Re: [PATCH v2 00/10] Refine the locking for dev->iommu_group
From: Marek Szyprowski <m.szyprowski@samsung.com>
Date: 2023-08-08 13:01:23
Also in:
linux-iommu, linux-rockchip, linux-sunxi
Hi All, On 08.08.2023 14:32, Marek Szyprowski wrote:
On 08.08.2023 12:31, Chen-Yu Tsai wrote:quoted
On Mon, Aug 7, 2023 at 8:54 PM Joerg Roedel [off-list ref] wrote:quoted
On Mon, Jul 31, 2023 at 02:50:23PM -0300, Jason Gunthorpe wrote:quoted
Jason Gunthorpe (10): iommu: Remove useless group refcounting iommu: Add a lockdep assertion for remaining dev->iommu_group reads iommu: Add generic_single_device_group() iommu/sun50i: Convert to generic_single_device_group() iommu/sprd: Convert to generic_single_device_group() iommu/rockchip: Convert to generic_single_device_group() iommu/ipmmu-vmsa: Convert to generic_single_device_group() iommu/omap: Convert to generic_single_device_group() iommu: Complete the locking for dev->iommu_group iommu/intel: Fix missing locking for show_device_domain_translation() drivers/iommu/intel/debugfs.c | 34 ++++---- drivers/iommu/iommu.c | 155 +++++++++++++++++++++------------ drivers/iommu/ipmmu-vmsa.c | 22 ++--- drivers/iommu/omap-iommu.c | 30 +------ drivers/iommu/omap-iommu.h | 2 +- drivers/iommu/rockchip-iommu.c | 22 +---- drivers/iommu/sprd-iommu.c | 24 +---- drivers/iommu/sun50i-iommu.c | 29 ++---- include/linux/iommu.h | 3 + 9 files changed, 138 insertions(+), 183 deletions(-)Applied, thanks for the nice cleanup!This series seems to cause a hung task during boot on MediaTek platforms. It hangs with next-20230808. Reverting the 10 commits from this series makes the system boot up again.I confirm that next-20230808 is broken on ARM 32bit based Exynos boards too. Boards lock up very early during boot. I will try to investigate this soon.
Hmm this turned to be Exynos IOMMU specific, but the issue is probably somehow generic. The deadlock happens early in __iommu_probe_device() on device_lock(dev). Here is a stack dump of that call: CPU: 1 PID: 1 Comm: swapper/0 Not tainted 6.5.0-rc5-next-20230808-dirty #7013 Hardware name: Samsung Exynos (Flattened Device Tree) unwind_backtrace from show_stack+0x10/0x14 show_stack from dump_stack_lvl+0x58/0x70 dump_stack_lvl from __iommu_probe_device+0x3d8/0x4ac __iommu_probe_device from probe_iommu_group+0x8/0x14 probe_iommu_group from bus_for_each_dev+0x60/0xb4 bus_for_each_dev from bus_iommu_probe+0x34/0x118 bus_iommu_probe from iommu_device_register+0x98/0x100 iommu_device_register from exynos_sysmmu_probe+0x238/0x3c0 exynos_sysmmu_probe from platform_probe+0x80/0xc0 platform_probe from really_probe+0x154/0x3d4 really_probe from __driver_probe_device+0xa0/0x1e8 __driver_probe_device from driver_probe_device+0x30/0xd0 driver_probe_device from __device_attach_driver+0xbc/0x11c __device_attach_driver from bus_for_each_drv+0x74/0xc0 bus_for_each_drv from __device_attach+0xec/0x1b4 __device_attach from bus_probe_device+0x8c/0x90 bus_probe_device from device_add+0x5b8/0x78c device_add from of_platform_device_create_pdata+0x94/0xcc of_platform_device_create_pdata from of_platform_bus_create+0x1ac/0x4d8 of_platform_bus_create from of_platform_bus_create+0x214/0x4d8 of_platform_bus_create from of_platform_populate+0x80/0x114 of_platform_populate from of_platform_default_populate_init+0xcc/0xe4 of_platform_default_populate_init from do_one_initcall+0x6c/0x318 do_one_initcall from kernel_init_freeable+0x1c4/0x214 kernel_init_freeable from kernel_init+0x18/0x12c kernel_init from ret_from_fork+0x14/0x2c The problem here is that exynos_sysmmu_probe() is by design called under device_lock, then it calls iommu_device_register(), which in turn triggers calling __iommu_probe_device() on all platform devices in the system, while the still probed sysmmu device is one of them. Frankly speaking I have no idea how to defer calling iommu_device_register() to avoid this deadlock. Any ideas? Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel