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There is an existing lock hierarchy of
&dev->event_lock --> &fasync_struct.fa_lock --> &f->f_owner.lock
from the following call chain:
input_inject_event():
spin_lock_irqsave(&dev->event_lock,...);
input_handle_event():
input_pass_values():
input_to_handler():
evdev_events():
evdev_pass_values():
spin_lock(&client->buffer_lock);
__pass_event():
kill_fasync():
kill_fasync_rcu():
read_lock(&fa->fa_lock);
send_sigio():
read_lock_irqsave(&fown->lock,...);
&dev->event_lock is HARDIRQ-safe, so interrupts have to be disabled
while grabbing &fasync_struct.fa_lock, otherwise we invert the lock
hierarchy. However, since kill_fasync which calls kill_fasync_rcu is
an exported symbol, it may not necessarily be called with interrupts
disabled.
As kill_fasync_rcu may be called with interrupts disabled (for
example, in the call chain above), we replace calls to
read_lock/read_unlock on &fasync_struct.fa_lock in kill_fasync_rcu
with read_lock_irqsave/read_unlock_irqrestore.
Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
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.