Plenty of data races at boot with KCSAN-enabled kernel: "BUG: KCSAN: data-race in drm_fbdev_generic_helper_fb_dirty / sys_imageblit" (AMD PRO A12-8830B R7, kernel 6.6.1)
I gave my ThinkPad A275 a test ride with kernel 6.6.1 and KSCSAN enabled. KCSAN_EARLY_ENABLE=y
, KCSAN_STRICT=y
and KCSAN_WEAK_MEMORY=y
were used. dmesg was captured via netconsole.
Until the machine finishes booting and reaches desktop I get 829 data races like this one:
===================================================================
BUG: KCSAN: data-race in drm_fbdev_generic_helper_fb_dirty / sys_imageblit
read to 0xffffa4b6411ebc00 of 7680 bytes by task 66 on cpu 2:
drm_fbdev_generic_helper_fb_dirty+0x325/0x4a0
drm_fb_helper_damage_work+0xfc/0x270
process_scheduled_works+0x3f6/0x650
worker_thread+0x481/0x5c0
kthread+0x212/0x230
ret_from_fork+0x3a/0x50
ret_from_fork_asm+0x11/0x20
write (reordered) to 0xffffa4b6411ec5c4 of 4 bytes by task 438 on cpu 3:
sys_imageblit+0x949/0xca0
drm_fbdev_generic_defio_imageblit+0x23/0x90
bit_putcs+0x2b9/0xad0
fbcon_putcs+0x434/0x4a0
fbcon_redraw+0x1e5/0x280
fbcon_scroll+0x1ac/0x310
con_scroll+0x3ce/0x4d0
vt_console_print+0x444/0x9c0
console_flush_all+0x2e0/0x530
console_unlock+0x71/0x130
do_con_write+0x2a69/0x2aa0
con_write+0x25/0x50
do_output_char+0x31d/0x3a0
n_tty_write+0x5f7/0x780
file_tty_write+0x334/0x520
redirected_tty_write+0x94/0xb0
do_iter_write+0x384/0x550
vfs_writev+0x121/0x210
do_writev+0x9f/0x170
__x64_sys_writev+0x46/0x70
do_syscall_64+0x63/0xa0
entry_SYSCALL_64_after_hwframe+0x4b/0xb5
|
+-> reordered to: sys_imageblit+0x99f/0xca0
Reported by Kernel Concurrency Sanitizer on:
CPU: 3 PID: 438 Comm: ebegin Not tainted 6.6.1-bdver4-dirty #6
Hardware name: LENOVO 20KCS08C0K/20KCS08C0K, BIOS R0NET46W (1.24 ) 04/13/2021
==================================================================
I wanted to get additional data and enabled PROVE_LOCKING=y
in order to enable KCSAN_VERBOSE=y
. But in this case booting stalls/freezes rather early and I get no output via netconsole after that nor can I use the machine.
Some data about the hardware:
System:
Kernel: 6.5.11-gentoo-bdver4 arch: x86_64 bits: 64 Desktop: MATE v: 1.26.1
Distro: Gentoo Base System release 2.14
Machine:
Type: Laptop System: LENOVO product: 20KCS08C0K v: ThinkPad A275
serial: <superuser required>
Mobo: LENOVO model: 20KCS08C0K serial: <superuser required> UEFI: LENOVO
v: R0NET46W (1.24 ) date: 04/13/2021
CPU:
Info: quad core AMD PRO A12-8830B R7 10 COMPUTE CORES 4C+6G [MT MCP]
speed (MHz): avg: 1500 min/max: 1300/2500
Graphics:
Device-1: AMD Wani [Radeon R5/R6/R7 Graphics] driver: amdgpu v: kernel
Display: x11 server: X.Org v: 21.1.9 driver: X: loaded: amdgpu
unloaded: fbdev,modesetting dri: radeonsi gpu: amdgpu
resolution: 1920x1080~60Hz
API: OpenGL v: 4.6 Mesa 23.1.8 renderer: AMD Radeon R7 Graphics (carrizo
LLVM 16.0.6 DRM 3.54 6.5.11-gentoo-bdver4)
Network:
Device-1: Realtek RTL8111/8168/8411 PCI Express Gigabit Ethernet
driver: r8169
Device-2: Realtek RTL8822BE 802.11a/b/g/n/ac WiFi adapter
driver: rtw_8822be
Kernel dmesg and kernel .config attached. dmesg_661-van_bdver4.txt config_661-van_bdver4