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rcu: Improve rcu_note_voluntary_context_switch() reporting 

We expect a quiescent state of TASKS_RCU when cond_resched_tasks_rcu_qs()
is called, no matter whether it actually be scheduled or not. However,
it currently doesn't report the quiescent state when the task enters
into __schedule() as it's called with preempt = true. So make it report
the quiescent state unconditionally when cond_resched_tasks_rcu_qs() is
called.

And in TINY_RCU, even though the quiescent state of rcu_bh also should
be reported when the tick interrupt comes from user, it doesn't. So make
it reported.

Lastly in TREE_RCU, rcu_note_voluntary_context_switch() should be
reported when the tick interrupt comes from not only user but also idle,
as an extended quiescent state.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Simplify rcutiny portion given no RCU-tasks for !PREEMPT. ]
This commit is contained in:
Byungchul Park 2018-05-11 17:30:34 +09:00 committed by Paul E. McKenney
parent 3949fa9bac
commit 07f27570dc
3 changed files with 5 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/linux/rcupdate.h
View File

@ -194,8 +194,8 @@ static inline void exit_tasks_rcu_finish(void) { }
*/ */
#define cond_resched_tasks_rcu_qs() \ #define cond_resched_tasks_rcu_qs() \
do { \ do { \
if (!cond_resched()) \ rcu_note_voluntary_context_switch_lite(current); \
rcu_note_voluntary_context_switch_lite(current); \ cond_resched(); \
} while (0) } while (0)
/* /*

4
kernel/rcu/tiny.c
View File

@ -122,10 +122,8 @@ void rcu_check_callbacks(int user)
{ {
if (user) if (user)
rcu_sched_qs(); rcu_sched_qs();
else if (!in_softirq()) if (user || !in_softirq())
rcu_bh_qs(); rcu_bh_qs();
if (user)
rcu_note_voluntary_context_switch(current);
} }
/* /*

4
kernel/rcu/tree.c
View File

@ -2645,6 +2645,7 @@ void rcu_check_callbacks(int user)
rcu_sched_qs(); rcu_sched_qs();
rcu_bh_qs(); rcu_bh_qs();
rcu_note_voluntary_context_switch(current);
} else if (!in_softirq()) { } else if (!in_softirq()) {
@ -2660,8 +2661,7 @@ void rcu_check_callbacks(int user)
rcu_preempt_check_callbacks(); rcu_preempt_check_callbacks();
if (rcu_pending()) if (rcu_pending())
invoke_rcu_core(); invoke_rcu_core();
if (user)
rcu_note_voluntary_context_switch(current);
trace_rcu_utilization(TPS("End scheduler-tick")); trace_rcu_utilization(TPS("End scheduler-tick"));
} }