With lockdep support implemented on CRISv32, we get the following splat.
switch_mm() can be called both from the scheduler() (with interrupts
disabled) and from flush_old_exec (via activate_mm()), with interrupts
enabled. Fix it by disabling interrupts in activate_mm(), similar to
powerpc and hexagon.
t======================================================
[ INFO: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected ]
3.19.0-08802-g20bc9f1-dirty #323 Not tainted
------------------------------------------------------
init/1 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
(mmu_context_lock){+.+...}, at: [<c0009290>] switch_mm+0x22/0xc6
and this task is already holding:
(&rq->lock){-.-.-.}, at: [<c01a0756>] __schedule+0x5e/0x648
which would create a new lock dependency:
(&rq->lock){-.-.-.} -> (mmu_context_lock){+.+...}
but this new dependency connects a HARDIRQ-irq-safe lock:
(&rq->lock){-.-.-.}
... which became HARDIRQ-irq-safe at:
[<c002b03c>] scheduler_tick+0x28/0x5e
[<c0007c6c>] timer_interrupt+0x4e/0x6a
[<c0043ac4>] handle_irq_event_percpu+0x54/0x13c
[<c004343c>] generic_handle_irq+0x2a/0x36
to a HARDIRQ-irq-unsafe lock:
(mmu_context_lock){+.+...}
... which became HARDIRQ-irq-unsafe at:
... [<c0039e60>] __lock_acquire+0x8f8/0x1d9c
[<c0009290>] switch_mm+0x22/0xc6
[<c009c260>] flush_old_exec+0x500/0x5d4
[<c00da4c6>] load_elf_phdrs+0x7a/0x84
[<c00dbdb0>] load_elf_binary+0x21c/0x13b4
[<c009cdb6>] do_execve+0x22/0x2c
[<c001dcf2>] ____call_usermodehelper+0x0/0x154
[<c000581e>] ret_from_kernel_thread+0xe/0x14
other info that might help us debug this:
Possible interrupt unsafe locking scenario:
CPU0 CPU1
---- ----
lock(mmu_context_lock);
local_irq_disable();
lock(&rq->lock);
lock(mmu_context_lock);
<Interrupt>
lock(&rq->lock);
*** DEADLOCK ***
1 lock held by init/1:
#0: (&rq->lock){-.-.-.}, at: [<c01a0756>] __schedule+0x5e/0x648
Call Trace:
[<c019fe9e>] printk+0x0/0x4e
[<c00368f8>] print_shortest_lock_dependencies+0x0/0x15c
[<c0048628>] print_stack_trace+0x0/0x88
[<c0038912>] __lock_is_held+0x3e/0x5e
[<c003b894>] lock_acquire+0x8a/0xcc
[<c01a50c4>] _raw_spin_lock+0x44/0x7a
[<c0009290>] switch_mm+0x22/0xc6
[<c01a06f8>] __schedule+0x0/0x648
[<c01a0d76>] schedule+0x36/0x7c
[<c0037d04>] trace_hardirqs_on+0x0/0x1e
[<c0004e18>] do_work_pending+0x30/0xd4
[<c000591a>] _work_pending+0xe/0x12
Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Jesper Nilsson <jesper.nilsson@axis.com>
7f0144e777