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| author | Oleg Nesterov <oleg@redhat.com> | 2014-09-29 01:44:21 +0400 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2014-11-13 21:35:40 +0300 |
| commit | ce36f2f3eb6613a73bc6f3a5256bde7dd3f95710 (patch) | |
| tree | 7c225c914aabb54c7ce3add5917386f27e67990a /include/linux/rcupdate.h | |
| parent | b6331ae8afe4118884c4b6e14a213758d88422b2 (diff) | |
| download | linux-ce36f2f3eb6613a73bc6f3a5256bde7dd3f95710.tar.xz | |
rcu: More info about potential deadlocks with rcu_read_unlock()
The comment above rcu_read_unlock() explains the potential deadlock
if the caller holds one of the locks taken by rt_mutex_unlock() paths,
but it is not clear from this documentation that any lock which can
be taken from interrupt can lead to deadlock as well and we need to
take rt_mutex_lock() into account too.
The problem is that rt_mutex_lock() takes wait_lock without disabling
irqs, and thus an interrupt taking some LOCK can obviously race with
rcu_read_unlock_special() called with the same LOCK held.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'include/linux/rcupdate.h')
| -rw-r--r-- | include/linux/rcupdate.h | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 36ea3ba5c516..ae6942a84a0d 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -887,7 +887,9 @@ static inline void rcu_read_lock(void) * Unfortunately, this function acquires the scheduler's runqueue and * priority-inheritance spinlocks. This means that deadlock could result * if the caller of rcu_read_unlock() already holds one of these locks or - * any lock that is ever acquired while holding them. + * any lock that is ever acquired while holding them; or any lock which + * can be taken from interrupt context because rcu_boost()->rt_mutex_lock() + * does not disable irqs while taking ->wait_lock. * * That said, RCU readers are never priority boosted unless they were * preempted. Therefore, one way to avoid deadlock is to make sure |