ebb37cf3ff
irq_work_raise should not cause a decrementer exception unless it is called from NMI context. Doing so often just results in an immediate masked decrementer interrupt: <...>-550 90d... 4us : update_curr_rt <-dequeue_task_rt <...>-550 90d... 5us : dbs_update_util_handler <-update_curr_rt <...>-550 90d... 6us : arch_irq_work_raise <-irq_work_queue <...>-550 90d... 7us : soft_nmi_interrupt <-soft_nmi_common <...>-550 90d... 7us : printk_nmi_enter <-soft_nmi_interrupt <...>-550 90d.Z. 8us : rcu_nmi_enter <-soft_nmi_interrupt <...>-550 90d.Z. 9us : rcu_nmi_exit <-soft_nmi_interrupt <...>-550 90d... 9us : printk_nmi_exit <-soft_nmi_interrupt <...>-550 90d... 10us : cpuacct_charge <-update_curr_rt The soft_nmi_interrupt here is the call into the watchdog, due to the decrementer interrupt firing with irqs soft-disabled. This is harmless, but sub-optimal. When it's not called from NMI context or with interrupts enabled, mark the decrementer pending in the irq_happened mask directly, rather than having the masked decrementer interupt handler do it. This will be replayed at the next local_irq_enable. See the comment for details. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
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.