[v2,0/4] more mm switching vs TLB shootdown and lazy tlb fixes

Message

Nicholas Piggin Sept. 14, 2020, 4:52 a.m. UTC

This is an attempt to fix a few different related issues around
switching mm, TLB flushing, and lazy tlb mm handling.

This will require all architectures to eventually move to disabling
irqs over activate_mm, but it's possible we could add another arch
call after irqs are re-enabled for those few which can't do their
entire activation with irqs disabled.

Testing so far indicates this has fixed a mm refcounting bug that
powerpc was running into (via distro report and backport). I haven't
had any real feedback on this series outside powerpc (and it doesn't
really affect other archs), so I propose patches 1,2,4 go via the
powerpc tree.

There is no dependency between them and patch 3, I put it there only
because it follows the history of the code (powerpc code was written
using the sparc64 logic), but I guess they have to go via different arch
trees. Dave, I'll leave patch 3 with you.

Thanks,
Nick

Since v1:
- Updates from Michael Ellerman's review comments.

Nicholas Piggin (4):
  mm: fix exec activate_mm vs TLB shootdown and lazy tlb switching race
  powerpc: select ARCH_WANT_IRQS_OFF_ACTIVATE_MM
  sparc64: remove mm_cpumask clearing to fix kthread_use_mm race
  powerpc/64s/radix: Fix mm_cpumask trimming race vs kthread_use_mm

 arch/Kconfig                           |  7 +++
 arch/powerpc/Kconfig                   |  1 +
 arch/powerpc/include/asm/mmu_context.h |  2 +-
 arch/powerpc/include/asm/tlb.h         | 13 ------
 arch/powerpc/mm/book3s64/radix_tlb.c   | 23 ++++++---
 arch/sparc/kernel/smp_64.c             | 65 ++++++--------------------
 fs/exec.c                              | 17 ++++++-
 7 files changed, 54 insertions(+), 74 deletions(-)

Comments

Michael Ellerman Sept. 24, 2020, 12:28 p.m. UTC | #1

On Mon, 14 Sep 2020 14:52:15 +1000, Nicholas Piggin wrote:
> This is an attempt to fix a few different related issues around
> switching mm, TLB flushing, and lazy tlb mm handling.
> 
> This will require all architectures to eventually move to disabling
> irqs over activate_mm, but it's possible we could add another arch
> call after irqs are re-enabled for those few which can't do their
> entire activation with irqs disabled.
> 
> [...]

Applied to powerpc/next.

[1/4] mm: fix exec activate_mm vs TLB shootdown and lazy tlb switching race
      https://git.kernel.org/powerpc/c/d53c3dfb23c45f7d4f910c3a3ca84bf0a99c6143
[2/4] powerpc: select ARCH_WANT_IRQS_OFF_ACTIVATE_MM
      https://git.kernel.org/powerpc/c/66acd46080bd9e5ad2be4b0eb1d498d5145d058e
[3/4] sparc64: remove mm_cpumask clearing to fix kthread_use_mm race
      https://git.kernel.org/powerpc/c/bafb056ce27940c9994ea905336aa8f27b4f7275
[4/4] powerpc/64s/radix: Fix mm_cpumask trimming race vs kthread_use_mm
      https://git.kernel.org/powerpc/c/a665eec0a22e11cdde708c1c256a465ebe768047

cheers