Re: [PATCH 00/26] Convert locks that can't sleep in -rt to raw_spinlock

[Frederic Weisbecker <fweisbec@gmail.com>]

On Tue, Jan 12, 2010 at 04:24:29AM +0100, Frederic Weisbecker wrote:
> On Mon, Jan 11, 2010 at 10:26:30PM +0100, John Kacur wrote:
> > Thomas:
> > 
> > Now that your changes that free up the raw_spinlock name are upstream.
> > (described below for other readers)
> > 
> > http://lwn.net/Articles/365863/
> > http://lwn.net/Articles/366608/
> > 
> > I wanted to forward port the preempt-rt patches that convert locks to
> > atomic_spinlocks (rt tree only) to the new scheme.
> > 
> > The patches below are a result of that effort.
> > Please queue these up for 2.6.34 upstream, and please pull for preempt-rt
> > 
> > You can pull them from
> > git://git.kernel.org/pub/scm/linux/kernel/git/jkacur/jk-2.6.git
> > jk/v2.6.33-rc3-raw-spinlocks
> > 
> > Thanks
> > 
> > John Kacur (25):
> >   xtime_lock: Convert atomic_seqlock to raw_seqlock, fix up all users
> >   x86: Convert tlbstate_lock to raw_spinlock
> >   sched: Convert thread_group_cputimer lock to raw_spinlock
> >   x86: Convert ioapic_lock and vector_lock to raw_spinlocks
> >   x86: Convert i8259A_lock to raw_spinlock
> >   x86: Convert pci_config_lock to raw_spinlock
> >   i8253: Convert i8253_lock to raw_spinlock
> >   x86: Convert set_atomicity_lock to raw_spinlock
> >   ACPI: Convert c3_lock to raw_spinlock
> >   rtmutex: Convert wait_lock and pi_lock to raw_spinlock
> >   printk: Convert lock to raw_spinlock
> >   genirq: Convert locks to raw_spinlocks
> >   trace: Convert various locks to raw_spinlock
> >   clocksource: Convert watchdog_lock to raw_spinlock
> >   timer_stats: Convert to raw_spinlocks
> >   x86: kvm: Convert i8254/i8259 locks to raw_spinlock
> >   x86 - nmi: Convert nmi_lock to raw_spinlock
> >   cgroups: Convert cgroups release_list_lock to raw_spinlock
> >   proportions: Convert spinlocks to raw_spinlocks.
> >   percpu_counter: Convert to raw_spinlock
> >   oprofile: Convert to raw_spinlock
> >   vgacon: Convert vga console lock to raw_spinlock
> >   pci-access: Convert pci_lock to raw_spinlock
> >   kprobes: Convert to raw_spinlocks
> >   softlockup: Convert to raw_spinlocks
> > 
> > Thomas Gleixner (1):
> >   seqlock: Create raw_seqlock
> > 
> >  arch/alpha/kernel/time.c            |    4 +-
> >  arch/arm/kernel/time.c              |   12 ++--
> >  arch/arm/oprofile/common.c          |    4 +-
> >  arch/arm/oprofile/op_model_mpcore.c |    4 +-
> >  arch/blackfin/kernel/time.c         |    4 +-
> >  arch/cris/kernel/time.c             |    4 +-
> >  arch/frv/kernel/time.c              |    4 +-
> >  arch/h8300/kernel/time.c            |    4 +-
> >  arch/ia64/kernel/time.c             |    4 +-
> >  arch/ia64/xen/time.c                |    4 +-
> >  arch/m32r/kernel/time.c             |    4 +-
> >  arch/m68knommu/kernel/time.c        |    4 +-
> >  arch/mips/include/asm/i8253.h       |    2 +-
> >  arch/mips/kernel/i8253.c            |   14 ++--
> >  arch/mn10300/kernel/time.c          |    4 +-
> >  arch/parisc/kernel/time.c           |    8 +-
> >  arch/powerpc/kernel/time.c          |    4 +-
> >  arch/sparc/kernel/pcic.c            |    8 +-
> >  arch/sparc/kernel/time_32.c         |   12 ++--
> >  arch/x86/include/asm/i8253.h        |    2 +-
> >  arch/x86/include/asm/i8259.h        |    2 +-
> >  arch/x86/include/asm/pci_x86.h      |    2 +-
> >  arch/x86/kernel/apic/io_apic.c      |  106 +++++++++++++++++-----------------
> >  arch/x86/kernel/apic/nmi.c          |    6 +-
> >  arch/x86/kernel/apm_32.c            |    4 +-
> >  arch/x86/kernel/cpu/mtrr/generic.c  |    6 +-
> >  arch/x86/kernel/i8253.c             |   14 ++--
> >  arch/x86/kernel/i8259.c             |   30 +++++-----
> >  arch/x86/kernel/time.c              |    4 +-
> >  arch/x86/kernel/visws_quirks.c      |    6 +-
> >  arch/x86/kvm/i8254.c                |   10 ++--
> >  arch/x86/kvm/i8254.h                |    2 +-
> >  arch/x86/kvm/i8259.c                |   30 +++++-----
> >  arch/x86/kvm/irq.h                  |    2 +-
> >  arch/x86/kvm/x86.c                  |    8 +-
> >  arch/x86/mm/tlb.c                   |    8 +-
> >  arch/x86/oprofile/nmi_int.c         |    4 +-
> >  arch/x86/pci/common.c               |    2 +-
> >  arch/x86/pci/direct.c               |   16 +++---
> >  arch/x86/pci/mmconfig_32.c          |    8 +-
> >  arch/x86/pci/numaq_32.c             |    8 +-
> >  arch/x86/pci/pcbios.c               |    8 +-
> >  arch/xtensa/kernel/time.c           |    4 +-
> >  drivers/acpi/processor_idle.c       |   10 ++--
> >  drivers/block/hd.c                  |    4 +-
> >  drivers/input/gameport/gameport.c   |    4 +-
> >  drivers/input/joystick/analog.c     |    4 +-
> >  drivers/input/misc/pcspkr.c         |    6 +-
> >  drivers/oprofile/event_buffer.c     |    4 +-
> >  drivers/oprofile/oprofilefs.c       |    6 +-
> >  drivers/pci/access.c                |   34 ++++++------
> >  drivers/video/console/vgacon.c      |   42 +++++++-------
> >  include/linux/init_task.h           |    2 +-
> >  include/linux/kprobes.h             |    2 +-
> >  include/linux/oprofile.h            |    2 +-
> >  include/linux/percpu_counter.h      |    2 +-
> >  include/linux/proportions.h         |    6 +-
> >  include/linux/ratelimit.h           |    4 +-
> >  include/linux/rtmutex.h             |    2 +-
> >  include/linux/sched.h               |    4 +-
> >  include/linux/seqlock.h             |   86 +++++++++++++++++++++++++++-
> >  include/linux/time.h                |    2 +-
> >  kernel/cgroup.c                     |   18 +++---
> >  kernel/hrtimer.c                    |    8 +-
> >  kernel/kprobes.c                    |   34 ++++++------
> >  kernel/posix-cpu-timers.c           |    8 +-
> >  kernel/printk.c                     |   42 +++++++-------
> >  kernel/sched_stats.h                |   12 ++--
> >  kernel/softlockup.c                 |    6 +-
> >  kernel/time.c                       |    8 +-
> >  kernel/time/clocksource.c           |   26 ++++----
> >  kernel/time/ntp.c                   |    8 +-
> >  kernel/time/tick-common.c           |    8 +-
> >  kernel/time/tick-sched.c            |   12 ++--
> >  kernel/time/timekeeping.c           |   50 ++++++++--------
> >  kernel/time/timer_stats.c           |    6 +-
> >  kernel/trace/ring_buffer.c          |   52 +++++++++---------
> >  kernel/trace/trace.c                |   10 ++--
> >  kernel/trace/trace_irqsoff.c        |    6 +-
> >  lib/percpu_counter.c                |   18 +++---
> >  lib/proportions.c                   |   12 ++--
> >  lib/ratelimit.c                     |    4 +-
> >  sound/drivers/pcsp/pcsp.h           |    2 +-
> >  sound/drivers/pcsp/pcsp_input.c     |    4 +-
> >  sound/drivers/pcsp/pcsp_lib.c       |   12 ++--
> >  85 files changed, 535 insertions(+), 457 deletions(-)
> 
> 
> 
> Looking at this whole patchset. I have the feeling the
> changelogs don't tell us much about why we do that.
> 
> I mean, I understand the general purpose of this patchset,
> but taken invidually, some of them make me stuck into
> existential questions.
> 
> Could you just at least put a one liner detailed and
> individual clue in the changelogs that tells us why a
> pointed spinlock can not sleep in preempt_rt? And may
> be a comment in the code? There are places where it
> is pretty obvious, such as the rq lock. But some
> others...
> 
> Or may be I'm just too ignorant and these sleeping
> in rt places are just simply damn too obvious to deserve
> any individual words... :-)
> 
> Thanks.
> 


And please add people working on these files in Cc.