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| author | Uladzislau Rezki (Sony) <urezki@gmail.com> | 2025-02-27 16:16:13 +0300 |
|---|---|---|
| committer | Boqun Feng <boqun.feng@gmail.com> | 2025-03-05 05:44:29 +0300 |
| commit | 5a562b8b3f5de4c50f4a9da92bfd3f0a6eebf081 (patch) | |
| tree | e821ff64f12cf61906210c2c79a0bef3114ac68e /include/linux | |
| parent | a6cea3954e62bb200834830515b3e85c9db5c238 (diff) | |
| download | linux-5a562b8b3f5de4c50f4a9da92bfd3f0a6eebf081.tar.xz | |
rcu: Use _full() API to debug synchronize_rcu()
Switch for using of get_state_synchronize_rcu_full() and
poll_state_synchronize_rcu_full() pair to debug a normal
synchronize_rcu() call.
Just using "not" full APIs to identify if a grace period is
passed or not might lead to a false-positive kernel splat.
It can happen, because get_state_synchronize_rcu() compresses
both normal and expedited states into one single unsigned long
value, so a poll_state_synchronize_rcu() can miss GP-completion
when synchronize_rcu()/synchronize_rcu_expedited() concurrently
run.
To address this, switch to poll_state_synchronize_rcu_full() and
get_state_synchronize_rcu_full() APIs, which use separate variables
for expedited and normal states.
Reported-by: cheung wall <zzqq0103.hey@gmail.com>
Closes: https://lore.kernel.org/lkml/Z5ikQeVmVdsWQrdD@pc636/T/
Fixes: 988f569ae041 ("rcu: Reduce synchronize_rcu() latency")
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/r/20250227131613.52683-3-urezki@gmail.com
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/rcupdate_wait.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/include/linux/rcupdate_wait.h b/include/linux/rcupdate_wait.h index f9bed3d3f78d..4c92d4291cce 100644 --- a/include/linux/rcupdate_wait.h +++ b/include/linux/rcupdate_wait.h @@ -16,6 +16,9 @@ struct rcu_synchronize { struct rcu_head head; struct completion completion; + + /* This is for debugging. */ + struct rcu_gp_oldstate oldstate; }; void wakeme_after_rcu(struct rcu_head *head); |