Commit e6c86c51 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Alexei Starovoitov
Browse files

rcu-tasks: Provide rcu_trace_implies_rcu_gp() 



As an accident of implementation, an RCU Tasks Trace grace period also
acts as an RCU grace period.  However, this could change at any time.
This commit therefore creates an rcu_trace_implies_rcu_gp() that currently
returns true to codify this accident.  Code relying on this accident
must call this function to verify that this accident is still happening.

Reported-by: default avatarHou Tao <houtao@huaweicloud.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Link: https://lore.kernel.org/r/20221014113946.965131-2-houtao@huaweicloud.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 62c69e89

include/linux/rcupdate.h

+12 −0
Original line number Diff line number Diff line
@@ -240,6 +240,18 @@ static inline void exit_tasks_rcu_start(void) { } 
static inline void exit_tasks_rcu_finish(void) { }

#endif /* #else #ifdef CONFIG_TASKS_RCU_GENERIC */



/**

 * rcu_trace_implies_rcu_gp - does an RCU Tasks Trace grace period imply an RCU grace period?

 *

 * As an accident of implementation, an RCU Tasks Trace grace period also

 * acts as an RCU grace period.  However, this could change at any time.

 * Code relying on this accident must call this function to verify that

 * this accident is still happening.

 *

 * You have been warned!

 */

static inline bool rcu_trace_implies_rcu_gp(void) { return true; }



/**

 * cond_resched_tasks_rcu_qs - Report potential quiescent states to RCU

 *

kernel/rcu/tasks.h

+2 −0
Original line number Diff line number Diff line
@@ -1535,6 +1535,8 @@ static void rcu_tasks_trace_postscan(struct list_head *hop) 
{

	// Wait for late-stage exiting tasks to finish exiting.

	// These might have passed the call to exit_tasks_rcu_finish().



	// If you remove the following line, update rcu_trace_implies_rcu_gp()!!!

	synchronize_rcu();

	// Any tasks that exit after this point will set

	// TRC_NEED_QS_CHECKED in ->trc_reader_special.b.need_qs.