Re: [PATCH 0/3] Modernize tasklet callback API

Dmitry Torokhov
2020-07-16T20:51:56Z

On Thu, Jul 16, 2020 at 12:14 PM Kees Cook <keescook@chromium.org> wrote:
>
> On Thu, Jul 16, 2020 at 09:57:18AM +0200, Peter Zijlstra wrote:
> > On Wed, Jul 15, 2020 at 08:08:44PM -0700, Kees Cook wrote:
> > > Hi,
> > >
> > > This is the infrastructure changes to prepare the tasklet API for
> > > conversion to passing the tasklet struct as the callback argument instead
> > > of an arbitrary unsigned long. The first patch details why this is useful
> > > (it's the same rationale as the timer_struct changes from a bit ago:
> > > less abuse during memory corruption attacks, more in line with existing
> > > ways of doing things in the kernel, save a little space in struct,
> > > etc). Notably, the existing tasklet API use is much less messy, so there
> > > is less to clean up.
> >
> > I would _MUCH_ rather see tasklets go the way of the dodo, esp. given
> > that:
> >
> > > drivers/input/keyboard/omap-keypad.c | 2 +-
> > > drivers/input/serio/hil_mlc.c | 2 +-
> > > drivers/net/wan/farsync.c | 4 +--
> > > drivers/s390/crypto/ap_bus.c | 2 +-
> > > drivers/staging/most/dim2/dim2.c | 2 +-
> > > drivers/staging/octeon/ethernet-tx.c | 2 +-
> > > drivers/tty/vt/keyboard.c | 2 +-
> > > drivers/usb/gadget/udc/snps_udc_core.c | 6 ++---
> > > drivers/usb/host/fhci-sched.c | 2 +-
> > > include/linux/interrupt.h | 37 ++++++++++++++++++++++----
> > > kernel/backtracetest.c | 2 +-
> > > kernel/debug/debug_core.c | 2 +-
> > > kernel/irq/resend.c | 2 +-
> > > kernel/softirq.c | 18 ++++++++++++-
> > > net/atm/pppoatm.c | 2 +-
> > > net/iucv/iucv.c | 2 +-
> > > sound/drivers/pcsp/pcsp_lib.c | 2 +-
> > > 17 files changed, 66 insertions(+), 25 deletions(-)
> >
> > there appear to be hardly any users left.. Can't we stage an extinction
> > event here instead?
>
> Oh, I wish, but no. That's just the ones using DECLARE_TASKLET. There
> are hundred(s?) more (see the referenced tree).

Still, do we really need tasklets? Can we substitute timers executing
immediately in their place?

Thanks.

--
Dmitry