Messages in this thread | | | Date | Sat, 28 Jan 2023 20:20:56 +0800 | Subject | Re: [PATCH v2 3/8] iommu: Add lockdep annotations for group list iterators | From | Baolu Lu <> |
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On 2023/1/27 2:26, Robin Murphy wrote: > Before we add any more common helpers for iterating or otherwise > accessing the group device list, let's start the good habit of > annotating their locking expectations for robustness. > > Signed-off-by: Robin Murphy <robin.murphy@arm.com> > --- > > v2: New. Note that I've left the group_pasid helpers, since they're > pretty much right next to where the relevant locking happens, and > highly unlikely to be reused from anywhere else anyway. > > drivers/iommu/iommu.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > index d48e5499e0fa..77f076030995 100644 > --- a/drivers/iommu/iommu.c > +++ b/drivers/iommu/iommu.c > @@ -20,6 +20,7 @@ > #include <linux/iommu.h> > #include <linux/idr.h> > #include <linux/err.h> > +#include <linux/lockdep.h> > #include <linux/pci.h> > #include <linux/pci-ats.h> > #include <linux/bitops.h> > @@ -1100,6 +1101,7 @@ static int iommu_group_device_count(struct iommu_group *group) > struct group_device *entry; > int ret = 0; > > + lockdep_assert_held(&group->mutex); > list_for_each_entry(entry, &group->devices, list) > ret++; > > @@ -1112,6 +1114,7 @@ static int __iommu_group_for_each_dev(struct iommu_group *group, void *data, > struct group_device *device; > int ret = 0; > > + lockdep_assert_held(&group->mutex);
When I tested this patch on an Intel platform, I found that the bus_iommu_probe() path iterates the group device list but does not hold the lock.
1831 static void __iommu_group_dma_finalize(struct iommu_group *group) 1832 { 1833 __iommu_group_for_each_dev(group, group->default_domain, 1834 iommu_group_do_probe_finalize); 1835 }
bus_iommu_probe:
1873 /* Try to allocate default domain */ 1874 probe_alloc_default_domain(group); 1875 1876 if (!group->default_domain) { 1877 mutex_unlock(&group->mutex); 1878 continue; 1879 } 1880 1881 iommu_group_create_direct_mappings(group); 1882 1883 ret = __iommu_group_dma_first_attach(group); 1884 1885 mutex_unlock(&group->mutex); 1886 1887 if (ret) 1888 break; 1889 1890 __iommu_group_dma_finalize(group);
The lockdep_assert_held() caused below kernel trace:
[ 70.022590] ------------[ cut here ]------------ [ 70.027967] WARNING: CPU: 1 PID: 1 at drivers/iommu/iommu.c:1135 __iommu_group_for_each_dev+0x72/0x80 [ 70.038672] Modules linked in: [ 70.042264] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G W 6.2.0-rc5+ #421 [ 70.063860] RIP: 0010:__iommu_group_for_each_dev+0x72/0x80 [ 70.070267] Code: 5c 41 5d c3 cc cc cc cc 5b 31 c0 5d 41 5c 41 5d c3 cc cc cc cc 48 8d bf 10 01 00 00 be ff ff ff ff e8 92 7b 8f 00 85 c0 75 ac <0f> 0b eb a8 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 [ 70.091981] RSP: 0000:ffffad104006fd30 EFLAGS: 00010246 [ 70.098058] RAX: 0000000000000000 RBX: ffff9f490bb95600 RCX: 0000000000000001 [ 70.106378] RDX: 0000000000000001 RSI: ffff9f490bb95710 RDI: ffff9f4900b10d88 [ 70.114674] RBP: ffff9f490bb95600 R08: ffffcd26844fde80 R09: ffffcd26844fde40 [ 70.122970] R10: 0000000000000000 R11: 0000000000000000 R12: ffff9f490bb95ed0 [ 70.131265] R13: ffffffff8aadd520 R14: ffffffff8aade3a0 R15: 0000000000000000 [ 70.139561] FS: 0000000000000000(0000) GS:ffff9f583ff00000(0000) knlGS:0000000000000000 [ 70.148969] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 70.155667] CR2: 0000000000000000 CR3: 0000000cc2012001 CR4: 0000000000370ee0 [ 70.163963] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 70.172282] DR3: 0000000000000000 DR6: 00000000ffff07f0 DR7: 0000000000000400 [ 70.180559] Call Trace: [ 70.183469] <TASK> [ 70.185972] bus_iommu_probe+0xee/0x1e0 [ 70.190496] iommu_device_register+0xaf/0x100 [ 70.195580] intel_iommu_init+0x3e9/0x6f2 [ 70.200271] ? __pfx_pci_iommu_init+0x10/0x10 [ 70.205381] ? __pfx_ignore_unknown_bootoption+0x10/0x10 [ 70.211564] pci_iommu_init+0x12/0x3a [ 70.215870] do_one_initcall+0x65/0x330 [ 70.220376] ? __pfx_ignore_unknown_bootoption+0x10/0x10 [ 70.226577] ? rcu_read_lock_sched_held+0x5a/0x80 [ 70.232076] kernel_init_freeable+0x287/0x2f0 [ 70.237914] ? __pfx_kernel_init+0x10/0x10 [ 70.241979] kernel_init+0x1a/0x130 [ 70.246075] ret_from_fork+0x29/0x50 [ 70.251014] </TASK> [ 70.252867] irq event stamp: 16350051 [ 70.257167] hardirqs last enabled at (16350061): [<ffffffff8a1c3ed2>] __up_console_sem+0x52/0x60 [ 70.267468] hardirqs last disabled at (16350070): [<ffffffff8a1c3eb7>] __up_console_sem+0x37/0x60 [ 70.277768] softirqs last enabled at (16350006): [<ffffffff8b3edd03>] __do_softirq+0x283/0x451 [ 70.287859] softirqs last disabled at (16350001): [<ffffffff8a132c6a>] irq_exit_rcu+0xaa/0xc0 [ 70.297777] ---[ end trace 0000000000000000 ]---
> list_for_each_entry(device, &group->devices, list) { > ret = fn(device->dev, data); > if (ret)
Best regards, baolu
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