Hi Nick,

Le 19/07/2017 à 08:59, Nicholas Piggin a écrit :
Use nmi_enter similarly to system reset interrupts. This uses NMI
printk NMI buffers and turns off various debugging facilities that
helps avoid tripping on ourselves or other CPUs.

Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
  arch/powerpc/kernel/traps.c | 9 ++++++---
  1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 2849c4f50324..6d31f9d7c333 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -789,8 +789,10 @@ int machine_check_generic(struct pt_regs *regs)
void machine_check_exception(struct pt_regs *regs)
  {
-       enum ctx_state prev_state = exception_enter();
        int recover = 0;
+       bool nested = in_nmi();
+       if (!nested)
+               nmi_enter();

This alters preempt_count, then when die() is called
in_interrupt() returns true allthough the trap didn't happen in interrupt, so oops_end() panics for "fatal exception in interrupt" instead of gently sending SIGBUS the faulting app.

Any idea on how to fix this ?

Christophe

__this_cpu_inc(irq_stat.mce_exceptions); @@ -820,10 +822,11 @@ void machine_check_exception(struct pt_regs *regs) /* Must die if the interrupt is not recoverable */
        if (!(regs->msr & MSR_RI))
-               panic("Unrecoverable Machine check");
+               nmi_panic(regs, "Unrecoverable Machine check");
bail:
-       exception_exit(prev_state);
+       if (!nested)
+               nmi_exit();
  }
void SMIException(struct pt_regs *regs)

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