linux-kernel - Re: [PATCH v2 1/3] misc: pci_endpoint_test: Avoid issue of interrupts remaining after request

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Message-ID: <2cdb5e43-47e0-43ba-ba17-87e8d5dc602d@socionext.com>
Date: Wed, 29 Jan 2025 16:54:46 +0900
From: Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc: Krzysztof Wilczyński <kw@...ux.com>,
 Kishon Vijay Abraham I <kishon@...nel.org>, Arnd Bergmann <arnd@...db.de>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Lorenzo Pieralisi <lpieralisi@...nel.org>,
 Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
 Bjorn Helgaas <helgaas@...nel.org>, linux-pci@...r.kernel.org,
 linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v2 1/3] misc: pci_endpoint_test: Avoid issue of interrupts
 remaining after request_irq error

Hi Manivannan,

On 2025/01/28 23:12, Manivannan Sadhasivam wrote:
> On Wed, Jan 22, 2025 at 11:24:44AM +0900, Kunihiko Hayashi wrote:
>> After devm_request_irq() fails with error,
>> pci_endpoint_test_free_irq_vectors() is called to free allocated vectors
>> with pci_free_irq_vectors().
>>
> 
> You should mention the function name which you are referring to. Here it is,
> pci_endpoint_test_request_irq().

I see. I'll make the commit message more clear.

>> However some requested IRQs are still allocated, so there are still
> 
> This is confusing. Are you saying that the previously requested IRQs are not
> freed when an error happens during the for loop in
> pci_endpoint_test_request_irq()?

Yes, after jumping to "fail:" label, it just prints an error message and
returns the function.

The pci_endpoint_test_request_irq() is called from the following functions:
- pci_endpoint_test_probe()
- pci_endpoint_test_set_irq()

Both call pci_endpoint_test_free_irq_vectors() after the error, though,
requested IRQs are not freed anywhere.

>> /proc/irq/* entries remaining and we encounters WARN() with the following
>> message:
>>
>>      remove_proc_entry: removing non-empty directory 'irq/30', leaking at
>>      least 'pci-endpoint-test.0'
>>      WARNING: CPU: 0 PID: 80 at fs/proc/generic.c:717 remove_proc_entry
>>      +0x190/0x19c
> 
> When did you encounter this WARN?

Usually request_irq() can successfully get an interrupt.
If request_irq() returned an error, pci_endpoint_test_free_irq_vectors() was
called and the following call-trace was obtained:

[   18.772522] Call trace:
[   18.773743]  remove_proc_entry+0x190/0x19c
[   18.775789]  unregister_irq_proc+0xd0/0x104
[   18.777881]  free_desc+0x4c/0xcc
[   18.779495]  irq_free_descs+0x68/0x8c
[   18.781325]  irq_domain_free_irqs+0x15c/0x1bc
[   18.783502]  msi_domain_free_locked.part.0+0x184/0x1d4
[   18.786069]  msi_domain_free_irqs_all_locked+0x64/0x8c
[   18.788637]  pci_msi_teardown_msi_irqs+0x48/0x54
[   18.790947]  pci_free_msi_irqs+0x18/0x38
[   18.792907]  pci_free_irq_vectors+0x64/0x8c
[   18.794997]  pci_endpoint_test_ioctl+0x7e8/0xf40
[   18.797304]  __arm64_sys_ioctl+0xa4/0xe8
[   18.799265]  invoke_syscall+0x48/0x110
[   18.801139]  el0_svc_common.constprop.0+0x40/0xe8
[   18.803489]  do_el0_svc+0x20/0x2c
[   18.805145]  el0_svc+0x30/0xd0
[   18.806673]  el0t_64_sync_handler+0x13c/0x158
[   18.808850]  el0t_64_sync+0x190/0x194
[   18.810680] ---[ end trace 0000000000000000 ]---

>> To solve this issue, set the number of remaining IRQs and release the IRQs
>> in advance by calling pci_endpoint_test_release_irq().
>>
> 
> First of all, using devm_request_irq() is wrong here as
> pci_endpoint_test_request_irq() might be called multiple times by the userspace.
> So we cannot use managed version of request_irq(). It is infact pointless since
> pci_endpoint_test_clear_irq() would free them anyway. Instead we should just use
> request_irq() and call pci_endpoint_test_clear_irq() in the error path as like
> this patch does.

The pci_endpoint_test_clear_irq() will free all the number of IRQs.
However, in this error case, since only some IRQs are allocated, need to change the
number of IRQs that need to be freed.

And pci_endpoint_test_free_irq_vectors() is called just before return from the function,
call only pci_endpoint_test_release_irq() in the error case of
pci_endpoint_test_request_irq().

For example:
   pci_endpoint_test_set_irq()
     pci_endpoint_test_request_irq()
       request_irq()
       fail:
       >> test->num_irqs = i                // add in this patch
       >> pci_endpoint_test_release_irq()   // add in this patch
     err:
     pci_endpoint_test_free_irq_vectors()

> But this should be a separate patch.

Agreed. I'll add another patch to use non-managed version.

Thank you,

---
Best Regards
Kunihiko Hayashi