[PATCH] sparc64: Fix irqtrace warnings on Ultra-S

From: peterz
Date: Tue Sep 08 2020 - 15:43:26 EST

On Tue, Sep 08, 2020 at 07:40:23AM -0700, Guenter Roeck wrote:
> qemu-system-sparc64 -M sun4u -cpu "TI UltraSparc IIi" -m 512 \
> -initrd rootfs.cpio \
> -kernel arch/sparc/boot/image -no-reboot \
> -append "panic=-1 slub_debug=FZPUA rdinit=/sbin/init console=ttyS0" \
> -nographic -monitor none

Thanks I got it. Also enabling DEBUG_LOCKDEP helps (-:

Subject: sparc64: Fix irqtrace warnings on Ultra-S

Recent changes in Lockdep's IRQTRACE broke Ultra-S.

In order avoid redundant IRQ state changes, local_irq_restore() lost the
ability to trace a disable. Change the code to use local_irq_save() to
disable IRQs and then use arch_local_irq_restore() to further disable

This result in slightly suboptimal code, but given this code uses a
global spinlock, performance cannot be its primary purpose.

Fixes: 044d0d6de9f5 ("lockdep: Only trace IRQ edges")
Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
A possible alternative would be:

arch_local_irq_restore((unsigned long)PIL_NMI);

which generates optimal code, but is more verbose.

arch/sparc/prom/p1275.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/sparc/prom/p1275.c b/arch/sparc/prom/p1275.c
index 889aa602f8d8..e22233fcf741 100644
--- a/arch/sparc/prom/p1275.c
+++ b/arch/sparc/prom/p1275.c
@@ -37,16 +37,15 @@ void p1275_cmd_direct(unsigned long *args)
unsigned long flags;

- local_save_flags(flags);
- local_irq_restore((unsigned long)PIL_NMI);
+ local_irq_save(flags);
+ arch_local_irq_restore((unsigned long)PIL_NMI);


- raw_spin_unlock(&prom_entry_lock);
- local_irq_restore(flags);
+ raw_spin_unlock_irqrestore(&prom_entry_lock, flags);

void prom_cif_init(void *cif_handler, void *cif_stack)