Re: powerpc/opal-irqchip: Fix deadlock introduced by "Fix double endian conversion"

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 <redacted>
Reported-by: Andrew Donnellan <redacted>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/036592fbbe753d236402a0ae68

cheers