rcu: Add lockdep-RCU checks for simple self-deadlock

It is illegal to have a grace period within a same-flavor RCU read-side
critical section, so this commit adds lockdep-RCU checks to splat when
such abuse is encountered.  This commit does not detect more elaborate
RCU deadlock situations.  These situations might be a job for lockdep
enhancements.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
index 977296dca0a41100b1d549a5ee2fc8a3bd9e22c3..8e00d461911ed8e89983ff5518cff5d9154df33e 100644 (file)
--- a/kernel/rcutiny.c
+++ b/kernel/rcutiny.c
@@ -319,6 +319,10 @@ static void rcu_process_callbacks(struct softirq_action *unused)
  */
 void synchronize_sched(void)
 {
+       rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
+                          !lock_is_held(&rcu_lock_map) &&
+                          !lock_is_held(&rcu_sched_lock_map),
+                          "Illegal synchronize_sched() in RCU read-side critical section");
        cond_resched();
 }
 EXPORT_SYMBOL_GPL(synchronize_sched);

diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h
index 9cb1ae4aabdd8bb894ab7ed7160a07cee5ec144f..4b905404a5bdb70966f887e596d0b567a40305e1 100644 (file)
--- a/kernel/rcutiny_plugin.h
+++ b/kernel/rcutiny_plugin.h
@@ -706,6 +706,11 @@ EXPORT_SYMBOL_GPL(call_rcu);
  */
 void synchronize_rcu(void)
 {
+       rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
+                          !lock_is_held(&rcu_lock_map) &&
+                          !lock_is_held(&rcu_sched_lock_map),
+                          "Illegal synchronize_rcu() in RCU read-side critical section");
+
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
        if (!rcu_scheduler_active)
                return;

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 6c4a6722abfd2fc7297da3e93e6789b94edb6de0..3cf713a724c150557473b297d390bdaab7211d77 100644 (file)
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1816,6 +1816,10 @@ EXPORT_SYMBOL_GPL(call_rcu_bh);
  */
 void synchronize_sched(void)
 {
+       rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
+                          !lock_is_held(&rcu_lock_map) &&
+                          !lock_is_held(&rcu_sched_lock_map),
+                          "Illegal synchronize_sched() in RCU-sched read-side critical section");
        if (rcu_blocking_is_gp())
                return;
        wait_rcu_gp(call_rcu_sched);
@@ -1833,6 +1837,10 @@ EXPORT_SYMBOL_GPL(synchronize_sched);
  */
 void synchronize_rcu_bh(void)
 {
+       rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
+                          !lock_is_held(&rcu_lock_map) &&
+                          !lock_is_held(&rcu_sched_lock_map),
+                          "Illegal synchronize_rcu_bh() in RCU-bh read-side critical section");
        if (rcu_blocking_is_gp())
                return;
        wait_rcu_gp(call_rcu_bh);

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 8bb35d73e1f9d210e95fc85ac330ebb3954577af..3680b6b35bf3f27036a2e92ddc950e905b72f20d 100644 (file)
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -688,6 +688,10 @@ EXPORT_SYMBOL_GPL(call_rcu);
  */
 void synchronize_rcu(void)
 {
+       rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
+                          !lock_is_held(&rcu_lock_map) &&
+                          !lock_is_held(&rcu_sched_lock_map),
+                          "Illegal synchronize_rcu() in RCU read-side critical section");
        if (!rcu_scheduler_active)
                return;
        wait_rcu_gp(call_rcu);

diff --git a/kernel/srcu.c b/kernel/srcu.c
index 0febf61e1aa36dc8d82fbe71ac14f14e6b1dff8d..3f99fa0e8ed319273df7fb9a83d5e1eb588e0179 100644 (file)
--- a/kernel/srcu.c
+++ b/kernel/srcu.c
@@ -172,6 +172,12 @@ static void __synchronize_srcu(struct srcu_struct *sp, void (*sync_func)(void))
 {
        int idx;
 
+       rcu_lockdep_assert(!lock_is_held(&sp->dep_map) &&
+                          !lock_is_held(&rcu_bh_lock_map) &&
+                          !lock_is_held(&rcu_lock_map) &&
+                          !lock_is_held(&rcu_sched_lock_map),
+                          "Illegal synchronize_srcu() in same-type SRCU (or RCU) read-side critical section");
+
        idx = sp->completed;
        mutex_lock(&sp->mutex);