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authorQian Cai <cai@redhat.com>2020-10-28 11:27:17 -0400
committerMichael Ellerman <mpe@ellerman.id.au>2020-11-02 12:54:20 +1100
commitfd552e0542b4532483289cce48fdbd27b692984b (patch)
treecb8c7d78cc69a8cf448e5a3e6c441177011ad1a3 /arch
parent3cea11cd5e3b00d91caf0b4730194039b45c5891 (diff)
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powerpc/eeh_cache: Fix a possible debugfs deadlock
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
Diffstat (limited to 'arch')
-rw-r--r--arch/powerpc/kernel/eeh_cache.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/arch/powerpc/kernel/eeh_cache.c b/arch/powerpc/kernel/eeh_cache.c
index 6b50bf15d8c1..bf3270426d82 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;
}