I'm sorry for the typo in the email address!
Anna-Maria
On Thu, 31 Aug 2017, Anna-Maria Gleixner wrote:
> There are quite some places in the kernel which use a combination of
> hrtimers and tasklets to make use of the precise expiry of hrtimers, which
> schedule a tasklet to bring the actual function into softirq context.
>
> This was introduced when the previous hrtimer softirq code was
> removed. That code was implemented by expiring the timer in hard irq
> context and then deferring the execution of the callback into softirq
> context. That caused a lot of pointless shuffling between the rbtree and a
> linked list.
>
> In recent discussions it turned out that more potential users of hrtimers
> in softirq context might come up. Aside of that the RT patches need this
> functionality as well to defer hrtimers into softirq context if their
> callbacks are not interrupt safe on RT.
>
> This series implements a new approach by adding SOFT_* clock ids and
> instead of doing the list shuffle, timers started with these clock ids are
> put into separate soft expiry hrtimer queues. These queues are evaluated
> only when the hardirq context detects that the first expiring timer in the
> softirq queues has expired. That makes the overhead in the hardirq context
> minimal.
>
> The series reworks the code to reuse as much as possible from the existing
> facilities for the new softirq hrtimers and integrates them with all
> flavours of hrtimers (HIGH_RES=y/n - NOHZ=y/n).
>
> To achieve this quite some of the conditionals in the existing code are
> removed for the price of adding some pointless data and state tracking to
> the HIGH_RES=n case. That's minimal, but well worth it as it increases the
> readability and maintainability of the code.
>
> The first part of the series implements the new functionality and the
> second part converts the hrtimer/tasklet users to make use of it and
> removes struct hrtimer_tasklet and the surrounding helper functions.
>
> This series is available from git as well:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/bigeasy/linux-hrtimer.git
> soft_hrtimer
> https://git.kernel.org/bigeasy/linux-hrtimer/h/soft_hrtimer
>
>
> Thanks,
>
> Anna-Maria
>
> ---
> drivers/net/usb/cdc_ncm.c | 37 +-
> drivers/net/wireless/mac80211_hwsim.c | 44 +-
> drivers/usb/gadget/function/f_ncm.c | 28 -
> include/linux/hrtimer.h | 76 ++---
> include/linux/interrupt.h | 25 -
> include/linux/usb/cdc_ncm.h | 2
> include/net/xfrm.h | 2
> kernel/softirq.c | 51 ---
> kernel/time/hrtimer.c | 513
> +++++++++++++++++++++-------------
> net/can/bcm.c | 150 +++------
> net/xfrm/xfrm_state.c | 29 +
> sound/drivers/dummy.c | 16 -
> 12 files changed, 484 insertions(+), 489 deletions(-)
>
>
