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* [PATCH] powerpc/powernv: Make opal_event_shutdown() callable from IRQ context
@ 2017-09-29  3:58 Michael Ellerman
  2017-09-29  5:24 ` Balbir Singh
  2017-10-08  8:43 ` Michael Ellerman
  0 siblings, 2 replies; 3+ messages in thread
From: Michael Ellerman @ 2017-09-29  3:58 UTC (permalink / raw)
  To: linuxppc-dev; +Cc: anton, rlippert

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")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---
 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;
 	}
 }
-- 
2.7.4

^ permalink raw reply related	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2017-10-08  8:43 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
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2017-09-29  3:58 [PATCH] powerpc/powernv: Make opal_event_shutdown() callable from IRQ context Michael Ellerman
2017-09-29  5:24 ` Balbir Singh
2017-10-08  8:43 ` Michael Ellerman

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