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authorAlistair Popple <alistair@popple.id.au>2015-12-18 17:16:17 +1100
committerMichael Ellerman <mpe@ellerman.id.au>2015-12-18 22:24:15 +1100
commit036592fbbe753d236402a0ae68148e7c143a0f0e (patch)
treed2f05d8738a0e78ed8227f10c0b55eff3b23cfaf /arch
parent98da62b716a3b24ab8e77453c9a8a954124c18cd (diff)
downloadlinux-stericsson-036592fbbe753d236402a0ae68148e7c143a0f0e.tar.gz
powerpc/opal-irqchip: Fix deadlock introduced by "Fix double endian conversion"
Commit 25642e1459ac ("powerpc/opal-irqchip: Fix double endian conversion") fixed an endian bug by calling opal_handle_events() in opal_event_unmask(). However this introduced a deadlock if we find an event is active during unmasking and call opal_handle_events() again. The bad call sequence is: opal_interrupt() -> opal_handle_events() -> generic_handle_irq() -> handle_level_irq() -> raw_spin_lock(&desc->lock) handle_irq_event(desc) unmask_irq(desc) -> opal_event_unmask() -> opal_handle_events() -> generic_handle_irq() -> handle_level_irq() -> raw_spin_lock(&desc->lock) (BOOM) When generating multiple opal events in quick succession this would lead to the following stall warnings: EEH: Fenced PHB#0 detected, location: U78C9.001.WZS09XA-P1-C32 INFO: rcu_sched detected stalls on CPUs/tasks: 12-...: (1 GPs behind) idle=68f/140000000000001/0 softirq=860/861 fqs=2065 15-...: (1 GPs behind) idle=be5/140000000000001/0 softirq=1142/1143 fqs=2065 (detected by 13, t=2102 jiffies, g=1325, c=1324, q=602) NMI watchdog: BUG: soft lockup - CPU#18 stuck for 22s! [irqbalance:2696] INFO: rcu_sched detected stalls on CPUs/tasks: 12-...: (1 GPs behind) idle=68f/140000000000001/0 softirq=860/861 fqs=8371 15-...: (1 GPs behind) idle=be5/140000000000001/0 softirq=1142/1143 fqs=8371 (detected by 20, t=8407 jiffies, g=1325, c=1324, q=1290) This patch corrects the problem by queuing the work if an event is active during unmasking, which is similar to the pre-endian fix behaviour. Fixes: 25642e1459ac ("powerpc/opal-irqchip: Fix double endian conversion") Signed-off-by: Alistair Popple <alistair@popple.id.au> Reported-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch')
-rw-r--r--arch/powerpc/platforms/powernv/opal-irqchip.c14
1 files changed, 13 insertions, 1 deletions
diff --git a/arch/powerpc/platforms/powernv/opal-irqchip.c b/arch/powerpc/platforms/powernv/opal-irqchip.c
index 0a00e2aed393..e505223b4ec5 100644
--- a/arch/powerpc/platforms/powernv/opal-irqchip.c
+++ b/arch/powerpc/platforms/powernv/opal-irqchip.c
@@ -83,7 +83,19 @@ static void opal_event_unmask(struct irq_data *d)
set_bit(d->hwirq, &opal_event_irqchip.mask);
opal_poll_events(&events);
- opal_handle_events(be64_to_cpu(events));
+ last_outstanding_events = be64_to_cpu(events);
+
+ /*
+ * We can't just handle the events now with opal_handle_events().
+ * If we did we would deadlock when opal_event_unmask() is called from
+ * handle_level_irq() with the irq descriptor lock held, because
+ * calling opal_handle_events() would call generic_handle_irq() and
+ * then handle_level_irq() which would try to take the descriptor lock
+ * again. Instead queue the events for later.
+ */
+ if (last_outstanding_events & opal_event_irqchip.mask)
+ /* Need to retrigger the interrupt */
+ irq_work_queue(&opal_event_irq_work);
}
static int opal_event_set_type(struct irq_data *d, unsigned int flow_type)