Date:   Tue, 21 Mar 2023 08:47:51 -0700
From:   Davidlohr Bueso <dave@stgolabs.net>
To:     Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Cc:     paulmck@kernel.org, frederic@kernel.org, jiangshanlai@gmail.com,
        joel@joelfernandes.org, josh@joshtriplett.org,
        linux-kernel@vger.kernel.org, mathieu.desnoyers@efficios.com,
        quic_neeraju@quicinc.com, rcu@vger.kernel.org, rostedt@goodmis.org
Subject: Re: [PATCH v3 2/2] rcu/rcuscale: Stop kfree_scale_thread thread(s)
 after unloading rcuscale
Message-ID: <20230321154751.hgeppd5v327juc36@offworld>
References: <72ba8619-88cb-4bf4-8232-18d8a1b6b5bf@paulmck-laptop>
 <20230321052337.26553-1-qiuxu.zhuo@intel.com>
 <20230321052337.26553-2-qiuxu.zhuo@intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Disposition: inline
In-Reply-To: <20230321052337.26553-2-qiuxu.zhuo@intel.com>
User-Agent: NeoMutt/20220429
Precedence: bulk

On Tue, 21 Mar 2023, Qiuxu Zhuo wrote:

>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@intel.com>

Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>