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There is a deadlock in rr_close(), which is shown below:
(Thread 1) | (Thread 2)
| rr_open()
rr_close() | add_timer()
spin_lock_irqsave() //(1) | (wait a time)
... | rr_timer()
del_timer_sync() | spin_lock_irqsave() //(2)
(wait timer to stop) | ...
We hold rrpriv->lock in position (1) of thread 1 and
use del_timer_sync() to wait timer to stop, but timer handler
also need rrpriv->lock in position (2) of thread 2.
As a result, rr_close() will block forever.
This patch extracts del_timer_sync() from the protection of
spin_lock_irqsave(), which could let timer handler to obtain
the needed lock.
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Link: https://lore.kernel.org/r/20220417125519.82618-1-duoming@zju.edu.cn
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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.