rcu: Permit RCU_NONIDLE() to be used from interrupt context

There is a need to use RCU from interrupt context, but either before
rcu_irq_enter() is called or after rcu_irq_exit() is called.  If the
interrupt occurs from idle, then lockdep-RCU will complain about such
uses, as they appear to be illegal uses of RCU from the idle loop.
In other environments, RCU_NONIDLE() could be used to properly protect
the use of RCU, but RCU_NONIDLE() currently cannot be invoked except
from process context.

This commit therefore modifies RCU_NONIDLE() to permit its use more
globally.

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

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 115ead2b51553d78a523c4e62db3cb4b84866cd0..0fbbd52e01f9c731d19d29f543d71e2c83fadb91 100644 (file)
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -210,14 +210,12 @@ extern void exit_rcu(void);
  * to nest RCU_NONIDLE() wrappers, but the nesting level is currently
  * quite limited.  If deeper nesting is required, it will be necessary
  * to adjust DYNTICK_TASK_NESTING_VALUE accordingly.
- *
- * This macro may be used from process-level code only.
  */
 #define RCU_NONIDLE(a) \
        do { \
-               rcu_idle_exit(); \
+               rcu_irq_enter(); \
                do { a; } while (0); \
-               rcu_idle_enter(); \
+               rcu_irq_exit(); \
        } while (0)
 
 /*

diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
index 31a10f98ad7e654fe8719b58736fa4e9ed5331b0..aee6df828e0924926080520466c6ca1eee9e5352 100644 (file)
--- a/kernel/rcutiny.c
+++ b/kernel/rcutiny.c
@@ -115,6 +115,7 @@ void rcu_irq_exit(void)
        rcu_idle_enter_common(newval);
        local_irq_restore(flags);
 }
+EXPORT_SYMBOL_GPL(rcu_irq_exit);
 
 /* Common code for rcu_idle_exit() and rcu_irq_enter(), see kernel/rcutree.c. */
 static void rcu_idle_exit_common(long long oldval)
@@ -172,6 +173,7 @@ void rcu_irq_enter(void)
        rcu_idle_exit_common(oldval);
        local_irq_restore(flags);
 }
+EXPORT_SYMBOL_GPL(rcu_irq_enter);
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index f280e542e3e9f531df83b03d1e1fce6cf8ebaaa2..96b8aff433a9363a5c7094421caef945972b1b42 100644 (file)
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -447,6 +447,7 @@ void rcu_irq_exit(void)
                rcu_idle_enter_common(rdtp, oldval);
        local_irq_restore(flags);
 }
+EXPORT_SYMBOL_GPL(rcu_irq_exit);
 
 /*
  * rcu_idle_exit_common - inform RCU that current CPU is moving away from idle
@@ -542,6 +543,7 @@ void rcu_irq_enter(void)
                rcu_idle_exit_common(rdtp, oldval);
        local_irq_restore(flags);
 }
+EXPORT_SYMBOL_GPL(rcu_irq_enter);
 
 /**
  * rcu_nmi_enter - inform RCU of entry to NMI context