Re: [PATCH v3 22/24] gpio: protect the pointer to gpio_chip in gpio_device with SRCU

Bartosz Golaszewski
2024-02-12T21:21:06Z

On Mon, Feb 12, 2024 at 4:11 PM kernel test robot <oliver.sang@intel.com> wrote:
>
>
>
> Hello,
>
> kernel test robot noticed "WARNING:suspicious_RCU_usage" on:
>
> commit: c21131f83abc1f7227e7a6d5311e1df68bfa44e0 ("[PATCH v3 22/24] gpio: protect the pointer to gpio_chip in gpio_device with SRCU")
> url: https://github.com/intel-lab-lkp/linux/commits/Bartosz-Golaszewski/gpio-protect-the-list-of-GPIO-devices-with-SRCU/20240208-180822
> base: https://git.kernel.org/cgit/linux/kernel/git/brgl/linux.git gpio/for-next
> patch link: https://lore.kernel.org/all/20240208095920.8035-23-brgl@bgdev.pl/
> patch subject: [PATCH v3 22/24] gpio: protect the pointer to gpio_chip in gpio_device with SRCU
>
> 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)
>
>
> +-----------------------------------------------------------------+------------+------------+
> | | a3dfc11062 | c21131f83a |
> +-----------------------------------------------------------------+------------+------------+
> | drivers/gpio/gpiolib.c:#suspicious_rcu_dereference_check()usage | 0 | 8 |
> | drivers/gpio/gpiolib.h:#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/202402122234.d85cca9b-lkp@intel.com
>
>
>
> [ 76.432519][ T1] gpiochip_find_base_unlocked: found new base at 512
> [ 76.434591][ T1]
> [ 76.435240][ T1] =============================
> [ 76.436545][ T1] WARNING: suspicious RCU usage
> [ 76.437813][ T1] 6.8.0-rc1-00050-gc21131f83abc #1 Tainted: G N
> [ 76.439873][ T1] -----------------------------
> [ 76.441158][ T1] drivers/gpio/gpiolib.c:219 suspicious rcu_dereference_check() usage!
> [ 76.443364][ T1]
> [ 76.443364][ T1] other info that might help us debug this:
> [ 76.443364][ T1]
> [ 76.446059][ T1]
> [ 76.446059][ T1] rcu_scheduler_active = 2, debug_locks = 1
> [ 76.448217][ T1] 1 lock held by swapper/1:
> [ 76.449412][ T1] #0: ffff88816954f0f0 (&dev->mutex){....}-{3:3}, at: __driver_attach (drivers/base/dd.c:1216)
> [ 76.451938][ T1]
> [ 76.451938][ T1] stack backtrace:
> [ 76.453486][ T1] CPU: 0 PID: 1 Comm: swapper Tainted: G N 6.8.0-rc1-00050-gc21131f83abc #1
> [ 76.456114][ T1] Call Trace:
> [ 76.456936][ T1] <TASK>
> [ 76.457682][ T1] dump_stack_lvl (lib/dump_stack.c:107 (discriminator 1))
> [ 76.458833][ T1] lockdep_rcu_suspicious (include/linux/context_tracking.h:153 kernel/locking/lockdep.c:6713)
> [ 76.460205][ T1] gpiod_to_chip (drivers/gpio/gpiolib.c:219 (discriminator 9))
> [ 76.461346][ T1] gpiod_hog (drivers/gpio/gpiolib.h:243 drivers/gpio/gpiolib.c:4502)
> [ 76.462400][ T1] ? of_find_property (drivers/of/base.c:223)
> [ 76.463671][ T1] of_gpiochip_add_hog (drivers/gpio/gpiolib-of.c:799)
> [ 76.464933][ T1] ? __pfx_of_gpiochip_add_hog (drivers/gpio/gpiolib-of.c:785)
> [ 76.466378][ T1] ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:4360)
> [ 76.467894][ T1] ? lockdep_hardirqs_on (kernel/locking/lockdep.c:4423)
> [ 76.469220][ T1] ? _raw_spin_unlock_irqrestore (arch/x86/include/asm/preempt.h:103 include/linux/spinlock_api_smp.h:152 kernel/locking/spinlock.c:194)
> [ 76.470786][ T1] of_gpiochip_add (drivers/gpio/gpiolib-of.c:828 drivers/gpio/gpiolib-of.c:1143)
> [ 76.472060][ T1] ? fwnode_property_read_int_array (drivers/base/property.c:268 (discriminator 5))
> [ 76.473692][ T1] gpiochip_add_data_with_key (drivers/gpio/gpiolib.c:989)
> [ 76.475271][ T1] ? kasan_save_track (arch/x86/include/asm/current.h:42 mm/kasan/common.c:60 mm/kasan/common.c:70)
> [ 76.476567][ T1] unittest_gpio_probe (drivers/of/unittest.c:1886)
> [ 76.477928][ T1] platform_probe (drivers/base/platform.c:1404)
> [ 76.479162][ T1] really_probe (drivers/base/dd.c:579 drivers/base/dd.c:658)
> [ 76.480403][ T1] __driver_probe_device (drivers/base/dd.c:800)
> [ 76.481791][ T1] driver_probe_device (drivers/base/dd.c:830)
> [ 76.483097][ T1] __driver_attach (drivers/base/dd.c:1217)
> [ 76.484388][ T1] ? __pfx___driver_attach (drivers/base/dd.c:1157)
> [ 76.485805][ T1] bus_for_each_dev (drivers/base/bus.c:367)
> [ 76.487037][ T1] ? lockdep_init_map_type (kernel/locking/lockdep.c:4892)
> [ 76.488477][ T1] ? __pfx_bus_for_each_dev (drivers/base/bus.c:356)
> [ 76.489897][ T1] ? bus_add_driver (drivers/base/bus.c:672)
> [ 76.491195][ T1] bus_add_driver (drivers/base/bus.c:674)
> [ 76.492463][ T1] driver_register (drivers/base/driver.c:246)
> [ 76.493723][ T1] of_unittest_overlay_gpio (drivers/of/unittest.c:1969 (discriminator 4))
> [ 76.495167][ T1] of_unittest_overlay (drivers/of/unittest.c:2189 drivers/of/unittest.c:3217)
> [ 76.496478][ T1] ? __pfx_of_unittest_overlay (drivers/of/unittest.c:3155)
> [ 76.497886][ T1] ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:4360)
> [ 76.499410][ T1] ? lockdep_hardirqs_on (kernel/locking/lockdep.c:4423)
> [ 76.500744][ T1] of_unittest (drivers/of/unittest.c:4129)
> [ 76.501862][ T1] ? __pfx_of_unittest (drivers/of/unittest.c:4080)
> [ 76.503098][ T1] ? add_device_randomness (drivers/char/random.c:918)
> [ 76.504492][ T1] ? __pfx_of_unittest (drivers/of/unittest.c:4080)
> [ 76.505807][ T1] do_one_initcall (init/main.c:1236)
> [ 76.507054][ T1] ? __pfx_do_one_initcall (init/main.c:1227)
> [ 76.508517][ T1] do_initcalls (init/main.c:1297 init/main.c:1314)
> [ 76.509731][ T1] kernel_init_freeable (init/main.c:1555)
> [ 76.511106][ T1] ? __pfx_kernel_init (init/main.c:1433)
> [ 76.512435][ T1] kernel_init (init/main.c:1443)
> [ 76.513566][ T1] ? _raw_spin_unlock_irq (arch/x86/include/asm/preempt.h:103 include/linux/spinlock_api_smp.h:160 kernel/locking/spinlock.c:202)
> [ 76.514947][ T1] ret_from_fork (arch/x86/kernel/process.c:153)
> [ 76.516125][ T1] ? __pfx_kernel_init (init/main.c:1433)
> [ 76.517440][ T1] ret_from_fork_asm (arch/x86/entry/entry_64.S:250)
> [ 76.518731][ T1] </TASK>
> [ 76.519758][ T1]
> [ 76.520477][ T1] =============================
> [ 76.521774][ T1] WARNING: suspicious RCU usage
> [ 76.523076][ T1] 6.8.0-rc1-00050-gc21131f83abc #1 Tainted: G N
> [ 76.525108][ T1] -----------------------------
> [ 76.526429][ T1] drivers/gpio/gpiolib.h:210 suspicious rcu_dereference_check() usage!
> [ 76.528621][ T1]
> [ 76.528621][ T1] other info that might help us debug this:
> [ 76.528621][ T1]
> [ 76.531350][ T1]
> [ 76.531350][ T1] rcu_scheduler_active = 2, debug_locks = 1
> [ 76.533414][ T1] 2 locks held by swapper/1:
> [ 76.534616][ T1] #0: ffff88816954f0f0 (&dev->mutex){....}-{3:3}, at: __driver_attach (drivers/base/dd.c:1216)
> [ 76.537073][ T1] #1: ffff888163afb6d0 (&gdev->srcu){.+.+}-{0:0}, at: gpiod_request_commit (include/linux/srcu.h:116 include/linux/srcu.h:215 drivers/gpio/gpiolib.h:202 drivers/gpio/gpiolib.c:2243)
> [ 76.539703][ T1]
> [ 76.539703][ T1] stack backtrace:
> [ 76.541276][ T1] CPU: 0 PID: 1 Comm: swapper Tainted: G N 6.8.0-rc1-00050-gc21131f83abc #1
> [ 76.543890][ T1] Call Trace:
> [ 76.544767][ T1] <TASK>
> [ 76.545549][ T1] dump_stack_lvl (lib/dump_stack.c:107 (discriminator 1))
> [ 76.546740][ T1] lockdep_rcu_suspicious (include/linux/context_tracking.h:153 kernel/locking/lockdep.c:6713)
> [ 76.548196][ T1] gpiod_request_commit (drivers/gpio/gpiolib.h:202 drivers/gpio/gpiolib.c:2243)
> [ 76.549584][ T1] ? dump_stack_lvl (lib/dump_stack.c:108)
> [ 76.550829][ T1] gpiochip_request_own_desc (drivers/gpio/gpiolib.c:2454)
> [ 76.552354][ T1] gpiod_hog (drivers/gpio/gpiolib.c:4504)
> [ 76.553556][ T1] of_gpiochip_add_hog (drivers/gpio/gpiolib-of.c:799)
> [ 76.554948][ T1] ? __pfx_of_gpiochip_add_hog (drivers/gpio/gpiolib-of.c:785)
> [ 76.556536][ T1] ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:4360)
> [ 76.558176][ T1] ? lockdep_hardirqs_on (kernel/locking/lockdep.c:4423)
> [ 76.559633][ T1] ? _raw_spin_unlock_irqrestore (arch/x86/include/asm/preempt.h:103 include/linux/spinlock_api_smp.h:152 kernel/locking/spinlock.c:194)
> [ 76.561252][ T1] of_gpiochip_add (drivers/gpio/gpiolib-of.c:828 drivers/gpio/gpiolib-of.c:1143)
> [ 76.562584][ T1] ? fwnode_property_read_int_array (drivers/base/property.c:268 (discriminator 5))
> [ 76.564302][ T1] gpiochip_add_data_with_key (drivers/gpio/gpiolib.c:989)
> [ 76.565974][ T1] ? kasan_save_track (arch/x86/include/asm/current.h:42 mm/kasan/common.c:60 mm/kasan/common.c:70)
> [ 76.567328][ T1] unittest_gpio_probe (drivers/of/unittest.c:1886)
> [ 76.568780][ T1] platform_probe (drivers/base/platform.c:1404)
> [ 76.570065][ T1] really_probe (drivers/base/dd.c:579 drivers/base/dd.c:658)
> [ 76.571309][ T1] __driver_probe_device (drivers/base/dd.c:800)
> [ 76.572801][ T1] driver_probe_device (drivers/base/dd.c:830)
> [ 76.574175][ T1] __driver_attach (drivers/base/dd.c:1217)
> [ 76.575513][ T1] ? __pfx___driver_attach (drivers/base/dd.c:1157)
> [ 76.576994][ T1] bus_for_each_dev (drivers/base/bus.c:367)
> [ 76.578331][ T1] ? lockdep_init_map_type (kernel/locking/lockdep.c:4892)
> [ 76.579877][ T1] ? __pfx_bus_for_each_dev (drivers/base/bus.c:356)
> [ 76.581368][ T1] ? bus_add_driver (drivers/base/bus.c:672)
> [ 76.582799][ T1] bus_add_driver (drivers/base/bus.c:674)
> [ 76.584128][ T1] driver_register (drivers/base/driver.c:246)
> [ 76.585452][ T1] of_unittest_overlay_gpio (drivers/of/unittest.c:1969 (discriminator 4))
> [ 76.586969][ T1] of_unittest_overlay (drivers/of/unittest.c:2189 drivers/of/unittest.c:3217)
> [ 76.588400][ T1] ? __pfx_of_unittest_overlay (drivers/of/unittest.c:3155)
> [ 76.589958][ T1] ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:4360)
> [ 76.591624][ T1] ? lockdep_hardirqs_on (kernel/locking/lockdep.c:4423)
> [ 76.593071][ T1] of_unittest (drivers/of/unittest.c:4129)
> [ 76.594323][ T1] ? __pfx_of_unittest (drivers/of/unittest.c:4080)
> [ 76.595700][ T1] ? add_device_randomness (drivers/char/random.c:918)
> [ 76.597164][ T1] ? __pfx_of_unittest (drivers/of/unittest.c:4080)
> [ 76.598482][ T1] do_one_initcall (init/main.c:1236)
> [ 76.599728][ T1] ? __pfx_do_one_initcall (init/main.c:1227)
> [ 76.601163][ T1] do_initcalls (init/main.c:1297 init/main.c:1314)
> [ 76.602389][ T1] kernel_init_freeable (init/main.c:1555)
> [ 76.603810][ T1] ? __pfx_kernel_init (init/main.c:1433)
> [ 76.605101][ T1] kernel_init (init/main.c:1443)
> [ 76.606235][ T1] ? _raw_spin_unlock_irq (arch/x86/include/asm/preempt.h:103 include/linux/spinlock_api_smp.h:160 kernel/locking/spinlock.c:202)
> [ 76.607627][ T1] ret_from_fork (arch/x86/kernel/process.c:153)
> [ 76.608797][ T1] ? __pfx_kernel_init (init/main.c:1433)
> [ 76.610112][ T1] ret_from_fork_asm (arch/x86/entry/entry_64.S:250)
> [ 76.611412][ T1] </TASK>
> [ 76.612591][ T1] general protection fault, probably for non-canonical address 0xdffffc000000002f: 0000 [#1] PREEMPT KASAN PTI
> [ 76.615654][ T1] KASAN: null-ptr-deref in range [0x0000000000000178-0x000000000000017f]
> [ 76.617847][ T1] CPU: 0 PID: 1 Comm: swapper Tainted: G N 6.8.0-rc1-00050-gc21131f83abc #1
> [ 76.620463][ T1] RIP: 0010:check_init_srcu_struct (kernel/rcu/srcutree.c:408)
> [ 76.622072][ T1] Code: 53 48 89 fb 80 3c 02 00 0f 85 fe 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b 6b 38 48 8d bd 78 01 00 00 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 ce 00 00 00 48 8b 85 78 01 00 00 a8 03 75 0b 5b
> All code
> ========
> 0: 53 push %rbx
> 1: 48 89 fb mov %rdi,%rbx
> 4: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1)
> 8: 0f 85 fe 00 00 00 jne 0x10c
> e: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
> 15: fc ff df
> 18: 48 8b 6b 38 mov 0x38(%rbx),%rbp
> 1c: 48 8d bd 78 01 00 00 lea 0x178(%rbp),%rdi
> 23: 48 89 fa mov %rdi,%rdx
> 26: 48 c1 ea 03 shr $0x3,%rdx
> 2a:* 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction
> 2e: 0f 85 ce 00 00 00 jne 0x102
> 34: 48 8b 85 78 01 00 00 mov 0x178(%rbp),%rax
> 3b: a8 03 test $0x3,%al
> 3d: 75 0b jne 0x4a
> 3f: 5b pop %rbx
>
> Code starting with the faulting instruction
> ===========================================
> 0: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1)
> 4: 0f 85 ce 00 00 00 jne 0xd8
> a: 48 8b 85 78 01 00 00 mov 0x178(%rbp),%rax
> 11: a8 03 test $0x3,%al
> 13: 75 0b jne 0x20
> 15: 5b pop %rbx
> [ 76.627183][ T1] RSP: 0018:ffff888103a6f718 EFLAGS: 00010202
> [ 76.628803][ T1] RAX: dffffc0000000000 RBX: ffff88810ee660f8 RCX: 0000000000000000
> [ 76.630879][ T1] RDX: 000000000000002f RSI: ffff88816976b000 RDI: 0000000000000178
> [ 76.632960][ T1] RBP: 0000000000000000 R08: 692d422d656e696c R09: 007475706e692d42
> [ 76.635045][ T1] R10: ffff888103a6f750 R11: ffffffff810b3aef R12: ffff88810ee66130
> [ 76.641151][ T1] R13: ffff888163afb6c0 R14: 0000000000000000 R15: ffff888163afb6d0
> [ 76.643224][ T1] FS: 0000000000000000(0000) GS:ffffffff84cd1000(0000) knlGS:0000000000000000
> [ 76.645563][ T1] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 76.647278][ T1] CR2: 00007fab8f4456f4 CR3: 0000000004cac000 CR4: 00000000000406b0
> [ 76.649355][ T1] Call Trace:
> [ 76.650221][ T1] <TASK>
> [ 76.651020][ T1] ? die_addr (arch/x86/kernel/dumpstack.c:421 arch/x86/kernel/dumpstack.c:460)
> [ 76.652132][ T1] ? exc_general_protection (arch/x86/kernel/traps.c:701 arch/x86/kernel/traps.c:643)
> [ 76.653604][ T1] ? asm_exc_general_protection (arch/x86/include/asm/idtentry.h:564)
> [ 76.655133][ T1] ? ret_from_fork (arch/x86/kernel/process.c:153)
> [ 76.656355][ T1] ? check_init_srcu_struct (kernel/rcu/srcutree.c:408)
> [ 76.657792][ T1] synchronize_srcu (kernel/rcu/srcutree.c:1167 kernel/rcu/srcutree.c:1458)
> [ 76.659048][ T1] gpiod_request_commit (drivers/gpio/gpiolib.c:127 drivers/gpio/gpiolib.c:2273)
> [ 76.660430][ T1] gpiochip_request_own_desc (drivers/gpio/gpiolib.c:2454)
> [ 76.661898][ T1] gpiod_hog (drivers/gpio/gpiolib.c:4504)
> [ 76.663000][ T1] of_gpiochip_add_hog (drivers/gpio/gpiolib-of.c:799)
> [ 76.664334][ T1] ? __pfx_of_gpiochip_add_hog (drivers/gpio/gpiolib-of.c:785)
> [ 76.665830][ T1] ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:4360)
> [ 76.667387][ T1] ? lockdep_hardirqs_on (kernel/locking/lockdep.c:4423)
> [ 76.668763][ T1] ? _raw_spin_unlock_irqrestore (arch/x86/include/asm/preempt.h:103 include/linux/spinlock_api_smp.h:152 kernel/locking/spinlock.c:194)
> [ 76.670279][ T1] of_gpiochip_add (drivers/gpio/gpiolib-of.c:828 drivers/gpio/gpiolib-of.c:1143)
> [ 76.671550][ T1] ? fwnode_property_read_int_array (drivers/base/property.c:268 (discriminator 5))
> [ 76.673171][ T1] gpiochip_add_data_with_key (drivers/gpio/gpiolib.c:989)
> [ 76.674714][ T1] ? kasan_save_track (arch/x86/include/asm/current.h:42 mm/kasan/common.c:60 mm/kasan/common.c:70)
> [ 76.676002][ T1] unittest_gpio_probe (drivers/of/unittest.c:1886)
> [ 76.677340][ T1] platform_probe (drivers/base/platform.c:1404)
> [ 76.678544][ T1] really_probe (drivers/base/dd.c:579 drivers/base/dd.c:658)
> [ 76.679745][ T1] __driver_probe_device (drivers/base/dd.c:800)
> [ 76.681126][ T1] driver_probe_device (drivers/base/dd.c:830)
> [ 76.682411][ T1] __driver_attach (drivers/base/dd.c:1217)
> [ 76.683679][ T1] ? __pfx___driver_attach (drivers/base/dd.c:1157)
> [ 76.685074][ T1] bus_for_each_dev (drivers/base/bus.c:367)
> [ 76.686340][ T1] ? lockdep_init_map_type (kernel/locking/lockdep.c:4892)
> [ 76.687774][ T1] ? __pfx_bus_for_each_dev (drivers/base/bus.c:356)
> [ 76.689176][ T1] ? bus_add_driver (drivers/base/bus.c:672)
> [ 76.690452][ T1] bus_add_driver (drivers/base/bus.c:674)
> [ 76.691691][ T1] driver_register (drivers/base/driver.c:246)
> [ 76.692949][ T1] of_unittest_overlay_gpio (drivers/of/unittest.c:1969 (discriminator 4))
> [ 76.694377][ T1] of_unittest_overlay (drivers/of/unittest.c:2189 drivers/of/unittest.c:3217)
> [ 76.695724][ T1] ? __pfx_of_unittest_overlay (drivers/of/unittest.c:3155)
> [ 76.697198][ T1] ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:4360)
> [ 76.698764][ T1] ? lockdep_hardirqs_on (kernel/locking/lockdep.c:4423)
> [ 76.700151][ T1] of_unittest (drivers/of/unittest.c:4129)
> [ 76.701323][ T1] ? __pfx_of_unittest (drivers/of/unittest.c:4080)
> [ 76.702622][ T1] ? add_device_randomness (drivers/char/random.c:918)
> [ 76.704050][ T1] ? __pfx_of_unittest (drivers/of/unittest.c:4080)
> [ 76.705347][ T1] do_one_initcall (init/main.c:1236)
> [ 76.706572][ T1] ? __pfx_do_one_initcall (init/main.c:1227)
> [ 76.708227][ T1] do_initcalls (init/main.c:1297 init/main.c:1314)
>
>
> The kernel config and materials to reproduce are available at:
> https://download.01.org/0day-ci/archive/20240212/202402122234.d85cca9b-lkp@intel.com
>
>
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki

Paul,

Could you help me out here? It seems that lockdep complains (with
"suspicious RCU usage") whenever an RCU-protected pointer is passed to
rcu_dereference() but is not actually dereferenced later - in which
case switching to rcu_access_pointer() helps. But in the case of the
of_unittests() it also emits the same warning for
gpiod_direction_input() where gdev->chip is fetched with
rcu_dereference() using CLASS(gpio_chip_guard) and later actually
dereferenced by calling guard.gc->...

Any hints as to what I'm doing wrong?

Thanks,
Bartosz