Re: [PATCH] powerpc/entry: Use hard_irq_disable() in arch_interrupt_exit_prepare()

Le 13/08/2026 à 08:36, Venkat Rao Bagalkote a écrit :

On 12/08/26 8:50 pm, Mukesh Kumar Chaurasiya (IBM) wrote:

quoted

commit 334f3f6d7a16 ("powerpc/entry: Disable interrupts before 
irqentry_exit")
fixed a BUG in preempt_schedule_irq() by calling local_irq_disable()
unconditionally in arch_interrupt_exit_prepare() before irqentry_exit().
The fix is correct in intent but uses the wrong primitive for PPC64.

On PPC64, local_irq_disable() only sets the soft-mask
(irq_soft_mask = IRQS_DISABLED). It does not set PACA_IRQ_HARD_DIS in
irq_happened and does not clear MSR[EE].

This causes a continuous WARN_ON boot hang on Power11 pSeries LPARs
using the dedicated-cede cpuidle path. When the CPU wakes from H_CEDE,
interrupt_exit_kernel_prepare() calls replay_soft_interrupts(), which
dispatches pending async handlers (timer_interrupt, do_IRQ) using the
DEFINE_INTERRUPT_HANDLER_ASYNC macro. That macro calls
arch_interrupt_async_exit_prepare() -> arch_interrupt_exit_prepare()
before irqentry_exit(). With local_irq_disable(), PACA_IRQ_HARD_DIS
is not set, but next_interrupt() unconditionally asserts it:

   WARN_ON(!(local_paca->irq_happened & PACA_IRQ_HARD_DIS));

This fires on every replayed interrupt, looping indefinitely and
preventing boot completion.

Fix this by replacing local_irq_disable() with hard_irq_disable().
On PPC64, hard_irq_disable() sets irq_soft_mask to IRQS_ALL_DISABLED,
sets PACA_IRQ_HARD_DIS in irq_happened, and clears MSR[EE] — satisfying
all of:

   - lockdep_assert_irqs_disabled() in irqentry_exit_to_kernel_mode()
   - next_interrupt()'s WARN_ON(!(irq_happened & PACA_IRQ_HARD_DIS))
   - preempt_schedule_irq()'s BUG_ON(!irqs_disabled())

On PPC32/non-64, hard_irq_disable() is equivalent to local_irq_disable(),
so there is no regression on those platforms.

Fixes: 334f3f6d7a16 ("powerpc/entry: Disable interrupts before 
irqentry_exit")
Reported-by: Venkat Rao Bagalkote <redacted>
Closes: https://eur01.safelinks.protection.outlook.com/? 
url=https%3A%2F%2Flore.kernel.org%2Fall%2F6f9bfb0f-b14c-468e-bb9f- 
c157d120d0dc%40linux.ibm.com%2F&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7Cf780f6a2abcf425c875808def90533e4%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639221997929524168%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=kOer%2B610LkQs0ZKBn%2FutIB6j1bMoFasK4DmX4AEWOXA%3D&reserved=0
Signed-off-by: Mukesh Kumar Chaurasiya (IBM) <redacted>
---

Tested this, and it fixes the reported issue.

Tested-by: Venkat Rao Bagalkote <redacted>

Didn't you say yesterday [1] that the change doesn't fix the issue ? Did 
I miss something ?

[1] 
https://lore.kernel.org/all/2f7e6c34-7258-4b20-a38e-cedebccb835f@linux.ibm.com/ (local)

Regards,

Venkat.

quoted

  arch/powerpc/include/asm/entry-common.h | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/entry-common.h b/arch/powerpc/ 

include/asm/entry-common.h
index c5adb5006361..de64389b0815 100644

--- a/arch/powerpc/include/asm/entry-common.h
+++ b/arch/powerpc/include/asm/entry-common.h

@@ -270,7 +270,7 @@ static inline void 

arch_interrupt_exit_prepare(struct pt_regs *regs)
      }
      /* irqentry_exit expects to be called with interrupts disabled */
-    local_irq_disable();
+    hard_irq_disable();
  }
  static inline void arch_interrupt_async_enter_prepare(struct pt_regs 
*regs)