[PATCH RFC tip/core/rcu 15/41] rcu: Check for callback invocation from offline CPUs

From: Paul E. McKenney
Date: Wed Feb 01 2012 - 14:53:31 EST

From: "Paul E. McKenney" <paul.mckenney@xxxxxxxxxx>

Because quiescent states are now reported from offline CPUs in
CPU_DYING state, there is some possibility that such a CPU might
note the end of a grace period and attempt to start invoking
callbacks. This would be a very bad thing, and is supposed to
be prevented by the fact that the CPU_DYING CPU gets rid of all
its callbacks before reporting the quiescent state. However,
there is other CPU-offline code in the kernel, and it is quite
possible that someone will invoke RCU core processing from that
code. Therefore, this commit adds a warning for this case.

Signed-off-by: Paul E. McKenney <paul.mckenney@xxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
kernel/rcutree.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 9040cb6..03c0d5f 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1373,6 +1373,7 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
* races with call_rcu() from interrupt handlers.
+ WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
bl = rdp->blimit;
trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, bl);
list = rdp->nxtlist;

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