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Message-Id: <20240816070256.60993-6-neeraj.upadhyay@kernel.org>
Date: Fri, 16 Aug 2024 12:32:48 +0530
From: neeraj.upadhyay@...nel.org
To: rcu@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
kernel-team@...a.com,
rostedt@...dmis.org,
paulmck@...nel.org,
neeraj.upadhyay@...nel.org,
neeraj.upadhyay@....com,
boqun.feng@...il.com,
joel@...lfernandes.org,
urezki@...il.com,
frederic@...nel.org
Subject: [PATCH rcu 06/14] rcu: Mark callbacks not currently participating in barrier operation
From: "Paul E. McKenney" <paulmck@...nel.org>
RCU keeps a count of the number of callbacks that the current
rcu_barrier() is waiting on, but there is currently no easy way to
work out which callback is stuck. One way to do this is to mark idle
RCU-barrier callbacks by making the ->next pointer point to the callback
itself, and this commit does just that.
Later commits will use this for debug output.
Signed-off-by: "Paul E. McKenney" <paulmck@...nel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@...nel.org>
---
kernel/rcu/tree.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index e641cc681901..f931171daecd 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -4403,6 +4403,7 @@ static void rcu_barrier_callback(struct rcu_head *rhp)
{
unsigned long __maybe_unused s = rcu_state.barrier_sequence;
+ rhp->next = rhp; // Mark the callback as having been invoked.
if (atomic_dec_and_test(&rcu_state.barrier_cpu_count)) {
rcu_barrier_trace(TPS("LastCB"), -1, s);
complete(&rcu_state.barrier_completion);
@@ -5424,6 +5425,8 @@ static void __init rcu_init_one(void)
while (i > rnp->grphi)
rnp++;
per_cpu_ptr(&rcu_data, i)->mynode = rnp;
+ per_cpu_ptr(&rcu_data, i)->barrier_head.next =
+ &per_cpu_ptr(&rcu_data, i)->barrier_head;
rcu_boot_init_percpu_data(i);
}
}
--
2.40.1
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