From b3fbab0571eb09746cc0283648165ec00efc8eb2 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 24 May 2011 08:31:09 -0700 Subject: 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 --- include/linux/rcupdate.h | 28 ++++++++++++++++++++++------ 1 file changed, 22 insertions(+), 6 deletions(-) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 8f4f881a0ad8..8e7470d8b676 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); \ }) -- cgit v1.2.3