2022-04-22 18:24:26

by Zqiang

Subject: [PATCH] rcu: Put panic_on_rcu_stall() after expedited RCU CPU stall warnings

When the expedited RCU CPU stall warning is treated as panic, if
it's triggered, the stall info should be printed first and tell us
reason, rather than directly panic.

Signed-off-by: Zqiang <[email protected]>
---
kernel/rcu/tree_exp.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
index 571b0a700cce..f05a15b11fa0 100644
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -623,7 +623,6 @@ static void synchronize_rcu_expedited_wait(void)
return;
if (rcu_stall_is_suppressed())
continue;
- panic_on_rcu_stall();
trace_rcu_stall_warning(rcu_state.name, TPS("ExpeditedStall"));
pr_err("INFO: %s detected expedited stalls on CPUs/tasks: {",
rcu_state.name);
@@ -671,6 +670,7 @@ static void synchronize_rcu_expedited_wait(void)
}
}
jiffies_stall = 3 * rcu_exp_jiffies_till_stall_check() + 3;
+ panic_on_rcu_stall();
}
}

--
2.25.1

2022-04-22 21:16:01

by Paul E. McKenney

Subject: Re: [PATCH] rcu: Put panic_on_rcu_stall() after expedited RCU CPU stall warnings

On Fri, Apr 22, 2022 at 09:15:18PM +0800, Zqiang wrote:
> When the expedited RCU CPU stall warning is treated as panic, if
> it's triggered, the stall info should be printed first and tell us
> reason, rather than directly panic.
>
> Signed-off-by: Zqiang <[email protected]>

Good eyes, thank you!

Queued for v5.20, with the wordsmithing shown below. Please let me
know if I messed anything up.

Thanx, Paul

------------------------------------------------------------------------

commit e5215598af9bdf5509c7e7c6f896f50df0cdaf4b
Author: Zqiang <[email protected]>
Date: Fri Apr 22 21:15:18 2022 +0800

rcu: Put panic_on_rcu_stall() after expedited RCU CPU stall warnings

When a normal RCU CPU stall warning is encountered with the
panic_on_rcu_stall sysfs variable is set, the system panics only after
the stall warning is printed. But when an expedited RCU CPU stall
warning is encountered with the panic_on_rcu_stall sysfs variable is
set, the system panics first, thus never printing the stall warning.
This commit therefore brings the expedited stall warning into line with
the normal stall warning by printing first and panicking afterwards.

Signed-off-by: Zqiang <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
index 571b0a700cce..f05a15b11fa0 100644
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -623,7 +623,6 @@ static void synchronize_rcu_expedited_wait(void)
return;
if (rcu_stall_is_suppressed())
continue;
- panic_on_rcu_stall();
trace_rcu_stall_warning(rcu_state.name, TPS("ExpeditedStall"));
pr_err("INFO: %s detected expedited stalls on CPUs/tasks: {",
rcu_state.name);
@@ -671,6 +670,7 @@ static void synchronize_rcu_expedited_wait(void)
}
}
jiffies_stall = 3 * rcu_exp_jiffies_till_stall_check() + 3;
+ panic_on_rcu_stall();
}
}