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

Nicholas Piggin
2020-09-14T04:52:45Z

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(-)

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2.23.0