From 4eb20bf34ea296f648971a8528e32cd80efcbe89 Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Thu, 30 Nov 2023 23:50:45 +1100 Subject: powerpc/irq: Allow softirq to hardirq stack transition 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 Reviewed-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://msgid.link/20231130125045.3080961-1-mpe@ellerman.id.au --- arch/powerpc/kernel/irq.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) (limited to 'arch/powerpc') 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); -- cgit v1.2.3