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tmp_suning_uos_patched/kernel/rcu
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Lai Jiangshan abaf3f9d27 rcu: Revert "Allow post-unlock reference for rt_mutex" to avoid priority-inversion 
The patch dfeb9765ce ("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 27e35715df ("rtmutex: Plug slow unlock race").
This fix made the previous patch (dfeb9765ce) 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>
2015-01-06 11:02:52 -08:00
..
Makefile rcu: Remove redundant TREE_PREEMPT_RCU config option 2014-10-29 10:20:05 -07:00
rcu.h rcutorture: Add early boot self tests 2014-11-03 19:26:37 -08:00
rcutorture.c rcutorture: Fix rcu_torture_cbflood() memory leak 2014-11-03 19:26:41 -08:00
srcu.c rcu: Eliminate read-modify-write ACCESS_ONCE() calls 2014-07-09 09:14:49 -07:00
tiny_plugin.h rcu: Protect uses of ->jiffies_stall with ACCESS_ONCE() 2014-04-29 08:44:41 -07:00
tiny.c Merge branches 'torture.2014.11.03a', 'cpu.2014.11.03a', 'doc.2014.11.13a', 'fixes.2014.11.13a', 'signal.2014.10.29a' and 'rt.2014.10.29a' into HEAD 2014-11-13 10:39:04 -08:00
tree_plugin.h rcu: Revert "Allow post-unlock reference for rt_mutex" to avoid priority-inversion 2015-01-06 11:02:52 -08:00
tree_trace.c rcu: Stop tracking FSF's postal address 2014-02-17 15:01:37 -08:00
tree.c rcu: Note quiescent state when CPU goes offline 2015-01-06 11:02:51 -08:00
tree.h rcu: Revert "Allow post-unlock reference for rt_mutex" to avoid priority-inversion 2015-01-06 11:02:52 -08:00
update.c Merge branches 'torture.2014.11.03a', 'cpu.2014.11.03a', 'doc.2014.11.13a', 'fixes.2014.11.13a', 'signal.2014.10.29a' and 'rt.2014.10.29a' into HEAD 2014-11-13 10:39:04 -08:00