Boqun Feng
55ebfce060
Currently some callsites of sync_rcu_preempt_exp_done() are not called with the corresponding rcu_node's ->lock held, which could introduces bugs as per Paul: o CPU 0 in sync_rcu_preempt_exp_done() reads ->exp_tasks and sees that it is NULL. o CPU 1 blocks within an RCU read-side critical section, so it enqueues the task and points ->exp_tasks at it and clears CPU 1's bit in ->expmask. o All other CPUs clear their bits in ->expmask. o CPU 0 reads ->expmask, sees that it is zero, so incorrectly concludes that all quiescent states have completed, despite the fact that ->exp_tasks is non-NULL. To fix this, sync_rcu_preempt_exp_unlocked() is introduced to replace lockless callsites of sync_rcu_preempt_exp_done(). Further, a lockdep annotation is added into sync_rcu_preempt_exp_done() to prevent mis-use in the future. Signed-off-by: Boqun Feng <boqun.feng@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: Nicholas Piggin <npiggin@gmail.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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.