Re: [PATCH v3] Fixing directly deferencing a __rcu pointer warning

From: kernel test robot
Date: Fri Nov 03 2023 - 02:30:27 EST

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

[ 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@xxxxxxxxx

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

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