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[tip/core/rcu,15/47] rcu: Check for callback invocation from offline CPUs

Message ID 1328319922-30828-15-git-send-email-paulmck@linux.vnet.ibm.com
State Accepted
Commit 8146c4e2e2c1972216afece5c50e072e86120e42
Headers show

Commit Message

Paul E. McKenney Feb. 4, 2012, 1:44 a.m. UTC 
From: "Paul E. McKenney" <paul.mckenney@linaro.org>

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@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 kernel/rcutree.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
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Patch

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 575f91d..ac3a810 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.
 	 */
 	local_irq_save(flags);
+	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;