From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: linux-kernel@vger.kernel.org
Cc: mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca,
josh@joshtriplett.org, dvhltc@us.ibm.com, niv@us.ibm.com,
tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org,
Valdis.Kletnieks@vt.edu, dhowells@redhat.com,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: [PATCH RFC tip/core/rcu 14/18] rcu: lockdep check for exiting to user space as RCU reader
Date: Tue, 15 Dec 2009 15:02:37 -0800 [thread overview]
Message-ID: <12609181612244-git-send-email-> (raw)
In-Reply-To: <20091215230213.GA9093@linux.vnet.ibm.com>
From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Proposed for 2.6.34, not for inclusion.
It is illegal to return to user-space execution while running within an
RCU read-side critical section. It turns out that CONFIG_TREE_PREEMPT_RCU
has enough information lying around to detect this, so add the checks
to lockdep (CONFIG_PROVE_LOCKING).
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
include/linux/rcutiny.h | 4 ++++
include/linux/rcutree.h | 1 +
kernel/lockdep.c | 10 ++++++++++
kernel/rcutree_plugin.h | 22 ++++++++++++++++++++++
4 files changed, 37 insertions(+), 0 deletions(-)
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index b524590..c32b16d 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -29,6 +29,10 @@
void rcu_sched_qs(int cpu);
void rcu_bh_qs(int cpu);
+static inline int rcu_read_lock_held(void)
+{
+ return 0;
+}
#define __rcu_read_lock() preempt_disable()
#define __rcu_read_unlock() preempt_enable()
diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index 564a025..8cd4ac1 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -37,6 +37,7 @@ extern void rcu_bh_qs(int cpu);
extern int rcu_needs_cpu(int cpu);
extern void rcu_scheduler_starting(void);
extern int rcu_expedited_torture_stats(char *page);
+extern int rcu_read_lock_held(void);
#ifdef CONFIG_TREE_PREEMPT_RCU
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 9af5672..a912634 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -3799,4 +3799,14 @@ void lockdep_sys_exit(void)
curr->comm, curr->pid);
lockdep_print_held_locks(curr);
}
+ if (unlikely(rcu_read_lock_held())) {
+ if (!debug_locks_off())
+ return;
+ printk("\n================================================\n");
+ printk( "[ BUG: returning to user space as RCU reader! ]\n");
+ printk( "------------------------------------------------\n");
+ printk("%s/%d is leaving the kernel as RCU reader!\n",
+ curr->comm, curr->pid);
+ lockdep_print_held_locks(curr);
+ }
}
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index e77cdf3..f6258ae 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -310,6 +310,18 @@ void __rcu_read_unlock(void)
}
EXPORT_SYMBOL_GPL(__rcu_read_unlock);
+/*
+ * Return 1 if the current task is provably within an RCU read-side
+ * critical section. The bit about checking a running task to see if
+ * it is blocked is a bit strange, but keep in mind that sleep and
+ * wakeup are not atomic operations.
+ */
+int rcu_read_lock_held(void)
+{
+ return ACCESS_ONCE(current->rcu_read_lock_nesting) != 0 ||
+ (current->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED);
+}
+
#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
/*
@@ -761,6 +773,16 @@ static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags)
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
+/*
+ * Return 1 if the current task is provably within an RCU read-side
+ * critical section. But without preemptible RCU, we never can be
+ * sure, so always return 0.
+ */
+int rcu_read_lock_held(void)
+{
+ return 0;
+}
+
#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
/*
--
1.5.2.5
next prev parent reply other threads:[~2009-12-15 23:14 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-12-15 23:02 [PATCH RFC tip/core/rcu 0/18] rcu: simplify race conditions, add checking Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 01/18] rcu: adjust force_quiescent_state() locking, step 1 Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 02/18] rcu: adjust force_quiescent_state() locking, step 2 Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 03/18] rcu: prohibit starting new grace periods while forcing quiescent states Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 04/18] rcu: eliminate local variable signaled from force_quiescent_state() Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 05/18] rcu: eliminate local variable lastcomp " Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 06/18] rcu: eliminate second argument of rcu_process_dyntick() Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 07/18] rcu: eliminate rcu_process_dyntick() return value Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 08/18] rcu: remove leg of force_quiescent_state() switch statement Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 09/18] rcu: remove redundant grace-period check Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 10/18] rcu: make force_quiescent_state() start grace period if needed Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 11/18] rcu: add force_quiescent_state() testing to rcutorture Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 12/18] rcu: make MAINTAINERS file match new RCU reality Paul E. McKenney
2009-12-16 0:53 ` Josh Triplett
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 13/18] rcu: add debug check for too many rcu_read_unlock() Paul E. McKenney
2009-12-15 23:02 ` Paul E. McKenney [this message]
2009-12-16 10:24 ` [PATCH RFC tip/core/rcu 14/18] rcu: lockdep check for exiting to user space as RCU reader Peter Zijlstra
2009-12-16 15:11 ` Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 15/18] rcu: give different levels of the rcu_node hierarchy distinct lockdep names Paul E. McKenney
2009-12-16 0:59 ` Josh Triplett
2009-12-16 1:59 ` Paul E. McKenney
2009-12-16 10:26 ` Peter Zijlstra
2009-12-16 10:33 ` Peter Zijlstra
2009-12-16 15:13 ` Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 16/18] rcu: make lockdep aware of SRCU read-side critical sections Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 17/18] rcu: Provide different lockdep classes for each flavor of RCU Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 18/18] rcu: add primitives to check for RCU read-side critical sections Paul E. McKenney
2009-12-16 1:04 ` Josh Triplett
2009-12-16 2:08 ` Paul E. McKenney
2009-12-16 10:31 ` Peter Zijlstra
2009-12-16 15:18 ` Paul E. McKenney
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