e722db8de6
Disabling interrupts and in the RPS case locking input_pkt_queue is split into local_irq_disable() and optional spin_lock(). This breaks on PREEMPT_RT because the spinlock_t typed lock can not be acquired with disabled interrupts. The sections in which the lock is acquired is usually short in a sense that it is not causing long und unbounded latiencies. One exception is the skb_flow_limit() invocation which may invoke a BPF program (and may require sleeping locks). By moving local_irq_disable() + spin_lock() into rps_lock(), we can keep interrupts disabled on !PREEMPT_RT and enabled on PREEMPT_RT kernels. Without RPS on a PREEMPT_RT kernel, the needed synchronisation happens as part of local_bh_disable() on the local CPU. ____napi_schedule() is only invoked if sd is from the local CPU. Replace it with __napi_schedule_irqoff() which already disables interrupts on PREEMPT_RT as needed. Move this call to rps_ipi_queued() and rename the function to napi_schedule_rps as suggested by Jakub. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Reviewed-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
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.