diff options
| author | Frederic Weisbecker <frederic@kernel.org> | 2024-05-15 14:53:31 +0200 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2024-06-28 06:44:12 -0700 |
| commit | 55911a9f4287c19bf7ef29aeace14044a6ed88cb (patch) | |
| tree | 3e01d93cddd58afaa7d15e450b97593e12f1c4aa /kernel/rcu | |
| parent | e7a3c8ea6e2509f71150fa13b00da3ef2bbe2387 (diff) | |
rcu: Remove full memory barrier on RCU stall printout
RCU stall printout fetches the EQS state of a CPU with a preceding full
memory barrier. However there is nothing to order this read against at
this debugging stage. It is inherently racy when performed remotely.
Do a plain read instead.
This was the last user of rcu_dynticks_snap().
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tree.c | 10 | ||||
| -rw-r--r-- | kernel/rcu/tree_stall.h | 4 |
2 files changed, 2 insertions, 12 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 57d813781749..100094717bda 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -296,16 +296,6 @@ static void rcu_dynticks_eqs_online(void) } /* - * Snapshot the ->dynticks counter with full ordering so as to allow - * stable comparison of this counter with past and future snapshots. - */ -static int rcu_dynticks_snap(int cpu) -{ - smp_mb(); // Fundamental RCU ordering guarantee. - return ct_dynticks_cpu_acquire(cpu); -} - -/* * Return true if the snapshot returned from rcu_dynticks_snap() * indicates that RCU is in an extended quiescent state. */ diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h index 460efecd077b..4b0e9d7c4c68 100644 --- a/kernel/rcu/tree_stall.h +++ b/kernel/rcu/tree_stall.h @@ -501,7 +501,7 @@ static void print_cpu_stall_info(int cpu) } delta = rcu_seq_ctr(rdp->mynode->gp_seq - rdp->rcu_iw_gp_seq); falsepositive = rcu_is_gp_kthread_starving(NULL) && - rcu_dynticks_in_eqs(rcu_dynticks_snap(cpu)); + rcu_dynticks_in_eqs(ct_dynticks_cpu(cpu)); rcuc_starved = rcu_is_rcuc_kthread_starving(rdp, &j); if (rcuc_starved) // Print signed value, as negative values indicate a probable bug. @@ -515,7 +515,7 @@ static void print_cpu_stall_info(int cpu) rdp->rcu_iw_pending ? (int)min(delta, 9UL) + '0' : "!."[!delta], ticks_value, ticks_title, - rcu_dynticks_snap(cpu) & 0xffff, + ct_dynticks_cpu(cpu) & 0xffff, ct_dynticks_nesting_cpu(cpu), ct_dynticks_nmi_nesting_cpu(cpu), rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu), data_race(rcu_state.n_force_qs) - rcu_state.n_force_qs_gpstart, |