Re: [PATCH 2/3] sparc64: convert spinlock_t to raw_spinlock_t inmmu_context_t

[Allen Pais]

>> Issue debugged by Thomas Gleixner <tglx@xxxxxxxxxxxxx>
The kernel crashed while I attempted preempt_rt support on log
at:

[ 1487.027884] I7: <rt_mutex_setprio+0x3c/0x2c0>
[ 1487.027885] Call Trace:
[ 1487.027887]  [00000000004967dc] rt_mutex_setprio+0x3c/0x2c0
[ 1487.027892]  [00000000004afe20] task_blocks_on_rt_mutex+0x180/0x200
[ 1487.027895]  [0000000000819114] rt_spin_lock_slowlock+0x94/0x300
[ 1487.027897]  [0000000000817ebc] __schedule+0x39c/0x53c
[ 1487.027899]  [00000000008185fc] schedule+0x1c/0xc0
[ 1487.027908]  [000000000048fff4] smpboot_thread_fn+0x154/0x2e0
[ 1487.027913]  [000000000048753c] kthread+0x7c/0xa0
[ 1487.027920]  [00000000004060c4] ret_from_syscall+0x1c/0x2c
[ 1487.027922]  [0000000000000000]           (null)

Thomas debugged it and pointed me towards the fix.

> 
> I think davem would appreciate if you add a little here than this. The
> same goes for 3/3.
> 

The same goes with 3/3

[ 2317.606015]  [00000000008072f4] rt_spin_lock_slowlock+0x94/0x300
[ 2317.606020]  [0000000000451d74] get_new_mmu_context+0x14/0x160
[ 2317.606026]  [0000000000806394] switch_to_pc+0xd4/0x2a0
[ 2317.606029]  [00000000008067dc] schedule+0x1c/0xc0
[ 2317.606031]  [0000000000807364] rt_spin_lock_slowlock+0x104/0x300
[ 2317.606033]  [0000000000450284] destroy_context+0x84/0x120
[ 2317.606036]  [000000000045c788] __mmdrop+0x28/0xe0
[ 2317.606045]  [00000000004bf290] rcu_process_callbacks+0x450/0x760
[ 2317.606049]  [0000000000466d48] do_current_softirqs+0x208/0x3c0
[ 2317.606051]  [0000000000466f14] run_ksoftirqd+0x14/0x40
[ 2317.606057]  [000000000048c64c] smpboot_thread_fn+0x18c/0x2e0
[ 2317.606061]  [0000000000483b5c] kthread+0x7c/0xa0
[ 2317.606069]  [00000000004060c4] ret_from_syscall+0x1c/0x2c
[ 2317.606070]  [0000000000000000]           (null)

I am not sure if it'd be nice to put the call trace in the commit message.
But if needed I can re-send them.

- Allen
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