There is a vector setup race, which overwrites the interrupt descriptor in the per CPU vector array resulting in a disfunctional device.
CPU0 CPU1 interrupt is raised in APIC IRR but not handled free_irq() per_cpu(vector_irq, CPU1)[vector] = VECTOR_SHUTDOWN;
request_irq() common_interrupt() d = this_cpu_read(vector_irq[vector]);
per_cpu(vector_irq, CPU1)[vector] = desc;
if (d == VECTOR_SHUTDOWN) this_cpu_write(vector_irq[vector], VECTOR_UNUSED);
free_irq() cannot observe the pending vector in the CPU1 APIC as there is no way to query the remote CPUs APIC IRR.
This requires that request_irq() uses the same vector/CPU as the one which was freed, but this also can be triggered by a spurious interrupt.
Interestingly enough this problem managed to be hidden for more than a decade.
Prevent this by reevaluating vector_irq under the vector lock, which is held by the interrupt activation code when vector_irq is updated.
The first patch provides context for subsequent real bugfix patch.
Fixes: 9345005f4eed ("x86/irq: Fix do_IRQ() interrupt warning for cpu hotplug retriggered irqs") Cc: stable@vger.kernel.org#5.10.x Cc: gregkh@linuxfoundation.org
v1 -> RESEND - Add upstream commit ID.
Jacob Pan (1): x86/irq: Factor out handler invocation from common_interrupt()
Thomas Gleixner (1): x86/irq: Plug vector setup race
arch/x86/kernel/irq.c | 70 ++++++++++++++++++++++++++++++++++--------- 1 file changed, 56 insertions(+), 14 deletions(-)