membarrier: riscv: Add full memory barrier in switch_mm()

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The membarrier system call requires a full memory barrier after storing
to rq->curr, before going back to user-space.  The barrier is only
needed when switching between processes: the barrier is implied by
mmdrop() when switching from kernel to userspace, and it's not needed
when switching from userspace to kernel.

Rely on the feature/mechanism ARCH_HAS_MEMBARRIER_CALLBACKS and on the
primitive membarrier_arch_switch_mm(), already adopted by the PowerPC
architecture, to insert the required barrier.

Fixes: fab957c11e ("RISC-V: Atomic and Locking Code")
Signed-off-by: Andrea Parri <parri.andrea@gmail.com>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/r/20240131144936.29190-2-parri.andrea@gmail.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

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Andrea Parri 2024-01-31 15:49:33 +01:00 • committed by Palmer Dabbelt

parent 6613476e22

commit d6cfd1770f

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5 changed files with 38 additions and 3 deletions

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2

MAINTAINERS

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arch/riscv/Kconfig

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31

arch/riscv/include/asm/membarrier.h

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arch/riscv/mm/context.c

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kernel/sched/core.c

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