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docs: RCU: Convert lockdep.txt to ReST
- Add a SPDX header;
- Adjust document title;
- Mark literal blocks as such;
- Add it to RCU/index.rst.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
authored by
Mauro Carvalho Chehab
and committed by
Paul E. McKenney
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Documentation/RCU/index.rst
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Documentation/RCU/index.rst
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Documentation/RCU/lockdep.txt
Documentation/RCU/lockdep.rst
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Documentation/RCU/lockdep.txt
Documentation/RCU/lockdep.rst
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.. SPDX-License-Identifier: GPL-2.0
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========================
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RCU and lockdep checking
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========================
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All flavors of RCU have lockdep checking available, so that lockdep is
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aware of when each task enters and leaves any flavor of RCU read-side
···
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deadlocks and the like.
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In addition, RCU provides the following primitives that check lockdep's
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state:
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state::
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rcu_read_lock_held() for normal RCU.
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rcu_read_lock_bh_held() for RCU-bh.
···
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The rcu_dereference_check() check expression can be any boolean
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expression, but would normally include a lockdep expression. However,
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any boolean expression can be used. For a moderately ornate example,
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consider the following:
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consider the following::
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file = rcu_dereference_check(fdt->fd[fd],
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lockdep_is_held(&files->file_lock) ||
···
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any change from taking place, and finally, in case (3) the current task
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is the only task accessing the file_struct, again preventing any change
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from taking place. If the above statement was invoked only from updater
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code, it could instead be written as follows:
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code, it could instead be written as follows::
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file = rcu_dereference_protected(fdt->fd[fd],
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lockdep_is_held(&files->file_lock) ||
···
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For example, the workqueue for_each_pwq() macro is intended to be used
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either within an RCU read-side critical section or with wq->mutex held.
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It is thus implemented as follows:
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It is thus implemented as follows::
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#define for_each_pwq(pwq, wq)
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list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node,