Allow a transition from the softirq stack to the hardirq stack when
handling a hardirq. Doing so means a hardirq received while deep in
softirq processing is less likely to cause a stack overflow of the
softirq stack.
Previously it wasn't safe to do so because irq_exit() (which initiates
softirq processing) was called on the hardirq stack.
That was changed in commit 1b1b6a6f4cc0 ("powerpc: handle irq_enter/
irq_exit in interrupt handler wrappers") and 1346d00e1bdf ("powerpc:
Don't select HAVE_IRQ_EXIT_ON_IRQ_STACK").
The allowed transitions are now:
- process stack -> hardirq stack
- process stack -> softirq stack
- process stack -> softirq stack -> hardirq stack
Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
---
arch/powerpc/kernel/irq.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 6f7d4edaa0bc..7504ceec5c58 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -284,15 +284,14 @@ static __always_inline void call_do_irq(struct pt_regs
*regs, void *sp)
void __do_IRQ(struct pt_regs *regs)
{
struct pt_regs *old_regs = set_irq_regs(regs);
- void *cursp, *irqsp, *sirqsp;
+ void *cursp, *irqsp;
/* Switch to the irq stack to handle this */
cursp = (void *)(current_stack_pointer & ~(THREAD_SIZE - 1));
irqsp = hardirq_ctx[raw_smp_processor_id()];
- sirqsp = softirq_ctx[raw_smp_processor_id()];
/* Already there ? If not switch stack and call */
- if (unlikely(cursp == irqsp || cursp == sirqsp))
+ if (unlikely(cursp == irqsp))
__do_irq(regs, current_stack_pointer);
else
call_do_irq(regs, irqsp);
--
2.41.0
