| From 0311b13aa594f40bbc05ccadaac241fdec20726c Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Wed, 28 Oct 2020 11:27:17 -0400 |
| Subject: powerpc/eeh_cache: Fix a possible debugfs deadlock |
| |
| From: Qian Cai <cai@redhat.com> |
| |
| [ Upstream commit fd552e0542b4532483289cce48fdbd27b692984b ] |
| |
| Lockdep complains that a possible deadlock below in |
| eeh_addr_cache_show() because it is acquiring a lock with IRQ enabled, |
| but eeh_addr_cache_insert_dev() needs to acquire the same lock with IRQ |
| disabled. Let's just make eeh_addr_cache_show() acquire the lock with |
| IRQ disabled as well. |
| |
| CPU0 CPU1 |
| ---- ---- |
| lock(&pci_io_addr_cache_root.piar_lock); |
| local_irq_disable(); |
| lock(&tp->lock); |
| lock(&pci_io_addr_cache_root.piar_lock); |
| <Interrupt> |
| lock(&tp->lock); |
| |
| *** DEADLOCK *** |
| |
| lock_acquire+0x140/0x5f0 |
| _raw_spin_lock_irqsave+0x64/0xb0 |
| eeh_addr_cache_insert_dev+0x48/0x390 |
| eeh_probe_device+0xb8/0x1a0 |
| pnv_pcibios_bus_add_device+0x3c/0x80 |
| pcibios_bus_add_device+0x118/0x290 |
| pci_bus_add_device+0x28/0xe0 |
| pci_bus_add_devices+0x54/0xb0 |
| pcibios_init+0xc4/0x124 |
| do_one_initcall+0xac/0x528 |
| kernel_init_freeable+0x35c/0x3fc |
| kernel_init+0x24/0x148 |
| ret_from_kernel_thread+0x5c/0x80 |
| |
| lock_acquire+0x140/0x5f0 |
| _raw_spin_lock+0x4c/0x70 |
| eeh_addr_cache_show+0x38/0x110 |
| seq_read+0x1a0/0x660 |
| vfs_read+0xc8/0x1f0 |
| ksys_read+0x74/0x130 |
| system_call_exception+0xf8/0x1d0 |
| system_call_common+0xe8/0x218 |
| |
| Fixes: 5ca85ae6318d ("powerpc/eeh_cache: Add a way to dump the EEH address cache") |
| Signed-off-by: Qian Cai <cai@redhat.com> |
| Reviewed-by: Oliver O'Halloran <oohall@gmail.com> |
| Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> |
| Link: https://lore.kernel.org/r/20201028152717.8967-1-cai@redhat.com |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| arch/powerpc/kernel/eeh_cache.c | 5 +++-- |
| 1 file changed, 3 insertions(+), 2 deletions(-) |
| |
| diff --git a/arch/powerpc/kernel/eeh_cache.c b/arch/powerpc/kernel/eeh_cache.c |
| index 6b50bf15d8c19..bf3270426d82d 100644 |
| --- a/arch/powerpc/kernel/eeh_cache.c |
| +++ b/arch/powerpc/kernel/eeh_cache.c |
| @@ -264,8 +264,9 @@ static int eeh_addr_cache_show(struct seq_file *s, void *v) |
| { |
| struct pci_io_addr_range *piar; |
| struct rb_node *n; |
| + unsigned long flags; |
| |
| - spin_lock(&pci_io_addr_cache_root.piar_lock); |
| + spin_lock_irqsave(&pci_io_addr_cache_root.piar_lock, flags); |
| for (n = rb_first(&pci_io_addr_cache_root.rb_root); n; n = rb_next(n)) { |
| piar = rb_entry(n, struct pci_io_addr_range, rb_node); |
| |
| @@ -273,7 +274,7 @@ static int eeh_addr_cache_show(struct seq_file *s, void *v) |
| (piar->flags & IORESOURCE_IO) ? "i/o" : "mem", |
| &piar->addr_lo, &piar->addr_hi, pci_name(piar->pcidev)); |
| } |
| - spin_unlock(&pci_io_addr_cache_root.piar_lock); |
| + spin_unlock_irqrestore(&pci_io_addr_cache_root.piar_lock, flags); |
| |
| return 0; |
| } |
| -- |
| 2.27.0 |
| |
