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| author |   Lai Jiangshan <laijs@linux.alibaba.com> | 2020-02-15 14:37:26 -0800 |
|---|---|---|
| committer |   Paul E. McKenney <paulmck@kernel.org> | 2020-04-27 11:03:50 -0700 |
| commit | 07b4a930fc44a537efecf73c1fd2b4937f64caaa (patch) | |
| tree | 6fb2c7d8d0b502dbc8b8a74a17235d454e65db2d /kernel/rcu/tree_plugin.h | |
| parent | rcu: Make rcu_read_unlock_special() safe for rq/pi locks (diff) | |
| download | linux-dev-07b4a930fc44a537efecf73c1fd2b4937f64caaa.tar.xz linux-dev-07b4a930fc44a537efecf73c1fd2b4937f64caaa.zip | |
rcu: Don't set nesting depth negative in rcu_preempt_deferred_qs()
Now that RCU flavors have been consolidated, an RCU-preempt
rcu_read_unlock() in an interrupt or softirq handler cannot possibly
end the RCU read-side critical section. Consider the old vulnerability
involving rcu_preempt_deferred_qs() being invoked within such a handler
that interrupted an extended RCU read-side critical section, in which
a wakeup might be invoked with a scheduler lock held. Because
rcu_read_unlock_special() no longer does wakeups in such situations,
it is no longer necessary for rcu_preempt_deferred_qs() to set the
nesting level negative.
This commit therefore removes this recursion-protection code from
rcu_preempt_deferred_qs().
[ paulmck: Fix typo in commit log per Steve Rostedt. ]
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/rcu/tree_plugin.h')
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 5 |
1 files changed, 0 insertions, 5 deletions
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index ccad77639d80..263c766b9dc1 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -569,16 +569,11 @@ static bool rcu_preempt_need_deferred_qs(struct task_struct *t) static void rcu_preempt_deferred_qs(struct task_struct *t) { unsigned long flags; - bool couldrecurse = rcu_preempt_depth() >= 0; if (!rcu_preempt_need_deferred_qs(t)) return; - if (couldrecurse) - rcu_preempt_depth_set(rcu_preempt_depth() - RCU_NEST_BIAS); local_irq_save(flags); rcu_preempt_deferred_qs_irqrestore(t, flags); - if (couldrecurse) - rcu_preempt_depth_set(rcu_preempt_depth() + RCU_NEST_BIAS); } /* |