use of RCU from offlined CPUs. These checks are not perfect, in particular, they can be subverted through use of things like rcu_dereference_raw(). Note that it is not possible to put checks in rcu_read_lock() and friends due to the fact that these primitives are used in code that might be used under either RCU or lock-based protection, which means that checking rcu_read_lock() gets you fat piles of false positives. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'include/linux/rcupdate.h')
-rw-r--r--include/linux/rcupdate.h19
1 files changed, 19 insertions, 0 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index f409529ff35a..146d37d31778 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -226,6 +226,15 @@ static inline void destroy_rcu_head_on_stack(struct rcu_head *head)
}
#endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
+#if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU)
+bool rcu_lockdep_current_cpu_online(void);
+#else /* #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */
+static inline bool rcu_lockdep_current_cpu_online(void)
+{
+ return 1;
+}
+#endif /* #else #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */
+
#ifdef CONFIG_DEBUG_LOCK_ALLOC
#ifdef CONFIG_PROVE_RCU
@@ -270,6 +279,9 @@ extern int debug_lockdep_rcu_enabled(void);
* occur in the same context, for example, it is illegal to invoke
* rcu_read_unlock() in process context if the matching rcu_read_lock()
* was invoked from within an irq handler.
+ *
+ * Note that rcu_read_lock() is disallowed if the CPU is either idle or
+ * offline from an RCU perspective, so check for those as well.
*/
static inline int rcu_read_lock_held(void)
{
@@ -277,6 +289,8 @@ static inline int rcu_read_lock_held(void)
return 1;
if (rcu_is_cpu_idle())
return 0;
+ if (!rcu_lockdep_current_cpu_online())
+ return 0;
return lock_is_held(&rcu_lock_map);
}
@@ -313,6 +327,9 @@ extern int rcu_read_lock_bh_held(void);
* notice an extended quiescent state to other CPUs that started a grace
* period. Otherwise we would delay any grace period as long as we run in
* the idle task.
+ *
+ * Similarly, we avoid claiming an SRCU read lock held if the current
+ * CPU is offline.
*/
#ifdef CONFIG_PREEMPT_COUNT
static inline int rcu_read_lock_sched_held(void)
@@ -323,6 +340,8 @@ static inline int rcu_read_lock_sched_held(void)
return 1;
if (rcu_is_cpu_idle())
return 0;
+ if (!rcu_lockdep_current_cpu_online())
+ return 0;
if (debug_locks)
lockdep_opinion = lock_is_held(&rcu_sched_lock_map);
return lockdep_opinion || preempt_count() != 0 || irqs_disabled();