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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>
This commit is contained in:
Paul E. McKenney 2012-07-31 10:12:48 -07:00 committed by Paul E. McKenney
parent 1e3fd2b38c
commit b4270ee356
2 changed files with 4 additions and 4 deletions
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6
include/linux/rcupdate.h
View File

@ -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)
/*

2
kernel/rcutiny.c
View File

@ -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