Re: [PATCH] risc-v: Fix order of IPI enablement vs RCU startup

Marc Zyngier
2023-07-03T18:58:10Z

On Mon, 03 Jul 2023 19:45:43 +0100,
Palmer Dabbelt <palmer@rivosinc.com> wrote:
>
> On Mon, 03 Jul 2023 11:31:26 PDT (-0700), Marc Zyngier wrote:
> > Conor reports that risc-v tries to enable IPIs before telling the
> > core code to enable RCU. With the introduction of the mapple tree
> > as a backing store for the irq descriptors, this results in
> > a very shouty boot sequence, as RCU is legitimately upset.
> >
> > Restore some sanity by moving the risc_ipi_enable() call after
> > notify_cpu_starting(), which explicitly enables RCU on the calling
> > CPU.
> >
> > Fixes: 832f15f42646 ("RISC-V: Treat IPIs as normal Linux IRQs")
> > Reported-by: Conor Dooley <conor@kernel.org>
> > Signed-off-by: Marc Zyngier <maz@kernel.org>
> > Link: https://lore.kernel.org/r/20230703-dupe-frying-79ae2ccf94eb@spud
> > Cc: Anup Patel <apatel@ventanamicro.com>
> > Cc: Palmer Dabbelt <palmer@rivosinc.com>
> > Cc: Linus Torvalds <torvalds@linux-foundation.org>
> > ---
> > arch/riscv/kernel/smpboot.c | 5 +++--
> > 1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
> > index bb0b76e1a6d4..f4d6acb38dd0 100644
> > --- a/arch/riscv/kernel/smpboot.c
> > +++ b/arch/riscv/kernel/smpboot.c
> > @@ -238,10 +238,11 @@ asmlinkage __visible void smp_callin(void)
> > mmgrab(mm);
> > current->active_mm = mm;
> >
> > - riscv_ipi_enable();
> > -
> > store_cpu_topology(curr_cpuid);
> > notify_cpu_starting(curr_cpuid);
> > +
> > + riscv_ipi_enable();
> > +
> > numa_add_cpu(curr_cpuid);
> > set_cpu_online(curr_cpuid, 1);
> > probe_vendor_features(curr_cpuid);
>
> Thanks. I was going to send another PR this week anyway, I can just
> pick this up if you want?

Yes please!

M.

--
Without deviation from the norm, progress is not possible.