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    Subject[PATCH AUTOSEL 6.1 10/13] LoongArch: Only call get_timer_irq() once in constant_clockevent_init()
    Date
    From: Tiezhu Yang <yangtiezhu@loongson.cn>

    [ Upstream commit bb7a78e343468873bf00b2b181fcfd3c02d8cb56 ]

    Under CONFIG_DEBUG_ATOMIC_SLEEP=y and CONFIG_DEBUG_PREEMPT=y, we can see
    the following messages on LoongArch, this is because using might_sleep()
    in preemption disable context.

    [ 0.001127] smp: Bringing up secondary CPUs ...
    [ 0.001222] Booting CPU#1...
    [ 0.001244] 64-bit Loongson Processor probed (LA464 Core)
    [ 0.001247] CPU1 revision is: 0014c012 (Loongson-64bit)
    [ 0.001250] FPU1 revision is: 00000000
    [ 0.001252] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:283
    [ 0.001255] in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 0, name: swapper/1
    [ 0.001257] preempt_count: 1, expected: 0
    [ 0.001258] RCU nest depth: 0, expected: 0
    [ 0.001259] Preemption disabled at:
    [ 0.001261] [<9000000000223800>] arch_dup_task_struct+0x20/0x110
    [ 0.001272] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 6.2.0-rc7+ #43
    [ 0.001275] Hardware name: Loongson Loongson-3A5000-7A1000-1w-A2101/Loongson-LS3A5000-7A1000-1w-A2101, BIOS vUDK2018-LoongArch-V4.0.05132-beta10 12/13/202
    [ 0.001277] Stack : 0072617764726148 0000000000000000 9000000000222f1c 90000001001e0000
    [ 0.001286] 90000001001e3be0 90000001001e3be8 0000000000000000 0000000000000000
    [ 0.001292] 90000001001e3be8 0000000000000040 90000001001e3cb8 90000001001e3a50
    [ 0.001297] 9000000001642000 90000001001e3be8 be694d10ce4139dd 9000000100174500
    [ 0.001303] 0000000000000001 0000000000000001 00000000ffffe0a2 0000000000000020
    [ 0.001309] 000000000000002f 9000000001354116 00000000056b0000 ffffffffffffffff
    [ 0.001314] 0000000000000000 0000000000000000 90000000014f6e90 9000000001642000
    [ 0.001320] 900000000022b69c 0000000000000001 0000000000000000 9000000001736a90
    [ 0.001325] 9000000100038000 0000000000000000 9000000000222f34 0000000000000000
    [ 0.001331] 00000000000000b0 0000000000000004 0000000000000000 0000000000070000
    [ 0.001337] ...
    [ 0.001339] Call Trace:
    [ 0.001342] [<9000000000222f34>] show_stack+0x5c/0x180
    [ 0.001346] [<90000000010bdd80>] dump_stack_lvl+0x60/0x88
    [ 0.001352] [<9000000000266418>] __might_resched+0x180/0x1cc
    [ 0.001356] [<90000000010c742c>] mutex_lock+0x20/0x64
    [ 0.001359] [<90000000002a8ccc>] irq_find_matching_fwspec+0x48/0x124
    [ 0.001364] [<90000000002259c4>] constant_clockevent_init+0x68/0x204
    [ 0.001368] [<900000000022acf4>] start_secondary+0x40/0xa8
    [ 0.001371] [<90000000010c0124>] smpboot_entry+0x60/0x64

    Here are the complete call chains:

    smpboot_entry()
    start_secondary()
    constant_clockevent_init()
    get_timer_irq()
    irq_find_matching_fwnode()
    irq_find_matching_fwspec()
    mutex_lock()
    might_sleep()
    __might_sleep()
    __might_resched()

    In order to avoid the above issue, we should break the call chains,
    using timer_irq_installed variable as check condition to only call
    get_timer_irq() once in constant_clockevent_init() is a simple and
    proper way.

    Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
    Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/loongarch/kernel/time.c | 11 ++++++-----
    1 file changed, 6 insertions(+), 5 deletions(-)

    diff --git a/arch/loongarch/kernel/time.c b/arch/loongarch/kernel/time.c
    index 786735dcc8d67..d2b7d5df132a9 100644
    --- a/arch/loongarch/kernel/time.c
    +++ b/arch/loongarch/kernel/time.c
    @@ -135,16 +135,17 @@ static int get_timer_irq(void)

    int constant_clockevent_init(void)
    {
    - int irq;
    unsigned int cpu = smp_processor_id();
    unsigned long min_delta = 0x600;
    unsigned long max_delta = (1UL << 48) - 1;
    struct clock_event_device *cd;
    - static int timer_irq_installed = 0;
    + static int irq = 0, timer_irq_installed = 0;

    - irq = get_timer_irq();
    - if (irq < 0)
    - pr_err("Failed to map irq %d (timer)\n", irq);
    + if (!timer_irq_installed) {
    + irq = get_timer_irq();
    + if (irq < 0)
    + pr_err("Failed to map irq %d (timer)\n", irq);
    + }

    cd = &per_cpu(constant_clockevent_device, cpu);

    --
    2.39.2
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