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rcu: Improve RCU-tasks naming and comments

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The naming and comments associated with some RCU-tasks code make
the faulty assumption that context switches due to cond_resched()
are voluntary.  As several people pointed out, this is not the case.
This commit therefore updates function names and comments to better
reflect current reality.

Reported-by: Byungchul Park <byungchul.park@lge.com>
Reported-by: Joel Fernandes <joel@joelfernandes.org>
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2018-05-14 13:52:27 -07:00
parent a7538352da
commit 6f56f714db
4 changed files with 22 additions and 21 deletions
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12
include/linux/rcupdate.h
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@ -158,11 +158,11 @@ static inline void rcu_init_nohz(void) { }
} while (0)
/*
* Note a voluntary context switch for RCU-tasks benefit. This is a
* macro rather than an inline function to avoid #include hell.
* Note a quasi-voluntary context switch for RCU-tasks's benefit.
* This is a macro rather than an inline function to avoid #include hell.
*/
#ifdef CONFIG_TASKS_RCU
#define rcu_note_voluntary_context_switch_lite(t) \
#define rcu_tasks_qs(t) \
do { \
if (READ_ONCE((t)->rcu_tasks_holdout)) \
WRITE_ONCE((t)->rcu_tasks_holdout, false); \
@ -170,14 +170,14 @@ static inline void rcu_init_nohz(void) { }
#define rcu_note_voluntary_context_switch(t) \
do { \
rcu_all_qs(); \
rcu_note_voluntary_context_switch_lite(t); \
rcu_tasks_qs(t); \
} while (0)
void call_rcu_tasks(struct rcu_head *head, rcu_callback_t func);
void synchronize_rcu_tasks(void);
void exit_tasks_rcu_start(void);
void exit_tasks_rcu_finish(void);
#else /* #ifdef CONFIG_TASKS_RCU */
#define rcu_note_voluntary_context_switch_lite(t) do { } while (0)
#define rcu_tasks_qs(t) do { } while (0)
#define rcu_note_voluntary_context_switch(t) rcu_all_qs()
#define call_rcu_tasks call_rcu_sched
#define synchronize_rcu_tasks synchronize_sched
@ -194,7 +194,7 @@ static inline void exit_tasks_rcu_finish(void) { }
*/
#define cond_resched_tasks_rcu_qs() \
do { \
rcu_note_voluntary_context_switch_lite(current); \
rcu_tasks_qs(current); \
cond_resched(); \
} while (0)