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rcu/nocb: Add a warning for non-GP kthread running GP code 

This commit increases RCU's ability to defend itself by emitting a warning
if one of the nocb CB kthreads invokes the GP kthread's wait function.
This warning augments a similar check that is carried out at the end
of rcutorture testing and when RCU CPU stall warnings are emitted.
The problem with those checks is that the miscreants have long since
departed and disposed of any and all evidence.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2020-08-05 10:35:16 -07:00
parent c0f97f20e5
commit 4569c5ee95
1 changed files with 1 additions and 0 deletions
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1
kernel/rcu/tree_plugin.h
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@ -1926,6 +1926,7 @@ static void nocb_gp_wait(struct rcu_data *my_rdp)
* nearest grace period (if any) to wait for next. The CB kthreads
* and the global grace-period kthread are awakened if needed.
*/
WARN_ON_ONCE(my_rdp->nocb_gp_rdp != my_rdp);
for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_cb_rdp) {
trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("Check"));
rcu_nocb_lock_irqsave(rdp, flags);