[tip:core/urgent] rcu: Update documentation of rcu_read_unlock()

[tip-bot for Anna-Maria Gleixner <tipbot@zytor.com>]

Commit-ID:  ec84b27f9b3b569f9235413d1945a2006b97b0aa
Gitweb:     https://git.kernel.org/tip/ec84b27f9b3b569f9235413d1945a2006b97b0aa
Author:     Anna-Maria Gleixner <anna-maria@linutronix.de>
AuthorDate: Fri, 25 May 2018 11:05:06 +0200
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sun, 10 Jun 2018 06:14:01 +0200

rcu: Update documentation of rcu_read_unlock()

Since commit b4abf91047cf ("rtmutex: Make wait_lock irq safe") the
explanation in rcu_read_unlock() documentation about irq unsafe rtmutex
wait_lock is no longer valid.

Remove it to prevent kernel developers reading the documentation to rely on
it.

Suggested-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: bigeasy@linutronix.de
Link: https://lkml.kernel.org/r/20180525090507.22248-2-anna-maria@linutronix.de

---
 include/linux/rcupdate.h | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index e679b175b411..65163aa0bb04 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -652,9 +652,7 @@ 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; or any lock which
- * can be taken from interrupt context because rcu_boost()->rt_mutex_lock()
- * does not disable irqs while taking ->wait_lock.
+ * any lock that is ever acquired while holding them.
  *
  * That said, RCU readers are never priority boosted unless they were
  * preempted.  Therefore, one way to avoid deadlock is to make sure