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rcu-tasks: Handle sparse cpu_possible_mask in rcu_tasks_invoke_cbs()

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[ Upstream commit ab2756ea6b ]

If the cpu_possible_mask is sparse (for example, if bits are set only for
CPUs 0, 4, 8, ...), then rcu_tasks_invoke_cbs() will access per-CPU data
for a CPU not in cpu_possible_mask.  It makes these accesses while doing
a workqueue-based binary search for non-empty callback lists.  Although
this search must pass through CPUs not represented in cpu_possible_mask,
it has no need to check the callback list for such CPUs.

This commit therefore changes the rcu_tasks_invoke_cbs() function's
binary search so as to only check callback lists for CPUs present in
cpu_possible_mask.

Reported-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Paul E. McKenney 2022-04-08 09:21:50 -07:00 committed by Greg Kroah-Hartman
parent 230bf5878a
commit 35577eb8bd
1 changed files with 1 additions and 1 deletions
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2
kernel/rcu/tasks.h
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@ -460,7 +460,7 @@ static void rcu_tasks_invoke_cbs(struct rcu_tasks *rtp, struct rcu_tasks_percpu
}
}
if (rcu_segcblist_empty(&rtpcp->cblist))
if (rcu_segcblist_empty(&rtpcp->cblist) || !cpu_possible(cpu))
return;
raw_spin_lock_irqsave_rcu_node(rtpcp, flags);
rcu_segcblist_advance(&rtpcp->cblist, rcu_seq_current(&rtp->tasks_gp_seq));