linux-kernel - [PATCH 5/7] Revert "rcu/nocb: Fix rcuog wake-up from offline softirq"

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20250418161542.2429420-6-joelagnelf@nvidia.com>
Date: Fri, 18 Apr 2025 12:15:38 -0400
From: Joel Fernandes <joelagnelf@...dia.com>
To: linux-kernel@...r.kernel.org,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Frederic Weisbecker <frederic@...nel.org>,
	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
	Joel Fernandes <joelagnelf@...dia.com>,
	Josh Triplett <josh@...htriplett.org>,
	Boqun Feng <boqun.feng@...il.com>,
	Uladzislau Rezki <urezki@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Zqiang <qiang.zhang1211@...il.com>
Cc: rcu@...r.kernel.org,
	Usama Arif <usamaarif642@...il.com>
Subject: [PATCH 5/7] Revert "rcu/nocb: Fix rcuog wake-up from offline softirq"

From: Frederic Weisbecker <frederic@...nel.org>

This reverts commit f7345ccc62a4b880cf76458db5f320725f28e400.

swake_up_one_online() has been removed because hrtimers can now assign
a proper online target to hrtimers queued from offline CPUs. Therefore
remove the related hackery.

Link: https://lore.kernel.org/all/20241231170712.149394-4-frederic@kernel.org/
Reviewed-by: Usama Arif <usamaarif642@...il.com>
Reviewed-by: Joel Fernandes <joelagnelf@...dia.com>
Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
Signed-off-by: Joel Fernandes <joelagnelf@...dia.com>
---
 kernel/rcu/tree_nocb.h | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
index 109bc2df1d9a..1596812f7f12 100644
--- a/kernel/rcu/tree_nocb.h
+++ b/kernel/rcu/tree_nocb.h
@@ -554,19 +554,13 @@ static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_alldone,
 			rcu_nocb_unlock(rdp);
 			wake_nocb_gp_defer(rdp, RCU_NOCB_WAKE_LAZY,
 					   TPS("WakeLazy"));
-		} else if (!irqs_disabled_flags(flags) && cpu_online(rdp->cpu)) {
+		} else if (!irqs_disabled_flags(flags)) {
 			/* ... if queue was empty ... */
 			rcu_nocb_unlock(rdp);
 			wake_nocb_gp(rdp, false);
 			trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
 					    TPS("WakeEmpty"));
 		} else {
-			/*
-			 * Don't do the wake-up upfront on fragile paths.
-			 * Also offline CPUs can't call swake_up_one_online() from
-			 * (soft-)IRQs. Rely on the final deferred wake-up from
-			 * rcutree_report_cpu_dead()
-			 */
 			rcu_nocb_unlock(rdp);
 			wake_nocb_gp_defer(rdp, RCU_NOCB_WAKE,
 					   TPS("WakeEmptyIsDeferred"));
-- 
2.43.0