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eede42c945
When calling spidev_message() from the one of the ioctl() callbacks, the
spi_lock is already taken. When we then end up calling spidev_sync(), we
get the following splat:
[ 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
Fix it by introducing an unlocked variant of spidev_sync() and calling it
from spidev_message() while other users who don't check the spidev->spi's
existence keep on using the locking flavor.
Reported-by: Francesco Dolcini <francesco@dolcini.it>
Fixes:
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
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https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.