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rcu-tasks: Provide rcu_trace_implies_rcu_gp() 

[ Upstream commit e6c86c513f ]

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: Hou Tao <houtao@huaweicloud.com>
Signed-off-by: Paul 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: Alexei Starovoitov <ast@kernel.org>
Stable-dep-of: 8766733641 ("bpf: Defer the free of inner map when necessary")
Signed-off-by: Sasha Levin <sashal@kernel.org>
(cherry picked from commit 1010882619)
Signed-off-by: Robert Kolchmeyer <rkolchmeyer@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Paul E. McKenney 2024-03-11 14:30:21 -07:00 committed by Sasha Levin
parent d909d381c3
commit d8140159a2
2 changed files with 14 additions and 0 deletions
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12
include/linux/rcupdate.h
View File

@ -205,6 +205,18 @@ static inline void exit_tasks_rcu_stop(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
*

2
kernel/rcu/tasks.h
View File

@ -1098,6 +1098,8 @@ 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_reader_checked.
}