linux-kernel - Re: [PATCH] cxl/pmu: Ensure put

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Date:   Mon, 16 Oct 2023 16:43:27 -0700
From:   Dave Jiang <dave.jiang@...el.com>
To:     Ira Weiny <ira.weiny@...el.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Jonathan Cameron <jonathan.cameron@...wei.com>,
        Alison Schofield <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        "Dan Williams" <dan.j.williams@...el.com>
CC:     <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cxl/pmu: Ensure put_device on pmu devices



On 10/16/23 16:25, Ira Weiny wrote:
> The following kmemleaks were detected when removing the cxl module
> stack:
> 
> unreferenced object 0xffff88822616b800 (size 1024):
> ...
>   backtrace:
>     [<00000000bedc6f83>] kmalloc_trace+0x26/0x90
>     [<00000000448d1afc>] devm_cxl_pmu_add+0x3a/0x110 [cxl_core]
>     [<00000000ca3bfe16>] 0xffffffffa105213b
>     [<00000000ba7f78dc>] local_pci_probe+0x41/0x90
>     [<000000005bb027ac>] pci_device_probe+0xb0/0x1c0
> ...
> unreferenced object 0xffff8882260abcc0 (size 16):
> ...
>   hex dump (first 16 bytes):
>     70 6d 75 5f 6d 65 6d 30 2e 30 00 26 82 88 ff ff  pmu_mem0.0.&....
>   backtrace:
> ...
>     [<00000000152b5e98>] dev_set_name+0x43/0x50
>     [<00000000c228798b>] devm_cxl_pmu_add+0x102/0x110 [cxl_core]
>     [<00000000ca3bfe16>] 0xffffffffa105213b
>     [<00000000ba7f78dc>] local_pci_probe+0x41/0x90
>     [<000000005bb027ac>] pci_device_probe+0xb0/0x1c0
> ...
> unreferenced object 0xffff8882272af200 (size 256):
> ...
>   backtrace:
>     [<00000000bedc6f83>] kmalloc_trace+0x26/0x90
>     [<00000000a14d1813>] device_add+0x4ea/0x890
>     [<00000000a3f07b47>] devm_cxl_pmu_add+0xbe/0x110 [cxl_core]
>     [<00000000ca3bfe16>] 0xffffffffa105213b
>     [<00000000ba7f78dc>] local_pci_probe+0x41/0x90
>     [<000000005bb027ac>] pci_device_probe+0xb0/0x1c0
> ...
> 
> devm_cxl_pmu_add() correctly registers a device remove function but it
> only calls device_del() which is only part of device unregistration.
> 
> Properly call device_unregister() to free up the memory associated with
> the device.
> 
> Fixes: 1ad3f701c399 ("cxl/pci: Find and register CXL PMU devices")
> Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Signed-off-by: Ira Weiny <ira.weiny@...el.com>

Reviewed-by: Dave Jiang <dave.jiang@...el.com>

Although I wonder if we can just give device_unregister() to devm_add_action_or_reset() directly. 

> ---
>  drivers/cxl/core/pmu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/cxl/core/pmu.c b/drivers/cxl/core/pmu.c
> index 7684c843e5a5..5d8e06b0ba6e 100644
> --- a/drivers/cxl/core/pmu.c
> +++ b/drivers/cxl/core/pmu.c
> @@ -23,7 +23,7 @@ const struct device_type cxl_pmu_type = {
>  
>  static void remove_dev(void *dev)
>  {
> -	device_del(dev);
> +	device_unregister(dev);
>  }
>  
>  int devm_cxl_pmu_add(struct device *parent, struct cxl_pmu_regs *regs,
> 
> ---
> base-commit: 58720809f52779dc0f08e53e54b014209d13eebb
> change-id: 20231016-pmu-unregister-fix-345480926a58
> 
> Best regards,