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-rw-r--r--include/linux/rcupdate.h23
1 files changed, 17 insertions, 6 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 5f1533e3d032..3bc5de08c0b7 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -45,6 +45,7 @@
#include <linux/bug.h>
#include <linux/compiler.h>
#include <linux/ktime.h>
+#include <linux/irqflags.h>
#include <asm/barrier.h>
@@ -379,12 +380,13 @@ static inline void rcu_init_nohz(void)
* in the inner idle loop.
*
* This macro provides the way out: RCU_NONIDLE(do_something_with_RCU())
- * will tell RCU that it needs to pay attending, invoke its argument
- * (in this example, a call to the do_something_with_RCU() function),
+ * will tell RCU that it needs to pay attention, invoke its argument
+ * (in this example, calling the do_something_with_RCU() function),
* and then tell RCU to go back to ignoring this CPU. It is permissible
- * 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.
+ * to nest RCU_NONIDLE() wrappers, but not indefinitely (but the limit is
+ * on the order of a million or so, even on 32-bit systems). It is
+ * not legal to block within RCU_NONIDLE(), nor is it permissible to
+ * transfer control either into or out of RCU_NONIDLE()'s statement.
*/
#define RCU_NONIDLE(a) \
do { \
@@ -649,7 +651,16 @@ static inline void rcu_preempt_sleep_check(void)
* please be careful when making changes to rcu_assign_pointer() and the
* other macros that it invokes.
*/
-#define rcu_assign_pointer(p, v) smp_store_release(&p, RCU_INITIALIZER(v))
+#define rcu_assign_pointer(p, v) \
+({ \
+ uintptr_t _r_a_p__v = (uintptr_t)(v); \
+ \
+ if (__builtin_constant_p(v) && (_r_a_p__v) == (uintptr_t)NULL) \
+ WRITE_ONCE((p), (typeof(p))(_r_a_p__v)); \
+ else \
+ smp_store_release(&p, RCU_INITIALIZER((typeof(p))_r_a_p__v)); \
+ _r_a_p__v; \
+})
/**
* rcu_access_pointer() - fetch RCU pointer with no dereferencing