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Alistair Popple 036592fbbe powerpc/opal-irqchip: Fix deadlock introduced by "Fix double endian conversion" 
Commit 25642e1459 ("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: 25642e1459 ("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>
2015-12-18 22:24:15 +11:00
..
boot powerpc/sbc8641: drop bogus PHY IRQ entries from DTS file 2015-12-09 14:00:39 +11:00
configs powerpc updates for 4.4 2015-11-05 23:38:43 -08:00
crypto crypto: powerpc/md5 - use md5 IV MD5_HX instead of their raw value 2015-05-18 12:20:20 +08:00
include Partial revert of "powerpc: Individual System V IPC system calls" 2015-12-16 21:52:32 +11:00
kernel Revert "powerpc/eeh: Don't unfreeze PHB PE after reset" 2015-12-09 14:05:10 +11:00
kvm Four changes: 2015-11-12 14:34:06 -08:00
lib powerpc32: memset: only use dcbz once cache is enabled 2015-09-17 10:36:53 +10:00
math-emu
mm powerpc updates for 4.4 2015-11-05 23:38:43 -08:00
net ebpf: migrate bpf_prog's flags to bitfield 2015-10-03 05:02:39 -07:00
oprofile powerpc: Remove mtmsrd(), use existing mtmsr() 2015-07-13 15:47:28 +10:00
perf powerpc updates for 4.4 2015-11-05 23:38:43 -08:00
platforms powerpc/opal-irqchip: Fix deadlock introduced by "Fix double endian conversion" 2015-12-18 22:24:15 +11:00
sysdev Merge branch 'for-4.4/io-poll' of git://git.kernel.dk/linux-block 2015-11-10 17:23:49 -08:00
xmon powerpc/xmon: Add some more elements to the existing PACA dump list 2015-10-15 20:32:02 +11:00
Kconfig powerpc/book3e-64: Enable kexec 2015-10-27 18:13:30 -05:00
Kconfig.debug powerpc: Make STRICT_MM_TYPECHECKS a config option 2015-05-11 19:53:59 +10:00
Makefile powerpc/cell: Drop CONFIG_TUNE_CELL in favour of CONFIG_CELL_CPU 2015-10-19 19:51:18 +11:00
relocs_check.sh powerpc: Convert relocs_check to a shell script using grep 2015-03-23 14:47:39 +11:00