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    Subject[PATCH AUTOSEL 4.14 06/46] um: change sigio_spinlock to a mutex
    Date
    From: Johannes Berg <johannes.berg@intel.com>

    [ Upstream commit f2d05059e15af3f70502074f4e3a504530af504a ]

    Lockdep complains at boot:

    =============================
    [ BUG: Invalid wait context ]
    5.7.0-05093-g46d91ecd597b #98 Not tainted
    -----------------------------
    swapper/1 is trying to lock:
    0000000060931b98 (&desc[i].request_mutex){+.+.}-{3:3}, at: __setup_irq+0x11d/0x623
    other info that might help us debug this:
    context-{4:4}
    1 lock held by swapper/1:
    #0: 000000006074fed8 (sigio_spinlock){+.+.}-{2:2}, at: sigio_lock+0x1a/0x1c
    stack backtrace:
    CPU: 0 PID: 1 Comm: swapper Not tainted 5.7.0-05093-g46d91ecd597b #98
    Stack:
    7fa4fab0 6028dfd1 0000002a 6008bea5
    7fa50700 7fa50040 7fa4fac0 6028e016
    7fa4fb50 6007f6da 60959c18 00000000
    Call Trace:
    [<60023a0e>] show_stack+0x13b/0x155
    [<6028e016>] dump_stack+0x2a/0x2c
    [<6007f6da>] __lock_acquire+0x515/0x15f2
    [<6007eb50>] lock_acquire+0x245/0x273
    [<6050d9f1>] __mutex_lock+0xbd/0x325
    [<6050dc76>] mutex_lock_nested+0x1d/0x1f
    [<6008e27e>] __setup_irq+0x11d/0x623
    [<6008e8ed>] request_threaded_irq+0x169/0x1a6
    [<60021eb0>] um_request_irq+0x1ee/0x24b
    [<600234ee>] write_sigio_irq+0x3b/0x76
    [<600383ca>] sigio_broken+0x146/0x2e4
    [<60020bd8>] do_one_initcall+0xde/0x281

    Because we hold sigio_spinlock and then get into requesting
    an interrupt with a mutex.

    Change the spinlock to a mutex to avoid that.

    Signed-off-by: Johannes Berg <johannes.berg@intel.com>
    Signed-off-by: Richard Weinberger <richard@nod.at>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/um/kernel/sigio.c | 6 +++---
    1 file changed, 3 insertions(+), 3 deletions(-)

    diff --git a/arch/um/kernel/sigio.c b/arch/um/kernel/sigio.c
    index b5e0cbb343828..476ded92affac 100644
    --- a/arch/um/kernel/sigio.c
    +++ b/arch/um/kernel/sigio.c
    @@ -36,14 +36,14 @@ int write_sigio_irq(int fd)
    }

    /* These are called from os-Linux/sigio.c to protect its pollfds arrays. */
    -static DEFINE_SPINLOCK(sigio_spinlock);
    +static DEFINE_MUTEX(sigio_mutex);

    void sigio_lock(void)
    {
    - spin_lock(&sigio_spinlock);
    + mutex_lock(&sigio_mutex);
    }

    void sigio_unlock(void)
    {
    - spin_unlock(&sigio_spinlock);
    + mutex_unlock(&sigio_mutex);
    }
    --
    2.25.1
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