From: Paul E. McKenney Date: Fri, 2 Aug 2024 00:43:01 +0000 (-0700) Subject: rcu: Mark callbacks not currently participating in barrier operation X-Git-Tag: v6.12-rc1~166^2^6~8 X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=0616f7e981968743edb1ef758ba1a0e984240419;p=linux-2.6-block.git rcu: Mark callbacks not currently participating in barrier operation 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" Signed-off-by: Neeraj Upadhyay --- 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); } }