On Tue, Feb 11, 2025 at 01:09:04AM +0530, Anand Moon wrote: > Hi Manivannan > > On Mon, 10 Feb 2025 at 23:14, Manivannan Sadhasivam > <manivannan.sadhasivam@xxxxxxxxxx> wrote: > > > > On Sat, Feb 08, 2025 at 07:31:08PM +0530, Anand Moon wrote: > > > kmemleak reported following debug log > > > > > > $ sudo cat /sys/kernel/debug/kmemleak > > > unreferenced object 0xffffffd6c47c2600 (size 128): > > > comm "kworker/u16:2", pid 38, jiffies 4294942263 > > > hex dump (first 32 bytes): > > > cc 7c 5a 8d ff ff ff ff 40 b0 47 c8 d6 ff ff ff .|Z.....@.G..... > > > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > > > backtrace (crc 4f07ff07): > > > __create_object+0x2a/0xfc > > > kmemleak_alloc+0x38/0x98 > > > __kmalloc_cache_noprof+0x296/0x444 > > > request_threaded_irq+0x168/0x284 > > > devm_request_threaded_irq+0xa8/0x13c > > > plda_init_interrupts+0x46e/0x858 > > > plda_pcie_host_init+0x356/0x468 > > > starfive_pcie_probe+0x2f6/0x398 > > > platform_probe+0x106/0x150 > > > really_probe+0x30e/0x746 > > > __driver_probe_device+0x11c/0x2c2 > > > driver_probe_device+0x5e/0x316 > > > __device_attach_driver+0x296/0x3a4 > > > bus_for_each_drv+0x1d0/0x260 > > > __device_attach+0x1fa/0x2d6 > > > device_initial_probe+0x14/0x28 > > > unreferenced object 0xffffffd6c47c2900 (size 128): > > > comm "kworker/u16:2", pid 38, jiffies 4294942281 > > > > > > This patch addresses a kmemleak reported during StarFive PCIe driver > > > initialization. The leak was observed with kmemleak reporting > > > unreferenced objects related to IRQ handling. The backtrace pointed > > > to the `request_threaded_irq` and related functions within the > > > `plda_init_interrupts` path, indicating that some allocated memory > > > related to IRQs was not being properly freed. > > > > > > The issue was that while the driver requested IRQs, it wasn't > > > correctly handling the lifecycle of the associated resources. > > > > What resources? > > > The Microchip PCIe host driver [1] handles PCI, SEC, DEBUG, and LOCAL > hardware events > through a dedicated framework [2]. This framework allows the core driver [3] > to monitor and wait for these specific events. > Microchip driver also has its own 'event_ops' and 'event_irq_chip', so defining 'request_event_irq()' callback makes sense to me. > [1]: https://github.com/torvalds/linux/blob/master/drivers/pci/controller/plda/pcie-microchip-host.c#L90-L292 > [2]: https://github.com/torvalds/linux/blob/master/drivers/pci/controller/plda/pcie-microchip-host.c#L374-L499 > [3]: https://github.com/torvalds/linux/blob/master/drivers/pci/controller/plda/pcie-plda-host.c#L448-L466 > > StarFive PCIe driver currently lacks the necessary `request_event_irq` > implementation > to integrate with this event-handling mechanism, which prevents the core driver > from properly responding to these events on StarFive platforms. > > static const struct plda_event mc_event = { > . request_event_irq = mc_request_event_irq, > .intx_event = EVENT_LOCAL_PM_MSI_INT_INTX, > .msi_event = EVENT_LOCAL_PM_MSI_INT_MSI, > }; > > This patch implements dummy `request_event_irq` for the StarFive PCIe driver, > Since the core [3] driver is monitoring for these events > This still doesn't make sense to me. Under what condition you observed the kmemleak? Since it points to devm_request_irq(), I can understand that the memory allocated for the IRQ is not freed. But when does it happen? > > > This patch introduces an event IRQ handler and the necessary > > > infrastructure to manage these IRQs, preventing the memory leak. > > > > > > > These handles appear pointless to me. What purpose are they serving? > > > Yes, you are correct, the core event monitoring framework [3] triggered a > kernel memory leak. This patch adds a dummy IRQ callback as a > placeholder for proper event handling, which can be implemented in a > future patch. > The dummy request_event_irq() callback is not supposed to be needed in the first place. So clearly, this patch is not fixing the actual memory leak but trying to cover it up. - Mani -- மணிவண்ணன் சதாசிவம்
