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author | Lai Jiangshan <laijs@cn.fujitsu.com> | 2014-11-18 16:30:01 +0800 |
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committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-01-06 11:02:52 -0800 |
commit | abaf3f9d275b8d856ae5e47531e40c0bfeac012b (patch) | |
tree | 017561fdbffe2f3e840d6af7c5a7bbcf015c70c9 /kernel/rcu/tree.h | |
parent | 3ba4d0e09bf965297e97adf195e0ea246cfe5c74 (diff) | |
download | linux-abaf3f9d275b8d856ae5e47531e40c0bfeac012b.tar.gz |
rcu: Revert "Allow post-unlock reference for rt_mutex" to avoid priority-inversion
The patch dfeb9765ce3c ("Allow post-unlock reference for rt_mutex") ensured rcu-boost safe even the rt_mutex has post-unlock reference. But rt_mutex allowing post-unlock reference is definitely a bug and it was fixed by the commit 27e35715df54 ("rtmutex: Plug slow unlock race"). This fix made the previous patch (dfeb9765ce3c) useless. And even worse, the priority-inversion introduced by the the previous patch still exists. rcu_read_unlock_special() { rt_mutex_unlock(&rnp->boost_mtx); /* Priority-Inversion: * the current task had been deboosted and preempted as a low * priority task immediately, it could wait long before reschedule in, * and the rcu-booster also waits on this low priority task and sleeps. * This priority-inversion makes rcu-booster can't work * as expected. */ complete(&rnp->boost_completion); } Just revert the patch to avoid it. Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcu/tree.h')
-rw-r--r-- | kernel/rcu/tree.h | 5 |
1 files changed, 0 insertions, 5 deletions
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index 883ebc8e2b6e..95356477d560 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -172,11 +172,6 @@ struct rcu_node { /* queued on this rcu_node structure that */ /* are blocking the current grace period, */ /* there can be no such task. */ - struct completion boost_completion; - /* Used to ensure that the rt_mutex used */ - /* to carry out the boosting is fully */ - /* released with no future boostee accesses */ - /* before that rt_mutex is re-initialized. */ struct rt_mutex boost_mtx; /* Used only for the priority-boosting */ /* side effect, not as a lock. */ |