In CONFIG_PREEMPT=y kernels, cond_resched() is a complete no-op, and
thus cannot help advance Tasks-RCU grace periods. However, such grace
periods are only an issue in non-production benchmarking runs of the
Linux kernel. This commit therefore makes cond_resched() invoke
rcu_note_voluntary_context_switch() for kernels implementing Tasks RCU
even in CONFIG_PREEMPT=y kernels.
Reported-by: Steven Rostedt <rost...@goodmis.org>
Signed-off-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
---
include/linux/sched.h | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index b3d697f3b573..fe8f7178a22d 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1617,6 +1617,12 @@ static inline int test_tsk_need_resched(struct
task_struct *tsk)
*/
#ifndef CONFIG_PREEMPT
extern int _cond_resched(void);
+#elif defined(CONFIG_TRACEPOINT_BENCHMARK)
+static inline int _cond_resched(void)
+{
+ rcu_note_voluntary_context_switch(current);
+ return 0;
+}
#else
static inline int _cond_resched(void) { return 0; }
#endif
--
2.5.2
