Re: [PATCH 2/2] coresight: core: Fix multiple free TRBE platform data resource

[hejunhao <hejunhao3@huawei.com>]

Hi, Suzuki


On 2023/8/15 6:47, Suzuki K Poulose wrote:
> + James Clark
>
> On 14/08/2023 10:38, Junhao He wrote:
>> Current the TRBE driver supports matching TRBE platform device through
>> id_table. The ACPI created a dummy TRBE platform device inside
>> drivers/perf/arm_pmu_acpi.c. So the TRBE platform driver will probe only
>> once and allocate just one TRBE platform data resource.
>>
>> If the system supports the TRBE feature, Each CPU in the systems can
>> have at least one TRBE present, and the coresight_unregister gets called
>> multiple times, once for each of them.
>> Therefore, when unregister TRBE coresight devices, the TRBE platform 
>> data
>> resource will multiple free in function coresight_unregister.
>>
>> root@localhost:# insmod coresight-trbe.ko
>> root@localhost:# rmmod coresight-trbe.ko
>> [  423.455932] ------------[ cut here ]------------
>> [  423.461987] WARNING: CPU: 1 PID: 0 at drivers/base/devres.c:1064 
>> devm_kfree+0x88/0x98
>> [  423.483821] CPU: 1 PID: 0 Comm: swapper/1 Tainted: G           
>> O       6.5.0-rc4+ #1
>> [  423.505842] pstate: 614000c9 (nZCv daIF +PAN -UAO -TCO +DIT -SSBS 
>> BTYPE=--)
>> ...
>> [  423.601301] Call trace:
>> [  423.604202]  devm_kfree+0x88/0x98
>> [  423.608369]  coresight_release_platform_data+0xb8/0xe0 [coresight]
>> [  423.616589]  coresight_unregister+0x120/0x170 [coresight]
>> [  423.623533]  arm_trbe_remove_coresight_cpu+0x70/0xa0 [coresight_trbe]
>> [  423.631082]  __flush_smp_call_function_queue+0x1e4/0x4e0
>> [  423.637471] generic_smp_call_function_single_interrupt+0x1c/0x30
>> [  423.644796]  ipi_handler+0x90/0x278
>> [  423.648992]  handle_percpu_devid_irq+0x90/0x250
>> [  423.654636]  generic_handle_domain_irq+0x34/0x58
>> [  423.659786]  gic_handle_irq+0x12c/0x270
>> [  423.664039]  call_on_irq_stack+0x24/0x30
>> [  423.668452]  do_interrupt_handler+0x88/0x98
>> [  423.673027]  el1_interrupt+0x48/0xe8
>> [  423.677413]  el1h_64_irq_handler+0x18/0x28
>> [  423.681781]  el1h_64_irq+0x78/0x80
>> [  423.685550]  default_idle_call+0x5c/0x180
>> [  423.689855]  do_idle+0x25c/0x2c0
>> [  423.694196]  cpu_startup_entry+0x2c/0x40
>> [  423.698373]  secondary_start_kernel+0x144/0x188
>> [  423.703920]  __secondary_switched+0xb8/0xc0
>> [  423.708972] ---[ end trace 0000000000000000 ]---
>> [  423.729209] ------------[ cut here ]------------
>> ...
>> [  423.735217] WARNING: CPU: 2 PID: 40 at drivers/base/devres.c:1064 
>> devm_kfree+0x88/0x98
>> ...
>> [  424.012385] WARNING: CPU: 3 PID: 0 at drivers/base/devres.c:1064 
>> devm_kfree+0x88/0x98
>> ...
>>
>> This patch does the following:
>> 1.TRBE coresight devices do not need regular connections information, We
>>    can free connections resource when the nr_conns is valid.
>> 2.And we can ignore the free platform data resource, it will be
>>    automatically free in platform_driver_unregister().
>
> Do we need a Fixes tag here ?

Yes, I will do that.

>>
>> Signed-off-by: Junhao He <hejunhao3@huawei.com>
>> ---
>>   drivers/hwtracing/coresight/coresight-core.c | 7 ++++---
>>   1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-core.c 
>> b/drivers/hwtracing/coresight/coresight-core.c
>> index 118fcf27854d..c6f7889d1b4d 100644
>> --- a/drivers/hwtracing/coresight/coresight-core.c
>> +++ b/drivers/hwtracing/coresight/coresight-core.c
>> @@ -1555,9 +1555,10 @@ void coresight_release_platform_data(struct 
>> coresight_device *csdev,
>>           conns[i]->dest_fwnode = NULL;
>>           devm_kfree(dev, conns[i]);
>>       }
>> -    devm_kfree(dev, pdata->out_conns);
>> -    devm_kfree(dev, pdata->in_conns);
>> -    devm_kfree(dev, pdata);
>> +    if (pdata->nr_outconns)
>> +        devm_kfree(dev, pdata->out_conns);
>> +    if (pdata->nr_inconns)
>> +        devm_kfree(dev, pdata->in_conns);
>
> These allocations are made on the parent device and that
> may never get unregistered (e.g., AMBA device, platform device,
> stay forever, even when the "coresight" modules are unloaded).
> Thus the memory will be left unused, literally leaking.
> This specific devm_kfree() was added to fix that. May be we should fix
> this in the TRBE driver to use separate pdata for the TRBE device
> instances.
>
> Suzuki

If we fix this with minimal changes, I think it is possible to add a check
and not free pdata if it is TRBE?

     if (csdev->subtype.sink_subtype != 
CORESIGHT_DEV_SUBTYPE_SINK_PERCPU_SYSMEM)
         devm_kfree(dev, pdata);

Then free pdata in the end of arm_trbe_remove_coresight().

>
>>       if (csdev)
>>           coresight_remove_conns_sysfs_group(csdev);
>>   }
>
>
> .
>