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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2011-05-24 08:31:09 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2011-09-28 21:36:37 -0700
commitb3fbab0571eb09746cc0283648165ec00efc8eb2 (patch)
tree63bc01cbf03a5df34a96af292a00df4a96dc148a /include/linux
parentd5988af53102f3b73e5e0788be024ccfa51869de (diff)
rcu: Restore checks for blocking in RCU read-side critical sections
Long ago, using TREE_RCU with PREEMPT would result in "scheduling while atomic" diagnostics if you blocked in an RCU read-side critical section. However, PREEMPT now implies TREE_PREEMPT_RCU, which defeats this diagnostic. This commit therefore adds a replacement diagnostic based on PROVE_RCU. Because rcu_lockdep_assert() and lockdep_rcu_dereference() are now being used for things that have nothing to do with rcu_dereference(), rename lockdep_rcu_dereference() to lockdep_rcu_suspicious() and add a third argument that is a string indicating what is suspicious. This third argument is passed in from a new third argument to rcu_lockdep_assert(). Update all calls to rcu_lockdep_assert() to add an informative third argument. Also, add a pair of rcu_lockdep_assert() calls from within rcu_note_context_switch(), one complaining if a context switch occurs in an RCU-bh read-side critical section and another complaining if a context switch occurs in an RCU-sched read-side critical section. These are present only if the PROVE_RCU kernel parameter is enabled. Finally, fix some checkpatch whitespace complaints in lockdep.c. Again, you must enable PROVE_RCU to see these new diagnostics. But you are enabling PROVE_RCU to check out new RCU uses in any case, aren't you? Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/lockdep.h2
-rw-r--r--include/linux/rcupdate.h28
2 files changed, 23 insertions, 7 deletions
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index ef820a3c378..b6a56e37284 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -548,7 +548,7 @@ do { \
#endif
#ifdef CONFIG_PROVE_RCU
-extern void lockdep_rcu_dereference(const char *file, const int line);
+void lockdep_rcu_suspicious(const char *file, const int line, const char *s);
#endif
#endif /* __LINUX_LOCKDEP_H */
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 8f4f881a0ad..8e7470d8b67 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -297,19 +297,31 @@ extern int rcu_my_thread_group_empty(void);
/**
* rcu_lockdep_assert - emit lockdep splat if specified condition not met
* @c: condition to check
+ * @s: informative message
*/
-#define rcu_lockdep_assert(c) \
+#define rcu_lockdep_assert(c, s) \
do { \
static bool __warned; \
if (debug_lockdep_rcu_enabled() && !__warned && !(c)) { \
__warned = true; \
- lockdep_rcu_dereference(__FILE__, __LINE__); \
+ lockdep_rcu_suspicious(__FILE__, __LINE__, s); \
} \
} while (0)
+#define rcu_sleep_check() \
+ do { \
+ rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map), \
+ "Illegal context switch in RCU-bh" \
+ " read-side critical section"); \
+ rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map), \
+ "Illegal context switch in RCU-sched"\
+ " read-side critical section"); \
+ } while (0)
+
#else /* #ifdef CONFIG_PROVE_RCU */
-#define rcu_lockdep_assert(c) do { } while (0)
+#define rcu_lockdep_assert(c, s) do { } while (0)
+#define rcu_sleep_check() do { } while (0)
#endif /* #else #ifdef CONFIG_PROVE_RCU */
@@ -338,14 +350,16 @@ extern int rcu_my_thread_group_empty(void);
#define __rcu_dereference_check(p, c, space) \
({ \
typeof(*p) *_________p1 = (typeof(*p)*__force )ACCESS_ONCE(p); \
- rcu_lockdep_assert(c); \
+ rcu_lockdep_assert(c, "suspicious rcu_dereference_check()" \
+ " usage"); \
rcu_dereference_sparse(p, space); \
smp_read_barrier_depends(); \
((typeof(*p) __force __kernel *)(_________p1)); \
})
#define __rcu_dereference_protected(p, c, space) \
({ \
- rcu_lockdep_assert(c); \
+ rcu_lockdep_assert(c, "suspicious rcu_dereference_protected()" \
+ " usage"); \
rcu_dereference_sparse(p, space); \
((typeof(*p) __force __kernel *)(p)); \
})
@@ -359,7 +373,9 @@ extern int rcu_my_thread_group_empty(void);
#define __rcu_dereference_index_check(p, c) \
({ \
typeof(p) _________p1 = ACCESS_ONCE(p); \
- rcu_lockdep_assert(c); \
+ rcu_lockdep_assert(c, \
+ "suspicious rcu_dereference_index_check()" \
+ " usage"); \
smp_read_barrier_depends(); \
(_________p1); \
})