Re: [PATCH] powerpc/irq: Allow softirq to hardirq stack transition
From: Christophe Leroy <hidden>
Date: 2023-11-30 15:17:23
Le 30/11/2023 à 13:50, Michael Ellerman a écrit :
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 stackIt means you don't like my patch https://patchwork.ozlabs.org/project/linuxppc-dev/patch/6cd9d8bb2258d8b51999c2584eac74423d2b5e29.1657203774.git.christophe.leroy@csgroup.eu/ ? I never got any feedback.
quoted hunk ↗ jump to hunk
Signed-off-by: Michael Ellerman <mpe@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);