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author | Paul E. McKenney <paulmck@kernel.org> | 2021-04-16 16:53:16 -0700 |
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committer | Paul E. McKenney <paulmck@kernel.org> | 2021-05-10 16:22:54 -0700 |
commit | 3d3a0d1b508dcc47e82b0e12cde6585bc088b0cc (patch) | |
tree | c186d317780c59edad911127324db8d506112842 /kernel | |
parent | 2f20de99a63b0de9bcceedafc3281e65fbf7d4fd (diff) | |
download | linux-stable-3d3a0d1b508dcc47e82b0e12cde6585bc088b0cc.tar.gz linux-stable-3d3a0d1b508dcc47e82b0e12cde6585bc088b0cc.tar.bz2 linux-stable-3d3a0d1b508dcc47e82b0e12cde6585bc088b0cc.zip |
rcu: Point to documentation of ordering guarantees
Add comments to synchronize_rcu() and friends that point to
Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.rst.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/rcu/srcutree.c | 3 | ||||
-rw-r--r-- | kernel/rcu/tree.c | 20 |
2 files changed, 21 insertions, 2 deletions
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index e26547b34ad3..f8340c3b1c00 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -1000,6 +1000,9 @@ EXPORT_SYMBOL_GPL(synchronize_srcu_expedited); * synchronize_srcu(), srcu_read_lock(), and srcu_read_unlock() are * passed the same srcu_struct structure. * + * Implementation of these memory-ordering guarantees is similar to + * that of synchronize_rcu(). + * * If SRCU is likely idle, expedite the first request. This semantic * was provided by Classic SRCU, and is relied upon by its users, so TREE * SRCU must also provide it. Note that detecting idleness is heuristic diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 6eb64e44bdcd..2437960a2795 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3084,6 +3084,9 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func) * between the call to call_rcu() and the invocation of "func()" -- even * if CPU A and CPU B are the same CPU (but again only if the system has * more than one CPU). + * + * Implementation of these memory-ordering guarantees is described here: + * Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.rst. */ void call_rcu(struct rcu_head *head, rcu_callback_t func) { @@ -3751,6 +3754,9 @@ static int rcu_blocking_is_gp(void) * to have executed a full memory barrier during the execution of * synchronize_rcu() -- even if CPU A and CPU B are the same CPU (but * again only if the system has more than one CPU). + * + * Implementation of these memory-ordering guarantees is described here: + * Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.rst. */ void synchronize_rcu(void) { @@ -3821,7 +3827,7 @@ EXPORT_SYMBOL_GPL(start_poll_synchronize_rcu); /** * poll_state_synchronize_rcu - Conditionally wait for an RCU grace period * - * @oldstate: return from call to get_state_synchronize_rcu() or start_poll_synchronize_rcu() + * @oldstate: value from get_state_synchronize_rcu() or start_poll_synchronize_rcu() * * If a full RCU grace period has elapsed since the earlier call from * which oldstate was obtained, return @true, otherwise return @false. @@ -3837,6 +3843,11 @@ EXPORT_SYMBOL_GPL(start_poll_synchronize_rcu); * (many hours even on 32-bit systems) should check them occasionally * and either refresh them or set a flag indicating that the grace period * has completed. + * + * This function provides the same memory-ordering guarantees that + * would be provided by a synchronize_rcu() that was invoked at the call + * to the function that provided @oldstate, and that returned at the end + * of this function. */ bool poll_state_synchronize_rcu(unsigned long oldstate) { @@ -3851,7 +3862,7 @@ EXPORT_SYMBOL_GPL(poll_state_synchronize_rcu); /** * cond_synchronize_rcu - Conditionally wait for an RCU grace period * - * @oldstate: return value from earlier call to get_state_synchronize_rcu() + * @oldstate: value from get_state_synchronize_rcu() or start_poll_synchronize_rcu() * * If a full RCU grace period has elapsed since the earlier call to * get_state_synchronize_rcu() or start_poll_synchronize_rcu(), just return. @@ -3861,6 +3872,11 @@ EXPORT_SYMBOL_GPL(poll_state_synchronize_rcu); * counter wrap is harmless. If the counter wraps, we have waited for * more than 2 billion grace periods (and way more on a 64-bit system!), * so waiting for one additional grace period should be just fine. + * + * This function provides the same memory-ordering guarantees that + * would be provided by a synchronize_rcu() that was invoked at the call + * to the function that provided @oldstate, and that returned at the end + * of this function. */ void cond_synchronize_rcu(unsigned long oldstate) { |