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| author | Paul E. McKenney <paulmck@kernel.org> | 2022-04-14 11:49:58 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2022-07-21 17:41:56 -0700 |
| commit | 7f4535366f8f77b3ddbc79d4ba82df966c5c2aab (patch) | |
| tree | e5d174cc73883600a800d4beef0377388c8dedf5 /kernel/rcu/tiny.c | |
| parent | dd04140531b5d38b77ad9ff7b18117654be5bf5c (diff) | |
| download | lwn-7f4535366f8f77b3ddbc79d4ba82df966c5c2aab.tar.gz lwn-7f4535366f8f77b3ddbc79d4ba82df966c5c2aab.zip | |
rcu: Make Tiny RCU grace periods visible to polled APIs
This commit makes the Tiny RCU implementation of synchronize_rcu()
increment the rcu_ctrlblk.gp_seq counter, thus making both
synchronize_rcu() and synchronize_rcu_expedited() visible to
get_state_synchronize_rcu() and friends.
Link: https://lore.kernel.org/all/20220121142454.1994916-1-bfoster@redhat.com/
Link: https://docs.google.com/document/d/1RNKWW9jQyfjxw2E8dsXVTdvZYh0HnYeSHDKog9jhdN8/edit?usp=sharing
Cc: Brian Foster <bfoster@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Ian Kent <raven@themaw.net>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/rcu/tiny.c')
| -rw-r--r-- | kernel/rcu/tiny.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c index dbee6bea6726..60071817d939 100644 --- a/kernel/rcu/tiny.c +++ b/kernel/rcu/tiny.c @@ -139,8 +139,10 @@ static __latent_entropy void rcu_process_callbacks(struct softirq_action *unused /* * Wait for a grace period to elapse. But it is illegal to invoke * synchronize_rcu() from within an RCU read-side critical section. - * Therefore, any legal call to synchronize_rcu() is a quiescent - * state, and so on a UP system, synchronize_rcu() need do nothing. + * Therefore, any legal call to synchronize_rcu() is a quiescent state, + * and so on a UP system, synchronize_rcu() need do nothing, other than + * let the polled APIs know that another grace period elapsed. + * * (But Lai Jiangshan points out the benefits of doing might_sleep() * to reduce latency.) * @@ -152,6 +154,7 @@ void synchronize_rcu(void) lock_is_held(&rcu_lock_map) || lock_is_held(&rcu_sched_lock_map), "Illegal synchronize_rcu() in RCU read-side critical section"); + WRITE_ONCE(rcu_ctrlblk.gp_seq, rcu_ctrlblk.gp_seq + 2); } EXPORT_SYMBOL_GPL(synchronize_rcu); |