Venkat reported a panic on powerpc-next tree where GENERIC_ENTRY has
been enabled.
kernel BUG at kernel/sched/core.c:7512!
NIP preempt_schedule_irq+0x44/0x118
LR dynamic_irqentry_exit_cond_resched+0x40/0x1a4
Call Trace:
dynamic_irqentry_exit_cond_resched+0x40/0x1a4
do_page_fault+0xc0/0x104
data_access_common_virt+0x210/0x220
This happens since __do_page_fault ends up enabling the interrupts and
it could take significant time such that need_resched could be set. This
leads to schedule call in irqentry_exit leading to the bug.
There are many such irq handlers which enables the interrupts.
Fix it by disabling the irq before calling irqentry_exit. The same
pattern exists today in interrupt_exit_kernel_prepare.
While there, make those BUG_ON into WARN_ON. Interrupt is disabled right
after so it is not that severe. This will still help to catch the
offending callsites.
Fixes: bee25f97ad24 ("powerpc: Enable GENERIC_ENTRY feature")
Reported-by: Venkat Rao Bagalkote <[email protected]>
Closes:
https://lore.kernel.org/all/[email protected]/
Signed-off-by: Shrikanth Hegde <[email protected]>
---
This applies on top on powerpc/next tree.
base: 6ed60999d33d '("powerpc: Remove unused functions")'
arch/powerpc/include/asm/entry-common.h | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/include/asm/entry-common.h
b/arch/powerpc/include/asm/entry-common.h
index de5601282755..7da373a56813 100644
--- a/arch/powerpc/include/asm/entry-common.h
+++ b/arch/powerpc/include/asm/entry-common.h
@@ -253,16 +253,17 @@ static inline void arch_interrupt_enter_prepare(struct
pt_regs *regs)
static inline void arch_interrupt_exit_prepare(struct pt_regs *regs)
{
if (user_mode(regs)) {
- BUG_ON(regs_is_unrecoverable(regs));
- BUG_ON(regs_irqs_disabled(regs));
+ WARN_ON(regs_is_unrecoverable(regs));
+ WARN_ON(regs_irqs_disabled(regs));
/*
* We don't need to restore AMR on the way back to userspace
for KUAP.
* AMR can only have been unlocked if we interrupted the kernel.
*/
kuap_assert_locked();
-
- local_irq_disable();
}
+
+ /* irqentry_exit expects to be called with interrupts disabled */
+ local_irq_disable();
}
static inline void arch_interrupt_async_enter_prepare(struct pt_regs *regs)
--
2.47.3
