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I got a deadloop report while doing device(ds2482) add/remove test:
[ 162.241881] w1_master_driver w1_bus_master1: Waiting for w1_bus_master1 to become free: refcnt=1.
[ 163.272251] w1_master_driver w1_bus_master1: Waiting for w1_bus_master1 to become free: refcnt=1.
[ 164.296157] w1_master_driver w1_bus_master1: Waiting for w1_bus_master1 to become free: refcnt=1.
...
__w1_remove_master_device() can't return, because the dev->refcnt is not zero.
w1_add_master_device() |
w1_alloc_dev() |
atomic_set(&dev->refcnt, 2) |
kthread_run() |
|__w1_remove_master_device()
| kthread_stop()
// KTHREAD_SHOULD_STOP is set, |
// threadfn(w1_process) won't be |
// called. |
kthread() |
| // refcnt will never be 0, it's deadloop.
| while (atomic_read(&dev->refcnt)) {...}
After calling w1_add_master_device(), w1_process() is not really
invoked, before w1_process() starting, if kthread_stop() is called
in __w1_remove_master_device(), w1_process() will never be called,
the refcnt can not be decreased, then it causes deadloop in remove
function because of non-zero refcnt.
We need to make sure w1_process() is really started, so move the
set refcnt into w1_process() to fix this problem.
Fixes:
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|---|---|---|
| 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
``make pdfdocs``. The formatted documentation can also be read online at:
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.