Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit b4270ee3 authored Jul 31, 2012 by Paul E. McKenney Committed by Paul E. McKenney Sep 23, 2012

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.

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

parent 1e3fd2b3

include/linux/rcupdate.h

+2 −4

Original line number	Diff line number	Diff line
		@@ -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)

		/*

kernel/rcutiny.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -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