linux-kernel - Re: [paulmckrcu:dev.2024.08.05a] [rcuscale] 0b85a3ea0a: WARNING:at_lib/alloc_tag.c:#alloc_tag_module

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Message-ID: <045374c6-d969-48f6-acd7-320031961bb2@paulmck-laptop>
Date: Fri, 9 Aug 2024 06:44:40 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: kernel test robot <oliver.sang@...el.com>
Cc: oe-lkp@...ts.linux.dev, lkp@...el.com, linux-kernel@...r.kernel.org
Subject: Re: [paulmckrcu:dev.2024.08.05a] [rcuscale]  0b85a3ea0a:
 WARNING:at_lib/alloc_tag.c:#alloc_tag_module_unload

On Fri, Aug 09, 2024 at 10:22:08AM +0800, kernel test robot wrote:
> 
> hi, Paul,
> 
> we noticed the issue for dev.2024.07.31a at first, but recently we cannot handle
> the report fast enough so didn't report that to you.
> 
> we also noticed similar commit in dev.2024.08.06a, but didn't finish test so
> far. in order to avoid further delay, just send out this FYI.
> 
> if it's a known issue and has already fixed in dev.2024.08.06a, please just
> ignore. thanks
> 
> 
> Hello,
> 
> kernel test robot noticed "WARNING:at_lib/alloc_tag.c:#alloc_tag_module_unload" on:
> 
> commit: 0b85a3ea0a8e4d8235e858a3aa1dadc3d0cec4e2 ("rcuscale: Dump stacks of stalled rcu_scale_writer() instances")
> https://github.com/paulmckrcu/linux dev.2024.08.05a
> 
> in testcase: rcuscale
> version: 
> with following parameters:
> 
> 	runtime: 300s
> 	scale_type: rcu
> 
> 
> 
> compiler: clang-18
> test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G
> 
> (please refer to attached dmesg/kmsg for entire log/backtrace)
> 
> 
> +-----------------------------------------------------+------------+------------+
> |                                                     | 532e4ab154 | 0b85a3ea0a |
> +-----------------------------------------------------+------------+------------+
> | WARNING:at_lib/alloc_tag.c:#alloc_tag_module_unload | 0          | 12         |
> | RIP:alloc_tag_module_unload                         | 0          | 12         |
> +-----------------------------------------------------+------------+------------+
> 
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@...el.com>
> | Closes: https://lore.kernel.org/oe-lkp/202408091019.8ed98238-lkp@intel.com
> 
> 
> [  465.251143][ T1160] ------------[ cut here ]------------
> [  465.252395][ T1160] kernel/rcu/rcuscale.c:1037 module rcuscale func:rcu_scale_init has 32 allocated at module unload
> [ 465.252492][ T1160] WARNING: CPU: 0 PID: 1160 at lib/alloc_tag.c:170 alloc_tag_module_unload (lib/alloc_tag.c:168) 
> [  465.256072][ T1160] Modules linked in: rcuscale(-) torture ipmi_devintf ppdev crct10dif_pclmul crc32_pclmul parport_pc aesni_intel parport serio_raw loop fuse [last unloaded: rcuscale]

Good catch, thank you!

Does the diff shown below help?

							Thanx, Paul

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

diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
index b1c50df142eba..6d37596deb1f1 100644
--- a/kernel/rcu/rcuscale.c
+++ b/kernel/rcu/rcuscale.c
@@ -1052,6 +1052,8 @@ rcu_scale_cleanup(void)
 		writer_durations = NULL;
 		kfree(writer_n_durations);
 		writer_n_durations = NULL;
+		kfree(writer_done);
+		writer_done = NULL;
 		kfree(writer_freelists);
 		writer_freelists = NULL;
 	}