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  1. 09 Feb, 2018 16 commits
  3. 28 Jan, 2018 8 commits
  5. 27 Jan, 2018 2 commits
    • Thomas Gleixner's avatar
      hrtimer: Reset hrtimer cpu base proper on CPU hotplug · d5421ea4
      Thomas Gleixner authored 
      The hrtimer interrupt code contains a hang detection and mitigation
mechanism, which prevents that a long delayed hrtimer interrupt causes a
continous retriggering of interrupts which prevent the system from making
progress. If a hang is detected then the timer hardware is programmed with
a certain delay into the future and a flag is set in the hrtimer cpu base
which prevents newly enqueued timers from reprogramming the timer hardware
prior to the chosen delay. The subsequent hrtimer interrupt after the delay
clears the flag and resumes normal operation.

If such a hang happens in the last hrtimer interrupt before a CPU is
unplugged then the hang_detected flag is set and stays that way when the
CPU is plugged in again. At that point the timer hardware is not armed and
it cannot be armed because the hang_detected flag is still active, so
nothing clears that flag. As a consequence the CPU does not receive hrtimer
interrupts and no timers expire on that CPU which results in RCU stalls and
other malfunctions.

Clear the flag along with some other less critical members of the hrtimer
cpu base to ensure starting from a clean state when a CPU is plugged in.

Thanks to Paul, Sebastian and Anna-Maria for their help to get down to the
root cause of that hard to reproduce heisenbug. Once understood it's
trivial and certainly justifies a brown paperbag.

Fixes: 41d2e494 ("hrtimer: Tune hrtimer_interrupt hang logic")
Reported-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Sewior <bigeasy@linutronix.de>
Cc: Anna-Maria Gleixner <anna-maria@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1801261447590.2067@nanos
      d5421ea4
    • H. Peter Anvin's avatar
      x86: Mark hpa as a "Designated Reviewer" for the time being · 8a95b74d
      H. Peter Anvin authored 
      Due to some unfortunate events, I have not been directly involved in
the x86 kernel patch flow for a while now.  I have also not been able
to ramp back up by now like I had hoped to, and after reviewing what I
will need to work on both internally at Intel and elsewhere in the near
term, it is clear that I am not going to be able to ramp back up until
late 2018 at the very earliest.

It is not acceptable to not recognize that this load is currently
taken by Ingo and Thomas without my direct participation, so I mark
myself as R: (designated reviewer) rather than M: (maintainer) until
further notice.  This is in fact recognizing the de facto situation
for the past few years.

I have obviously no intention of going away, and I will do everything
within my power to improve Linux on x86 and x86 for Linux.  This,
however, puts credit where it is due and reflects a change of focus.

This patch also removes stale entries for portions of the x86
architecture which have not been maintained separately from arch/x86
for a long time.  If there is a reason to re-introduce them then that
can happen later.
Signed-off-by: default avatarH. Peter Anvin <h.peter.anvin@intel.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Bruce Schlobohm <bruce.schlobohm@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180125195934.5253-1-hpa@zytor.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
      8a95b74d
  7. 26 Jan, 2018 13 commits
  9. 25 Jan, 2018 1 commit
    • Lyude Paul's avatar
      drm/nouveau: Move irq setup/teardown to pci ctor/dtor · 0fd189a9
      Lyude Paul authored 
      For a while we've been having issues with seemingly random interrupts
coming from nvidia cards when resuming them. Originally the fix for this
was thought to be just re-arming the MSI interrupt registers right after
re-allocating our IRQs, however it seems a lot of what we do is both
wrong and not even nessecary.

This was made apparent by what appeared to be a regression in the
mainline kernel that started introducing suspend/resume issues for
nouveau:

        a0c9259d (irq/matrix: Spread interrupts on allocation)

After this commit was introduced, we started getting interrupts from the
GPU before we actually re-allocated our own IRQ (see references below)
and assigned the IRQ handler. Investigating this turned out that the
problem was not with the commit, but the fact that nouveau even
free/allocates it's irqs before and after suspend/resume.

For starters: drivers in the linux kernel haven't had to handle
freeing/re-allocating their IRQs during suspend/resume cycles for quite
a while now. Nouveau seems to be one of the few drivers left that still
does this, despite the fact there's no reason we actually need to since
disabling interrupts from the device side should be enough, as the
kernel is already smart enough to know to disable host-side interrupts
for us before going into suspend. Since we were tearing down our IRQs by
hand however, that means there was a short period during resume where
interrupts could be received before we re-allocated our IRQ which would
lead to us getting an unhandled IRQ. Since we never handle said IRQ and
re-arm the interrupt registers, this would cause us to miss all of the
interrupts from the GPU and cause our init process to start timing out
on anything requiring interrupts.

So, since this whole setup/teardown every suspend/resume cycle is
useless anyway, move irq setup/teardown into the pci subdev's ctor/dtor
functions instead so they're only called at driver load and driver
unload. This should fix most of the issues with pending interrupts on
resume, along with getting suspend/resume for nouveau to work again.

As well, this probably means we can also just remove the msi rearm call
inside nvkm_pci_init(). But since our main focus here is to fix
suspend/resume before 4.15, we'll save that for a later patch.
Signed-off-by: default avatarLyude Paul <lyude@redhat.com>
Cc: Karol Herbst <kherbst@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mike Galbraith <efault@gmx.de>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarBen Skeggs <bskeggs@redhat.com>
      0fd189a9
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