linux-kernel - [PATCH v3 2/2] rcu/rcuscale: Stop kfree_scale_thread thread(s) after unloading rcuscale

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Date:   Tue, 21 Mar 2023 13:23:37 +0800
From:   Qiuxu Zhuo <qiuxu.zhuo@...el.com>
To:     paulmck@...nel.org
Cc:     dave@...olabs.net, frederic@...nel.org, jiangshanlai@...il.com,
        joel@...lfernandes.org, josh@...htriplett.org,
        linux-kernel@...r.kernel.org, mathieu.desnoyers@...icios.com,
        qiuxu.zhuo@...el.com, quic_neeraju@...cinc.com,
        rcu@...r.kernel.org, rostedt@...dmis.org
Subject: [PATCH v3 2/2] rcu/rcuscale: Stop kfree_scale_thread thread(s) after unloading rcuscale

When running the 'kfree_rcu_test' test case with commands [1] the call
trace [2] was thrown. This was because the kfree_scale_thread thread(s)
still run after unloading rcuscale and torture modules. Fix the call
trace by invoking kfree_scale_cleanup() from rcu_scale_cleanup() when
removing the rcuscale module.

[1] modprobe rcuscale kfree_rcu_test=1
    // After some time
    rmmod rcuscale
    rmmod torture

[2] BUG: unable to handle page fault for address: ffffffffc0601a87
    #PF: supervisor instruction fetch in kernel mode
    #PF: error_code(0x0010) - not-present page
    PGD 11de4f067 P4D 11de4f067 PUD 11de51067 PMD 112f4d067 PTE 0
    Oops: 0010 [#1] PREEMPT SMP NOPTI
    CPU: 1 PID: 1798 Comm: kfree_scale_thr Not tainted 6.3.0-rc1-rcu+ #1
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
    RIP: 0010:0xffffffffc0601a87
    Code: Unable to access opcode bytes at 0xffffffffc0601a5d.
    RSP: 0018:ffffb25bc2e57e18 EFLAGS: 00010297
    RAX: 0000000000000000 RBX: ffffffffc061f0b6 RCX: 0000000000000000
    RDX: 0000000000000000 RSI: ffffffff962fd0de RDI: ffffffff962fd0de
    RBP: ffffb25bc2e57ea8 R08: 0000000000000000 R09: 0000000000000000
    R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000000
    R13: 0000000000000000 R14: 000000000000000a R15: 00000000001c1dbe
    FS:  0000000000000000(0000) GS:ffff921fa2200000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: ffffffffc0601a5d CR3: 000000011de4c006 CR4: 0000000000370ee0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    Call Trace:
     <TASK>
     ? kvfree_call_rcu+0xf0/0x3a0
     ? kthread+0xf3/0x120
     ? kthread_complete_and_exit+0x20/0x20
     ? ret_from_fork+0x1f/0x30
     </TASK>
    Modules linked in: rfkill sunrpc ... [last unloaded: torture]
    CR2: ffffffffc0601a87
    ---[ end trace 0000000000000000 ]---

Fixes: e6e78b004fa7 ("rcuperf: Add kfree_rcu() performance Tests")
Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@...el.com>
---
v1 -> v2:

 - Move rcu_scale_cleanup() after kfree_scale_cleanup() to eliminate the
   declaration of kfree_scale_cleanup().

 - Remove the unnecessary step "modprobe torture" from the commit message.

 - Add the description for why move rcu_scale_cleanup() after
   kfree_scale_cleanup() to the commit message.

v2 -> v3:

 - Split the single v2 patch into two patches.

 - Move the commit message description for why move rcu_scale_cleanup()
   after kfree_scale_cleanup() to Patch 1.

 kernel/rcu/rcuscale.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
index e99096a4f094..5a000d26f03e 100644
--- a/kernel/rcu/rcuscale.c
+++ b/kernel/rcu/rcuscale.c
@@ -797,6 +797,11 @@ rcu_scale_cleanup(void)
 	if (gp_exp && gp_async)
 		SCALEOUT_ERRSTRING("No expedited async GPs, so went with async!");
 
+	if (kfree_rcu_test) {
+		kfree_scale_cleanup();
+		return;
+	}
+
 	if (torture_cleanup_begin())
 		return;
 	if (!cur_ops) {
-- 
2.17.1