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author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2009-11-02 13:52:29 -0800 |
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committer | Ingo Molnar <mingo@elte.hu> | 2009-11-10 04:12:11 +0100 |
commit | 9160306e6f5b68bb64630c9031c517ca1cf463db (patch) | |
tree | d8f78f99d417f34121c21e45a4675b2b1d5c2674 /kernel/rcutree.h | |
parent | d09b62dfa336447c52a5ec9bb88adbc479b0f3b8 (diff) | |
download | op-kernel-dev-9160306e6f5b68bb64630c9031c517ca1cf463db.zip op-kernel-dev-9160306e6f5b68bb64630c9031c517ca1cf463db.tar.gz |
rcu: Fix note_new_gpnum() uses of ->gpnum
Impose a clear locking design on the note_new_gpnum()
function's use of the ->gpnum counter. This is done by updating
rdp->gpnum only from the corresponding leaf rcu_node structure's
rnp->gpnum field, and even then only under the protection of
that same rcu_node structure's ->lock field. Performance and
scalability are maintained using a form of double-checked
locking, and excessive spinning is avoided by use of the
spin_trylock() function. The use of spin_trylock() is safe due
to the fact that CPUs who fail to acquire this lock will try
again later. The hierarchical nature of the rcu_node data
structure limits contention (which could be limited further if
need be using the RCU_FANOUT kernel parameter).
Without this patch, obscure but quite possible races could
result in a quiescent state that occurred during one grace
period to be accounted to the following grace period, causing
this following grace period to end prematurely. Not good!
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
Cc: <stable@kernel.org> # .32.x
LKML-Reference: <12571987492350-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/rcutree.h')
0 files changed, 0 insertions, 0 deletions