In kernels built with CONFIG_PREEMPT_RT=n, spinlock critical sections
are RCU readers because they disable preemption. However, they are also
RCU readers in CONFIG_PREEMPT_RT=y because the -rt locking primitives
contain rcu_read_lock() and rcu_read_unlock(). Therefore, upgrade
rcu_dereference.rst to document this non-obvious case.
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Closes: https://lore.kernel.org/lkml/CAHk-=whGKvjHCtJ6W4pQ0_h_k9fiFQ8V2GpM=BqYnB2X=SJ+XQ@mail.gmail.com/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
This commit adds discussion of address and data dependencies to the
beginning of rcu_dereference.rst in order to enable readers to more
easily make the connection to the Linux-kernel memory model in general
and to memory-barriers.txt in particular.
Reported-by: Jonas Oberhauser <jonas.oberhauser@huaweicloud.com>
Reported-by: Akira Yokosawa <akiyks@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
This commit updates rcu_dereference.rst to reflect RCU additions and
changes over the past few years
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit updates the rcu_access_pointer() advice, noting that its
return value should not be assigned to a local variable, and also noting
that there is little point in using rcu_access_pointer() within an RCU
read-side critical section.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
"-foo-" does not work as emphasis in ReST markdown.
Use "*foo*" instead.
Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds an explanation of the special cases where READ_ONCE()
may be used in place of a member of the rcu_dereference() family.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This patch converts rcu_dereference.txt to rcu_dereference.rst and
adds it to index.rst
Signed-off-by: Amol Grover <frextrite@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
