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Date:   Fri, 3 Nov 2023 14:30:04 +0800
From:   kernel test robot <oliver.sang@intel.com>
To:     Abhinav Singh <singhabhinav9051571833@gmail.com>
CC:     <oe-lkp@lists.linux.dev>, <lkp@intel.com>,
        <linux-kernel@vger.kernel.org>, <akpm@linux-foundation.org>,
        <brauner@kernel.org>, <surenb@google.com>, <mst@redhat.com>,
        <michael.christie@oracle.com>, <mathieu.desnoyers@efficios.com>,
        <mjguzik@gmail.com>, <npiggin@gmail.com>, <shakeelb@google.com>,
        <peterz@infradead.org>,
        <linux-kernel-mentees@lists.linuxfoundation.org>,
        Abhinav Singh <singhabhinav9051571833@gmail.com>,
        <oliver.sang@intel.com>
Subject: Re: [PATCH v3] Fixing directly deferencing a __rcu pointer warning
Message-ID: <202311031320.c3ebc782-oliver.sang@intel.com>
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Hello,

kernel test robot noticed "WARNING:suspicious_RCU_usage" on:

commit: 0c940f3d0d4c41567b1957a4e09ad68bdeee2111 ("[PATCH v3] Fixing directly deferencing a __rcu pointer warning")
url: https://github.com/intel-lab-lkp/linux/commits/Abhinav-Singh/Fixing-directly-deferencing-a-__rcu-pointer-warning/20231029-044918
base: https://git.kernel.org/cgit/linux/kernel/git/akpm/mm.git mm-everything
patch link: https://lore.kernel.org/all/20231028204609.426841-1-singhabhinav9051571833@gmail.com/
patch subject: [PATCH v3] Fixing directly deferencing a __rcu pointer warning

in testcase: boot

compiler: gcc-12
test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G

(please refer to attached dmesg/kmsg for entire log/backtrace)


+--------------------------------------------------------+------------+------------+
|                                                        | 44c9217272 | 0c940f3d0d |
+--------------------------------------------------------+------------+------------+
| WARNING:suspicious_RCU_usage                           | 0          | 8          |
| kernel/fork.c:#suspicious_rcu_dereference_check()usage | 0          | 8          |
+--------------------------------------------------------+------------+------------+


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 <oliver.sang@intel.com>
| Closes: https://lore.kernel.org/oe-lkp/202311031320.c3ebc782-oliver.sang@intel.com


[    2.386253][    T0] WARNING: suspicious RCU usage
[    2.386253][    T0] 6.6.0-rc4-00506-g0c940f3d0d4c #7 Not tainted
[    2.386253][    T0] -----------------------------
[    2.386253][    T0] kernel/fork.c:2688 suspicious rcu_dereference_check() usage!
[    2.386253][    T0]
[    2.386253][    T0] other info that might help us debug this:
[    2.386253][    T0]
[    2.386253][    T0] rcu_scheduler_active = 2, debug_locks = 1
[    2.386253][    T0] 3 locks held by swapper/0:
[ 2.386253][ T0] #0: ffffffff84dbdc50 (cgroup_threadgroup_rwsem){.+.+}-{0:0}, at: cgroup_can_fork (kbuild/src/rand-x86_64-3/kernel/cgroup/cgroup.c:6538) 
[ 2.386253][ T0] #1: ffffffff8482f010 (tasklist_lock){....}-{2:2}, at: copy_process (kbuild/src/rand-x86_64-3/kernel/fork.c:2624) 
[ 2.386253][ T0] #2: ffffffff84846178 (init_sighand.siglock){....}-{2:2}, at: copy_process (kbuild/src/rand-x86_64-3/kernel/fork.c:2226 kbuild/src/rand-x86_64-3/kernel/fork.c:2643) 
[    2.386253][    T0]
[    2.386253][    T0] stack backtrace:
[    2.386253][    T0] CPU: 0 PID: 0 Comm: swapper Not tainted 6.6.0-rc4-00506-g0c940f3d0d4c #7 88a30a6c68427eeed926405592f52ff30544ebdd
[    2.386253][    T0] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
[    2.386253][    T0] Call Trace:
[    2.386253][    T0]  <TASK>
[ 2.386253][ T0] copy_process (kbuild/src/rand-x86_64-3/kernel/fork.c:2688 (discriminator 9)) 
[ 2.386253][ T0] ? pidfd_prepare (kbuild/src/rand-x86_64-3/kernel/fork.c:2245) 
[ 2.386253][ T0] ? acpi_hw_validate_register (kbuild/src/rand-x86_64-3/drivers/acpi/acpica/hwregs.c:196) 
[ 2.386253][ T0] ? proc_register (kbuild/src/rand-x86_64-3/fs/proc/generic.c:383) 
[ 2.386253][ T0] kernel_clone (kbuild/src/rand-x86_64-3/include/linux/random.h:26 kbuild/src/rand-x86_64-3/kernel/fork.c:2903) 
[ 2.386253][ T0] ? acpi_hw_register_read (kbuild/src/rand-x86_64-3/drivers/acpi/acpica/hwregs.c:489) 
[ 2.386253][ T0] ? create_io_thread (kbuild/src/rand-x86_64-3/kernel/fork.c:2862) 
[ 2.386253][ T0] user_mode_thread (kbuild/src/rand-x86_64-3/kernel/fork.c:2971) 
[ 2.386253][ T0] ? kernel_thread (kbuild/src/rand-x86_64-3/kernel/fork.c:2971) 
[ 2.386253][ T0] ? acpi_hw_validate_io_request (kbuild/src/rand-x86_64-3/drivers/acpi/acpica/hwvalid.c:128) 
[ 2.386253][ T0] ? rest_init (kbuild/src/rand-x86_64-3/init/main.c:1429) 
[ 2.386253][ T0] rest_init (kbuild/src/rand-x86_64-3/init/main.c:691) 
[ 2.386253][ T0] arch_call_rest_init+0x13/0x80 
[ 2.386253][ T0] start_kernel (kbuild/src/rand-x86_64-3/init/main.c:992 (discriminator 1)) 
[ 2.386253][ T0] x86_64_start_reservations (kbuild/src/rand-x86_64-3/arch/x86/kernel/head64.c:544) 
[ 2.386253][ T0] x86_64_start_kernel (??:?) 
[ 2.386253][ T0] secondary_startup_64_no_verify (kbuild/src/rand-x86_64-3/arch/x86/kernel/head_64.S:433) 
[    2.386253][    T0]  </TASK>
[    2.386253][    T0]
[    2.386253][    T0] =============================
[    2.386253][    T0] WARNING: suspicious RCU usage
[    2.386253][    T0] 6.6.0-rc4-00506-g0c940f3d0d4c #7 Not tainted
[    2.386253][    T0] -----------------------------
[    2.386253][    T0] kernel/fork.c:2689 suspicious rcu_dereference_check() usage!
[    2.386253][    T0]
[    2.386253][    T0] other info that might help us debug this:
[    2.386253][    T0]
[    2.386253][    T0] rcu_scheduler_active = 2, debug_locks = 1
[    2.386253][    T0] 3 locks held by swapper/0:
[ 2.386253][ T0] #0: ffffffff84dbdc50 (cgroup_threadgroup_rwsem){.+.+}-{0:0}, at: cgroup_can_fork (kbuild/src/rand-x86_64-3/kernel/cgroup/cgroup.c:6538) 
[ 2.386253][ T0] #1: ffffffff8482f010 (tasklist_lock){....}-{2:2}, at: copy_process (kbuild/src/rand-x86_64-3/kernel/fork.c:2624) 
[ 2.386253][ T0] #2: ffffffff84846178 (init_sighand.siglock){....}-{2:2}, at: copy_process (kbuild/src/rand-x86_64-3/kernel/fork.c:2226 kbuild/src/rand-x86_64-3/kernel/fork.c:2643) 
[    2.386253][    T0]
[    2.386253][    T0] stack backtrace:
[    2.386253][    T0] CPU: 0 PID: 0 Comm: swapper Not tainted 6.6.0-rc4-00506-g0c940f3d0d4c #7 88a30a6c68427eeed926405592f52ff30544ebdd
[    2.386253][    T0] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
[    2.386253][    T0] Call Trace:
[    2.386253][    T0]  <TASK>
[ 2.386253][ T0] copy_process (kbuild/src/rand-x86_64-3/kernel/fork.c:2689 (discriminator 9)) 
[ 2.386253][ T0] ? pidfd_prepare (kbuild/src/rand-x86_64-3/kernel/fork.c:2245) 
[ 2.386253][ T0] ? acpi_hw_validate_register (kbuild/src/rand-x86_64-3/drivers/acpi/acpica/hwregs.c:196) 
[ 2.386253][ T0] ? proc_register (kbuild/src/rand-x86_64-3/fs/proc/generic.c:383) 
[ 2.386253][ T0] kernel_clone (kbuild/src/rand-x86_64-3/include/linux/random.h:26 kbuild/src/rand-x86_64-3/kernel/fork.c:2903) 
[ 2.386253][ T0] ? acpi_hw_register_read (kbuild/src/rand-x86_64-3/drivers/acpi/acpica/hwregs.c:489) 
[ 2.386253][ T0] ? create_io_thread (kbuild/src/rand-x86_64-3/kernel/fork.c:2862) 
[ 2.386253][ T0] user_mode_thread (kbuild/src/rand-x86_64-3/kernel/fork.c:2971) 
[ 2.386253][ T0] ? kernel_thread (kbuild/src/rand-x86_64-3/kernel/fork.c:2971) 
[ 2.386253][ T0] ? acpi_hw_validate_io_request (kbuild/src/rand-x86_64-3/drivers/acpi/acpica/hwvalid.c:128) 
[ 2.386253][ T0] ? rest_init (kbuild/src/rand-x86_64-3/init/main.c:1429) 
[ 2.386253][ T0] rest_init (kbuild/src/rand-x86_64-3/init/main.c:691) 
[ 2.386253][ T0] arch_call_rest_init+0x13/0x80 
[ 2.386253][ T0] start_kernel (kbuild/src/rand-x86_64-3/init/main.c:992 (discriminator 1)) 
[ 2.386253][ T0] x86_64_start_reservations (kbuild/src/rand-x86_64-3/arch/x86/kernel/head64.c:544) 
[ 2.386253][ T0] x86_64_start_kernel (??:?) 
[ 2.386253][ T0] secondary_startup_64_no_verify (kbuild/src/rand-x86_64-3/arch/x86/kernel/head_64.S:433) 
[    2.386253][    T0]  </TASK>
[    2.386253][    T0]
[    2.386253][    T0] =============================
[    2.386253][    T0] WARNING: suspicious RCU usage
[    2.386253][    T0] 6.6.0-rc4-00506-g0c940f3d0d4c #7 Not tainted
[    2.386253][    T0] -----------------------------
[    2.386253][    T0] kernel/fork.c:2690 suspicious rcu_dereference_check() usage!
[    2.386253][    T0]
[    2.386253][    T0] other info that might help us debug this:
[    2.386253][    T0]
[    2.386253][    T0] rcu_scheduler_active = 2, debug_locks = 1
[    2.386253][    T0] 3 locks held by swapper/0:
[ 2.386253][ T0] #0: ffffffff84dbdc50 (cgroup_threadgroup_rwsem){.+.+}-{0:0}, at: cgroup_can_fork (kbuild/src/rand-x86_64-3/kernel/cgroup/cgroup.c:6538) 
[ 2.386253][ T0] #1: ffffffff8482f010 (tasklist_lock){....}-{2:2}, at: copy_process (kbuild/src/rand-x86_64-3/kernel/fork.c:2624) 
[ 2.386253][ T0] #2: ffffffff84846178 (init_sighand.siglock){....}-{2:2}, at: copy_process (kbuild/src/rand-x86_64-3/kernel/fork.c:2226 kbuild/src/rand-x86_64-3/kernel/fork.c:2643) 
[    2.386253][    T0]
[    2.386253][    T0] stack backtrace:
[    2.386253][    T0] CPU: 0 PID: 0 Comm: swapper Not tainted 6.6.0-rc4-00506-g0c940f3d0d4c #7 88a30a6c68427eeed926405592f52ff30544ebdd
[    2.386253][    T0] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
[    2.386253][    T0] Call Trace:
[    2.386253][    T0]  <TASK>
[ 2.386253][ T0] copy_process (kbuild/src/rand-x86_64-3/kernel/fork.c:2690 (discriminator 9)) 
[ 2.386253][ T0] ? pidfd_prepare (kbuild/src/rand-x86_64-3/kernel/fork.c:2245) 
[ 2.386253][ T0] ? acpi_hw_validate_register (kbuild/src/rand-x86_64-3/drivers/acpi/acpica/hwregs.c:196) 
[ 2.386253][ T0] ? proc_register (kbuild/src/rand-x86_64-3/fs/proc/generic.c:383) 
[ 2.386253][ T0] kernel_clone (kbuild/src/rand-x86_64-3/include/linux/random.h:26 kbuild/src/rand-x86_64-3/kernel/fork.c:2903) 
[ 2.386253][ T0] ? acpi_hw_register_read (kbuild/src/rand-x86_64-3/drivers/acpi/acpica/hwregs.c:489) 
[ 2.386253][ T0] ? create_io_thread (kbuild/src/rand-x86_64-3/kernel/fork.c:2862) 
[ 2.386253][ T0] user_mode_thread (kbuild/src/rand-x86_64-3/kernel/fork.c:2971) 
[ 2.386253][ T0] ? kernel_thread (kbuild/src/rand-x86_64-3/kernel/fork.c:2971) 
[ 2.386253][ T0] ? acpi_hw_validate_io_request (kbuild/src/rand-x86_64-3/drivers/acpi/acpica/hwvalid.c:128) 
[ 2.386253][ T0] ? rest_init (kbuild/src/rand-x86_64-3/init/main.c:1429) 
[ 2.386253][ T0] rest_init (kbuild/src/rand-x86_64-3/init/main.c:691) 
[ 2.386253][ T0] arch_call_rest_init+0x13/0x80 
[ 2.386253][ T0] start_kernel (kbuild/src/rand-x86_64-3/init/main.c:992 (discriminator 1)) 
[ 2.386253][ T0] x86_64_start_reservations (kbuild/src/rand-x86_64-3/arch/x86/kernel/head64.c:544) 
[ 2.386253][ T0] x86_64_start_kernel (??:?) 
[ 2.386253][ T0] secondary_startup_64_no_verify (kbuild/src/rand-x86_64-3/arch/x86/kernel/head_64.S:433) 
[    2.386253][    T0]  </TASK>
[    2.387851][    T1] RCU Tasks: Setting shift to 0 and lim to 1 rcu_task_cb_adjust=1.
[    2.389031][    T1] RCU Tasks Rude: Setting shift to 0 and lim to 1 rcu_task_cb_adjust=1.
[    2.390637][    T1] RCU Tasks Trace: Setting shift to 0 and lim to 1 rcu_task_cb_adjust=1.
[    2.391901][    T1] Running RCU-tasks wait API self tests


The kernel config and materials to reproduce are available at:
https://download.01.org/0day-ci/archive/20231103/202311031320.c3ebc782-oliver.sang@intel.com


-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki