• Qi Liu's avatar
    drivers/perf: Fix kernel panic when rmmod PMU modules during perf sampling · bdc5c744
    Qi Liu authored
    When users try to remove PMU modules during perf sampling, kernel panic
    will happen because the pmu->read() is a NULL pointer here.
    
    INFO on HiSilicon hip08 platform as follow:
    pc : hisi_uncore_pmu_event_update+0x30/0xa4 [hisi_uncore_pmu]
    lr : hisi_uncore_pmu_read+0x20/0x2c [hisi_uncore_pmu]
    sp : ffff800010103e90
    x29: ffff800010103e90 x28: ffff0027db0c0e40
    x27: ffffa29a76f129d8 x26: ffffa29a77ceb000
    x25: ffffa29a773a5000 x24: ffffa29a77392000
    x23: ffffddffe5943f08 x22: ffff002784285960
    x21: ffff002784285800 x20: ffff0027d2e76c80
    x19: ffff0027842859e0 x18: ffff80003498bcc8
    x17: ffffa29a76afe910 x16: ffffa29a7583f530
    x15: 16151a1512061a1e x14: 0000000000000000
    x13: ffffa29a76f1e238 x12: 0000000000000001
    x11: 0000000000000400 x10: 00000000000009f0
    x9 : ffff8000107b3e70 x8 : ffff0027db0c1890
    x7 : ffffa29a773a7000 x6 : 00000007f5131013
    x5 : 00000007f5131013 x4 : 09f257d417c00000
    x3 : 00000002187bd7ce x2 : ffffa29a38f0f0d8
    x1 : ffffa29a38eae268 x0 : ffff0027d2e76c80
    Call trace:
    hisi_uncore_pmu_event_update+0x30/0xa4 [hisi_uncore_pmu]
    hisi_uncore_pmu_read+0x20/0x2c [hisi_uncore_pmu]
    __perf_event_read+0x1a0/0x1f8
    flush_smp_call_function_queue+0xa0/0x160
    generic_smp_call_function_single_interrupt+0x18/0x20
    handle_IPI+0x31c/0x4dc
    gic_handle_irq+0x2c8/0x310
    el1_irq+0xcc/0x180
    arch_cpu_idle+0x4c/0x20c
    default_idle_call+0x20/0x30
    do_idle+0x1b4/0x270
    cpu_startup_entry+0x28/0x30
    secondary_start_kernel+0x1a4/0x1fc
    
    To solve the above issue, current module should be registered to kernel,
    so that try_module_get() can be invoked when perf sampling starts. This
    adds the reference counting of module and could prevent users from removing
    modules during sampling.
    Reported-by: default avatarHaifeng Wang <wang.wanghaifeng@huawei.com>
    Signed-off-by: default avatarQi Liu <liuqi115@huawei.com>
    Reviewed-by: default avatarJohn Garry <john.garry@huawei.com>
    Link: https://lore.kernel.org/r/1594891165-8228-1-git-send-email-liuqi115@huawei.comSigned-off-by: default avatarWill Deacon <will@kernel.org>
    bdc5c744
fsl_imx8_ddr_perf.c 18.2 KB