Messages in this thread | | | Date | Sat, 02 Mar 2024 19:48:53 +0000 | From | Edmund Raile <> | Subject | Re: [PATCH v2] firewire: ohci: prevent leak of left-over IRQ on unbind |
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> In my opinion, the devres mechanism releases the allocated memory when > releasing the data of associated device structure. > device_release_driver_internal() > ->__device_release_driver() > ->device_unbind_cleanup() > (drivers/base/devres.c) > ->devres_release_all(dev); > ->release_nodes() > (kernel/irq/devres.c) > ->free_irq()
Looking at __device_release_driver() in drivers/base/dd.c, device_remove() gets called, leading to dev->bus->remove(dev), which likely calls our good old friend from the call trace: pci_device_remove().
> > Call Trace: > > ? remove_proc_entry+0x19c/0x1c0 > > ? __warn+0x81/0x130 > > ? remove_proc_entry+0x19c/0x1c0 > > ? report_bug+0x171/0x1a0 > > ? console_unlock+0x78/0x120 > > ? handle_bug+0x3c/0x80 > > ? exc_invalid_op+0x17/0x70 > > ? asm_exc_invalid_op+0x1a/0x20 > > ? remove_proc_entry+0x19c/0x1c0 > > unregister_irq_proc+0xf4/0x120 > > free_desc+0x3d/0xe0 > > ? kfree+0x29f/0x2f0 > > irq_free_descs+0x47/0x70 > > msi_domain_free_locked.part.0+0x19d/0x1d0 > > msi_domain_free_irqs_all_locked+0x81/0xc0 > > pci_free_msi_irqs+0x12/0x40 > > pci_disable_msi+0x4c/0x60 > > pci_remove+0x9d/0xc0 [firewire_ohci > > 01b483699bebf9cb07a3d69df0aa2bee71db1b26] > > pci_device_remove+0x37/0xa0 > > device_release_driver_internal+0x19f/0x200 > > unbind_store+0xa1/0xb0
Then in ohci.c's pci_remove(), we kill the MSIs, which leads to the removal of the IRQ, etc. Back in __device_release_driver(), after device_remove(), device_unbind_cleanup() is called, leading to free_irq(), but too late.
I think the order of these calls may be our issue but I doubt it has been done like this without good reason. That code is 8 years old, someone would have noticed if it had an error.
I could be entirely wrong but the function description in /kernel/irq/devres.c tells me that function is meant to be used:
> Except for the extra @dev argument, this function takes the > same arguments and performs the same function as free_irq(). > This function instead of free_irq() should be used to manually > free IRQs allocated with devm_request_irq().
And while devm_request_irq() has no function description of its own, its sister devm_request_threaded_irq() mentions this:
> IRQs requested with this function will be > automatically freed on driver detach. > > If an IRQ allocated with this function needs to be freed > separately, devm_free_irq() must be used.
Should we pull in the maintainers of dd.c for their opinion?
Thank you very much for all the very hard work you do Sakamoto-Sensei!
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