| Message ID | 1450419377-29847-1-git-send-email-alistair@popple.id.au (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
On Fri, 2015-18-12 at 06:16:17 UTC, Alistair Popple wrote: > Commit 25642e1459ac ("powerpc/opal-irqchip: Fix double endian > conversion") fixed an endian bug by calling opal_handle_events() in > opal_event_unmask(). However this introduces a deadlock when an event > is active during unmasking as opal_handle_events() calls > generic_handle_irq() which may call opal_event_unmask() with the irq > descriptor lock held. > > 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. > > Signed-off-by: Alistair Popple <alistair@popple.id.au> > Reported-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com> Applied to powerpc fixes, thanks. https://git.kernel.org/powerpc/c/036592fbbe753d236402a0ae68 cheers
diff --git a/arch/powerpc/platforms/powernv/opal-irqchip.c b/arch/powerpc/platforms/powernv/opal-irqchip.c index 0a00e2a..2f12cb9 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() as opal_event_unmask() gets called + * from generic_handle_irq() which holds the irq descriptor + * lock leading to a deadlock if generic_handle_irq() gets + * called again from opal_handle_events(). 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)
Commit 25642e1459ac ("powerpc/opal-irqchip: Fix double endian conversion") fixed an endian bug by calling opal_handle_events() in opal_event_unmask(). However this introduces a deadlock when an event is active during unmasking as opal_handle_events() calls generic_handle_irq() which may call opal_event_unmask() with the irq descriptor lock held. 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. Signed-off-by: Alistair Popple <alistair@popple.id.au> Reported-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com> Cc: stable@vger.kernel.org --- Michael, I'm quite confident this fixes the problem as it is just reverting to the previous behaviour only with the endian corrected, which was really the correct fix in the first place. Thanks. arch/powerpc/platforms/powernv/opal-irqchip.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) -- 2.1.4