linux-kernel - [PATCH v2 2/2] rcu: Don't dump the stalled CPU on where RCU GP kthread last ran twice

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

Message-ID: <20230712151557.760-3-thunder.leizhen@huawei.com>
Date:   Wed, 12 Jul 2023 23:15:57 +0800
From:   Zhen Lei <thunder.leizhen@...wei.com>
To:     "Paul E . McKenney" <paulmck@...nel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Josh Triplett <josh@...htriplett.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Zqiang <qiang.zhang1211@...il.com>, <rcu@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC:     Zhen Lei <thunder.leizhen@...wei.com>
Subject: [PATCH v2 2/2] rcu: Don't dump the stalled CPU on where RCU GP kthread last ran twice

The stacks of all stalled CPUs will be dumped in rcu_dump_cpu_stacks().
If the CPU on where RCU GP kthread last ran is stalled, its stack does
not need to be dumped again. We can search the corresponding backtrace
based on the printed CPU ID.

For example:
[   87.328275] rcu: rcu_sched kthread starved for ... ->cpu=3  <--------|
... ...                                                                 |
[   89.385007] NMI backtrace for cpu 3                         <--------|
[   89.385179] CPU: 3 PID: 0 Comm: swapper/3 Not tainted 5.10.0+ #22 <--|
[   89.385188] Hardware name: linux,dummy-virt (DT)
[   89.385196] pstate: 60000005 (nZCv daif -PAN -UAO -TCO BTYPE=--)
[   89.385204] pc : arch_cpu_idle+0x40/0xc0
[   89.385211] lr : arch_cpu_idle+0x2c/0xc0
... ...
[   89.385566] Call trace:
[   89.385574]  arch_cpu_idle+0x40/0xc0
[   89.385581]  default_idle_call+0x100/0x450
[   89.385589]  cpuidle_idle_call+0x2f8/0x460
[   89.385596]  do_idle+0x1dc/0x3d0
[   89.385604]  cpu_startup_entry+0x5c/0xb0
[   89.385613]  secondary_start_kernel+0x35c/0x520

Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
Reviewed-by: Joel Fernandes (Google) <joel@...lfernandes.org>
---
 kernel/rcu/tree_stall.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index dcfaa3d5db2cbc7..cc884cd49e026a3 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -534,12 +534,14 @@ static void rcu_check_gp_kthread_starvation(void)
 		       data_race(READ_ONCE(rcu_state.gp_state)),
 		       gpk ? data_race(READ_ONCE(gpk->__state)) : ~0, cpu);
 		if (gpk) {
+			struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
+
 			pr_err("\tUnless %s kthread gets sufficient CPU time, OOM is now expected behavior.\n", rcu_state.name);
 			pr_err("RCU grace-period kthread stack dump:\n");
 			sched_show_task(gpk);
 			if (cpu_is_offline(cpu)) {
 				pr_err("RCU GP kthread last ran on offline CPU %d.\n", cpu);
-			} else  {
+			} else if (!(data_race(READ_ONCE(rdp->mynode->qsmask)) & rdp->grpmask)) {
 				pr_err("Stack dump where RCU GP kthread last ran:\n");
 				dump_cpu_task(cpu);
 			}
-- 
2.25.1