Messages in this thread | | | Date | Thu, 16 Jul 2020 11:44:22 +0100 | From | Will Deacon <> | Subject | Re: [PATCH] drivers/perf: Fix kernel panic when rmmod PMU modules during perf sampling |
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On Thu, Jul 16, 2020 at 11:36:10AM +0100, John Garry wrote: > On 16/07/2020 11:30, Will Deacon wrote: > > On Thu, Jul 16, 2020 at 11:26:25AM +0100, Robin Murphy wrote: > > > On 2020-07-16 10:41, Will Deacon wrote: > > > > On Thu, Jul 16, 2020 at 05:19:25PM +0800, Qi Liu wrote: > > > > > Kernel panic will also happen when users try to unbind PMU drivers with > > > > > device. This unbind issue could be solved by another patch latter. > > > > > > > > > > drivers/perf/arm_smmuv3_pmu.c | 1 + > > > > > drivers/perf/fsl_imx8_ddr_perf.c | 1 + > > > > > drivers/perf/hisilicon/hisi_uncore_ddrc_pmu.c | 1 + > > > > > drivers/perf/hisilicon/hisi_uncore_hha_pmu.c | 1 + > > > > > drivers/perf/hisilicon/hisi_uncore_l3c_pmu.c | 1 + > > > > > 5 files changed, 5 insertions(+) > > > > > > > > > > diff --git a/drivers/perf/arm_smmuv3_pmu.c b/drivers/perf/arm_smmuv3_pmu.c > > > > > index 48e28ef..90caba56 100644 > > > > > --- a/drivers/perf/arm_smmuv3_pmu.c > > > > > +++ b/drivers/perf/arm_smmuv3_pmu.c > > > > > @@ -742,6 +742,7 @@ static int smmu_pmu_probe(struct platform_device *pdev) > > > > > platform_set_drvdata(pdev, smmu_pmu); > > > > > > > > > > smmu_pmu->pmu = (struct pmu) { > > > > > + .module = THIS_MODULE, > > > > I thought platform_driver_register() did this automatically? > > > For the platform device itself, yes, but this is for the PMU device - perf > > > needs to take a reference to the module, otherwise the platform device can > > > still be pulled out from under its feet. > > Urgh, gross. > > > > > I can't remember if we ever discussed making perf_pmu_register() do the same > > > trick as platform_device_register() and friends, but obviously it's a > > > possibility. > > Yeah, but I suppose this patch is the right thing to do for now. I'll queue > > it as a fix. > > > > Please also note what Qi Liu wrote about being able to unbind the driver and > cause the same issue. I don't know if you can about that issue also.
I guess we have to throw in some '.suppress_bind_attrs = true,' lines as well, then? I'll queue this as-is, but happy to take a follow-up if somebody can test it.
Will
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