rcu: Improve diagnostics for blocked critical sections in irq
If an RCU read-side critical section occurs within an interrupt handler
or a softirq handler, it cannot have been preempted. Therefore, there is
a check in rcu_read_unlock_special() checking for this error. However,
when this check triggers, it lacks diagnostic information. This commit
therefore moves rcu_read_unlock()'s lockdep annotation to follow the
call to __rcu_read_unlock() and changes rcu_read_unlock_special()'s
WARN_ON_ONCE() to an lockdep_rcu_suspicious() in order to locate where
the offending RCU read-side critical section began. In addition, the
value of the ->rcu_read_unlock_special field is printed.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 3e6afed..70b896e 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -942,9 +942,9 @@
{
rcu_lockdep_assert(rcu_is_watching(),
"rcu_read_unlock() used illegally while idle");
- rcu_lock_release(&rcu_lock_map);
__release(RCU);
__rcu_read_unlock();
+ rcu_lock_release(&rcu_lock_map); /* Keep acq info for rls diags. */
}
/**