Re: spidev regression in 6.2-rc kernel

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On 16.01.23 13:06, Francesco Dolcini wrote:
> Hello,
> we spotted a regression on spidev on latest 6.2-rc kernel.
> 
> [  214.047619]
> [  214.049198] ============================================
> [  214.054533] WARNING: possible recursive locking detected
> [  214.059858] 6.2.0-rc3-0.0.0-devel+git.97ec4d559d93 #1 Not tainted
> [  214.065969] --------------------------------------------
> [  214.071290] spidev_test/1454 is trying to acquire lock:
> [  214.076530] c4925dbc (&spidev->spi_lock){+.+.}-{3:3}, at: spidev_ioctl+0x8e0/0xab8
> [  214.084164]
> [  214.084164] but task is already holding lock:
> [  214.090007] c4925dbc (&spidev->spi_lock){+.+.}-{3:3}, at: spidev_ioctl+0x44/0xab8
> [  214.097537]
> [  214.097537] other info that might help us debug this:
> [  214.104075]  Possible unsafe locking scenario:
> [  214.104075]
> [  214.110004]        CPU0
> [  214.112461]        ----
> [  214.114916]   lock(&spidev->spi_lock);
> [  214.118687]   lock(&spidev->spi_lock);
> [  214.122457]
> [  214.122457]  *** DEADLOCK ***
> [  214.122457]
> [  214.128386]  May be due to missing lock nesting notation
> [  214.128386]
> [  214.135183] 2 locks held by spidev_test/1454:
> [  214.139553]  #0: c4925dbc (&spidev->spi_lock){+.+.}-{3:3}, at: spidev_ioctl+0x44/0xab8
> [  214.147524]  #1: c4925e14 (&spidev->buf_lock){+.+.}-{3:3}, at: spidev_ioctl+0x70/0xab8
> [  214.155493]
> [  214.155493] stack backtrace:
> [  214.159861] CPU: 0 PID: 1454 Comm: spidev_test Not tainted 6.2.0-rc3-0.0.0-devel+git.97ec4d559d93 #1
> [  214.169012] Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
> [  214.175555]  unwind_backtrace from show_stack+0x10/0x14
> [  214.180819]  show_stack from dump_stack_lvl+0x60/0x90
> [  214.185900]  dump_stack_lvl from __lock_acquire+0x874/0x2858
> [  214.191584]  __lock_acquire from lock_acquire+0xfc/0x378
> [  214.196918]  lock_acquire from __mutex_lock+0x9c/0x8a8
> [  214.202083]  __mutex_lock from mutex_lock_nested+0x1c/0x24
> [  214.207597]  mutex_lock_nested from spidev_ioctl+0x8e0/0xab8
> [  214.213284]  spidev_ioctl from sys_ioctl+0x4d0/0xe2c
> [  214.218277]  sys_ioctl from ret_fast_syscall+0x0/0x1c
> [  214.223351] Exception stack(0xe75cdfa8 to 0xe75cdff0)
> [  214.228422] dfa0:                   00000000 00001000 00000003 40206b00 bee266e8 bee266e0
> [  214.236617] dfc0: 00000000 00001000 006a71a0 00000036 004c0040 004bfd18 00000000 00000003
> [  214.244809] dfe0: 00000036 bee266c8 b6f16dc5 b6e8e5f6
> 
> 
> This is not running the latest rc4, but on sha 97ec4d559d93 (this is
> just what our CI had available when this test was run). I was not able
> to bisect it, but it seems something that you could have introduced.
> 
> The log is from an apalis-imx6, but I have the same on other ARM SOC.

Thanks for the report. To be sure the issue doesn't fall through the
cracks unnoticed, I'm adding it to regzbot, the Linux kernel regression
tracking bot:

#regzbot ^introduced 1f4d2dd45b6e
#regzbot title spi: spidev: recursive locking error
#regzbot monitor:
https://lore.kernel.org/all/20230116144149.305560-1-brgl@xxxxxxxx/
#regzbot fix: spi: spidev: fix a recursive locking error
#regzbot ignore-activity

This isn't a regression? This issue or a fix for it are already
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Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
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