]> git.karo-electronics.de Git - karo-tx-linux.git/commit
rcu: Fix synchronization for rcu_process_gp_end() uses of ->completed counter
authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Mon, 2 Nov 2009 21:52:28 +0000 (13:52 -0800)
committerGreg Kroah-Hartman <gregkh@suse.de>
Fri, 18 Dec 2009 22:03:00 +0000 (14:03 -0800)
commit1a0d7df3352d775ae3e034b1f2658ea493055a30
tree32a4ce75cdfa07a7f2308b660507d2f21e98e9de
parent1aab3863fee66343b420cb1e5d268c3ee8da27a6
rcu: Fix synchronization for rcu_process_gp_end() uses of ->completed counter

commit d09b62dfa336447c52a5ec9bb88adbc479b0f3b8 upstream.

Impose a clear locking design on the rcu_process_gp_end()
function's use of the ->completed counter.  This is done by
creating a ->completed field in the rcu_node structure, which
can safely be accessed under the protection of that structure's
lock.  Performance and scalability are maintained by using a
form of double-checked locking, so that rcu_process_gp_end()
only acquires the leaf rcu_node structure's ->lock if a grace
period has recently ended.

This fix reduces rcutorture failure rate by at least two orders
of magnitude under heavy stress with force_quiescent_state()
being invoked artificially often.  Without this fix,
unsynchronized access to the ->completed field can cause
rcu_process_gp_end() to advance callbacks whose grace period has
not yet expired.  (Bad idea!)

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <12571987494069-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
kernel/rcutree.c
kernel/rcutree.h