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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-01-05 00:09:02 +0100
committerIngo Molnar <mingo@elte.hu>2010-01-13 09:06:02 +0100
commit07079d5357a4d53c2b13126c4a38fb40e6e04966 (patch)
tree1a97552a220a9bbdfceb1cda01c1ee5b92ce75bd /kernel/rcutree.h
parentrcu: Adjust force_quiescent_state() locking, step 2 (diff)
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rcu: Prohibit starting new grace periods while forcing quiescent states
Reduce the number and variety of race conditions by prohibiting the start of a new grace period while force_quiescent_state() is active. A new fqs_active flag in the rcu_state structure is used to trace whether or not force_quiescent_state() is active, and this new flag is tested by rcu_start_gp(). If the CPU that closed out the last grace period needs another grace period, this new grace period may be delayed up to one scheduling-clock tick, but it will eventually get started. 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: <126264655052-git-send-email-> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/rcutree.h')
-rw-r--r--kernel/rcutree.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index d2a0046f63b2..dc386a7c634f 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -277,6 +277,8 @@ struct rcu_state {
u8 signaled ____cacheline_internodealigned_in_smp;
/* Force QS state. */
+ u8 fqs_active; /* force_quiescent_state() */
+ /* is running. */
long gpnum; /* Current gp number. */
long completed; /* # of last completed gp. */