diff mbox series

[2/6] rcu: Don't redump the stalled CPU where RCU GP kthread last ran

Message ID 20231019120202.1216228-3-frederic@kernel.org (mailing list archive)
State Mainlined
Commit f3efe02fd56e2498ad8da4c4f444a34aa1456a46
Headers show
Series RCU stall detection updates for v6.7 | expand

Commit Message

Frederic Weisbecker Oct. 19, 2023, 12:01 p.m. UTC 
From: Zhen Lei <thunder.leizhen@huawei.com>

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@huawei.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
 kernel/rcu/tree_stall.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index b5ce0580074e..fc04a8d7ce96 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);
 			}