On Fri, 26 Jan 2024 18:31:19 -0600 Samuel Holland <samuel.holland@xxxxxxxxxx> wrote: > On 2024-01-26 4:38 PM, Nam Cao wrote: > > RISC-V PLIC cannot EOI disabled interrupts, as explained in the > > description of Interrupt Completion in the PLIC spec: > > > > "The PLIC signals it has completed executing an interrupt handler by > > writing the interrupt ID it received from the claim to the claim/complete > > register. The PLIC does not check whether the completion ID is the same > > as the last claim ID for that target. If the completion ID does not match > > an interrupt source that *is currently enabled* for the target, the > > completion is silently ignored." > > > > Commit 69ea463021be ("irqchip/sifive-plic: Fixup EOI failed when masked") > > ensured that by enabling the interrupt if needed before EOI. > > > > Commit a1706a1c5062 ("irqchip/sifive-plic: Separate the enable and mask > > operations") removed the interrupt enabling code from the previous > > commit, because it assumes that interrupt should be enabled at the point > > of EOI. However, this is incorrect: there is a small window after a hart > > claiming an interrupt and before irq_desc->lock getting acquired, > > interrupt can be disabled during this window. Thus, EOI can be invoked > > while the interrupt is disabled, effectively nullify this EOI. > > > > Make sure that interrupt is really enabled before EOI. > > Could you please try the patch I previously sent for this issue[1]? Unfortunately my system still gets frozen with the patch applied :( I think because the patch doesn't prevent plic_irq_shutdown() from getting called after the hart claiming the interrupt and before irq_desc is locked up. > It should fix the bug without complicating the IRQ hot path. I can add an unlikely() to help that a bit, because from my experience, it is quite rare that EOI happens with interrupt disabled. Best regards, Nam