From c6baa077b784c3b37391a8c11f433e3f881a80df Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Fri, 29 Sep 2017 13:58:02 +1000 Subject: powerpc/powernv: Make opal_event_shutdown() callable from IRQ context In opal_event_shutdown() we free all the IRQs hanging off the opal_event_irqchip. However it's not safe to do so if we're called from IRQ context, because free_irq() wants to synchronise versus IRQ context. This can lead to warnings and a stuck system. For example from sysrq-b: Trying to free IRQ 17 from IRQ context! ------------[ cut here ]------------ WARNING: CPU: 0 PID: 0 at kernel/irq/manage.c:1461 __free_irq+0x398/0x8d0 ... NIP __free_irq+0x398/0x8d0 LR __free_irq+0x394/0x8d0 Call Trace: __free_irq+0x394/0x8d0 (unreliable) free_irq+0xa4/0x140 opal_event_shutdown+0x128/0x180 opal_shutdown+0x1c/0xb0 pnv_shutdown+0x20/0x40 machine_restart+0x38/0x90 emergency_restart+0x28/0x40 sysrq_handle_reboot+0x24/0x40 __handle_sysrq+0x198/0x590 hvc_poll+0x48c/0x8c0 hvc_handle_interrupt+0x1c/0x50 __handle_irq_event_percpu+0xe8/0x6e0 handle_irq_event_percpu+0x34/0xe0 handle_irq_event+0xc4/0x210 handle_level_irq+0x250/0x770 generic_handle_irq+0x5c/0xa0 opal_handle_events+0x11c/0x240 opal_interrupt+0x38/0x50 __handle_irq_event_percpu+0xe8/0x6e0 handle_irq_event_percpu+0x34/0xe0 handle_irq_event+0xc4/0x210 handle_fasteoi_irq+0x174/0xa10 generic_handle_irq+0x5c/0xa0 __do_irq+0xbc/0x4e0 call_do_irq+0x14/0x24 do_IRQ+0x18c/0x540 hardware_interrupt_common+0x158/0x180 We can avoid that by using disable_irq_nosync() rather than free_irq(). Although it doesn't fully free the IRQ, it should be sufficient when we're shutting down, particularly in an emergency. Add an in_interrupt() check and use free_irq() when we're shutting down normally. It's probably OK to use disable_irq_nosync() in that case too, but for now it's safer to leave that behaviour as-is. Fixes: 9f0fd0499d30 ("powerpc/powernv: Add a virtual irqchip for opal events") Reported-by: Anton Blanchard Signed-off-by: Michael Ellerman --- arch/powerpc/platforms/powernv/opal-irqchip.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/platforms/powernv/opal-irqchip.c b/arch/powerpc/platforms/powernv/opal-irqchip.c index ecdcba9d1220..9d1b8c0aaf93 100644 --- a/arch/powerpc/platforms/powernv/opal-irqchip.c +++ b/arch/powerpc/platforms/powernv/opal-irqchip.c @@ -174,8 +174,14 @@ void opal_event_shutdown(void) /* First free interrupts, which will also mask them */ for (i = 0; i < opal_irq_count; i++) { - if (opal_irqs[i]) + if (!opal_irqs[i]) + continue; + + if (in_interrupt()) + disable_irq_nosync(opal_irqs[i]); + else free_irq(opal_irqs[i], NULL); + opal_irqs[i] = 0; } } -- cgit v1.2.3-59-g8ed1b