52c1d81ee2
Currently, the rcu_node structure's ->cbovlmask field is set in call_rcu() when a given CPU is suffering from callback overload. But if that CPU goes offline, the outgoing CPU's callbacks is migrated to the running CPU, which is likely to overload the running CPU. However, that CPU's bit in its leaf rcu_node structure's ->cbovlmask field remains zero. Initially, this is OK because the outgoing CPU's bit remains set. However, that bit will be cleared at the next end of a grace period, at which time it is quite possible that the running CPU will still be overloaded. If the running CPU invokes call_rcu(), then overload will be checked for and the bit will be set. Except that there is no guarantee that the running CPU will invoke call_rcu(), in which case the next grace period will fail to take the running CPU's overload condition into account. Plus, because the bit is not set, the end of the grace period won't check for overload on this CPU. This commit therefore adds a call to check_cb_ovld_locked() in rcutree_migrate_callbacks() to set the running CPU's ->cbovlmask bit appropriately. Signed-off-by: Zqiang <qiang1.zhang@intel.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Reviewed-by: Neeraj Upadhyay <quic_neeraju@quicinc.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.