[PATCH] x86_64: fix vector_lock deadlock in io_apic.c

Fix a potential deadlock scenario introduced by io_apic.c's new vector_lock
on i386 and x86_64.

Found by the locking correctness validator. The patch was boot-tested on
x86. For details of the deadlock scenario, see the validator output:

  ======================================================
  [ BUG: hard-safe -> hard-unsafe lock order detected! ]
  ------------------------------------------------------
  idle/1 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
   (msi_lock){....}, at: [<c04ff8d2>] startup_msi_irq_wo_maskbit+0x10/0x35

  and this task is already holding:
   (&irq_desc[i].lock){++..}, at: [<c015b924>] probe_irq_on+0x36/0x107
  which would create a new lock dependency:
   (&irq_desc[i].lock){++..} -> (msi_lock){....}

  but this new dependency connects a hard-irq-safe lock:
   (&irq_desc[i].lock){++..}
  ... which became hard-irq-safe at:
    [<c01468c4>] lockdep_acquire+0x68/0x84
    [<c10485e9>] _spin_lock+0x21/0x2f
    [<c015aff5>] __do_IRQ+0x3d/0x113
    [<c01062d3>] do_IRQ+0x8c/0xad

  to a hard-irq-unsafe lock:
   (vector_lock){--..}
  ... which became hard-irq-unsafe at:
  ...  [<c01468c4>] lockdep_acquire+0x68/0x84
    [<c10485e9>] _spin_lock+0x21/0x2f
    [<c011b5e8>] assign_irq_vector+0x34/0xc8
    [<c1aa82fa>] setup_IO_APIC+0x45a/0xcff
    [<c1aa56e3>] smp_prepare_cpus+0x5ea/0x8aa
    [<c010033f>] init+0x32/0x2cb
    [<c0102005>] kernel_thread_helper+0x5/0xb

  which could potentially lead to deadlocks!

  other info that might help us debug this:

  3 locks held by idle/1:
   #0:  (port_mutex){--..}, at: [<c067070d>] uart_add_one_port+0x61/0x289
   #1:  (&state->mutex){--..}, at: [<c067071f>] uart_add_one_port+0x73/0x289
   #2:  (&irq_desc[i].lock){++..}, at: [<c015b924>] probe_irq_on+0x36/0x107

  the hard-irq-safe lock's dependencies:
  -> (&irq_desc[i].lock){++..} ops: 9861 {
     initial-use  at:
                          [<c01468c4>] lockdep_acquire+0x68/0x84
                          [<c10487f4>] _spin_lock_irqsave+0x2a/0x3a
                          [<c015b415>] setup_irq+0x9b/0x14d
                          [<c1aaa4c4>] time_init_hook+0xf/0x11
                          [<c1a9f320>] time_init+0x44/0x46
                          [<c1a9955f>] start_kernel+0x191/0x38f
                          [<c0100210>] 0xc0100210
     in-hardirq-W at:
                          [<c01468c4>] lockdep_acquire+0x68/0x84
                          [<c10485e9>] _spin_lock+0x21/0x2f
                          [<c015aff5>] __do_IRQ+0x3d/0x113
                          [<c01062d3>] do_IRQ+0x8c/0xad
     in-softirq-W at:
                          [<c01468c4>] lockdep_acquire+0x68/0x84
                          [<c10485e9>] _spin_lock+0x21/0x2f
                          [<c015aff5>] __do_IRQ+0x3d/0x113
                          [<c01062d3>] do_IRQ+0x8c/0xad
   }
   ... key      at: [<c1ea31e0>] irq_desc_lock_type+0x0/0x20
    -> (i8259A_lock){++..} ops: 5149 {
       initial-use  at:
                        [<c01468c4>] lockdep_acquire+0x68/0x84
                        [<c10487f4>] _spin_lock_irqsave+0x2a/0x3a
                        [<c0108090>] init_8259A+0x11/0x8f
                        [<c1aa0d22>] init_ISA_irqs+0x12/0x4d
                        [<c1aaa4f0>] pre_intr_init_hook+0x8/0xa
                        [<c1aa0cb9>] init_IRQ+0xe/0x65
                        [<c1a99546>] start_kernel+0x178/0x38f
                        [<c0100210>] 0xc0100210
       in-hardirq-W at:
                        [<c01468c4>] lockdep_acquire+0x68/0x84
                        [<c10487f4>] _spin_lock_irqsave+0x2a/0x3a
                        [<c0107fb0>] mask_and_ack_8259A+0x1b/0xcc
                        [<c015b007>] __do_IRQ+0x4f/0x113
                        [<c01062d3>] do_IRQ+0x8c/0xad
       in-softirq-W at:
                        [<c01468c4>] lockdep_acquire+0x68/0x84
                        [<c10487f4>] _spin_lock_irqsave+0x2a/0x3a
                        [<c0107fb0>] mask_and_ack_8259A+0x1b/0xcc
                        [<c015b007>] __do_IRQ+0x4f/0x113
                        [<c01062d3>] do_IRQ+0x8c/0xad
     }
     ... key      at: [<c142f174>] i8259A_lock+0x14/0x40
   ... acquired at:
     [<c01468c4>] lockdep_acquire+0x68/0x84
     [<c10487f4>] _spin_lock_irqsave+0x2a/0x3a
     [<c0107eb2>] enable_8259A_irq+0x10/0x47
     [<c0107f12>] startup_8259A_irq+0x8/0xc
     [<c015b45e>] setup_irq+0xe4/0x14d
     [<c1aaa4c4>] time_init_hook+0xf/0x11
     [<c1a9f320>] time_init+0x44/0x46
     [<c1a9955f>] start_kernel+0x191/0x38f
     [<c0100210>] 0xc0100210

    -> (ioapic_lock){+...} ops: 122 {
       initial-use  at:
                        [<c01468c4>] lockdep_acquire+0x68/0x84
                        [<c10487f4>] _spin_lock_irqsave+0x2a/0x3a
                        [<c1aa71db>] io_apic_get_version+0x16/0x55
                        [<c1aa5c73>] mp_register_ioapic+0xc6/0x127
                        [<c1aa382e>] acpi_parse_ioapic+0x2d/0x39
                        [<c1abe031>] acpi_table_parse_madt_family+0xb4/0x100
                        [<c1abe093>] acpi_table_parse_madt+0x16/0x18
                        [<c1aa3c8a>] acpi_boot_init+0x132/0x251
                        [<c1aa08ea>] setup_arch+0xd36/0xe37
                        [<c1a99434>] start_kernel+0x66/0x38f
                        [<c0100210>] 0xc0100210
       in-hardirq-W at:
                        [<c01468c4>] lockdep_acquire+0x68/0x84
                        [<c10487f4>] _spin_lock_irqsave+0x2a/0x3a
                        [<c011bce1>] mask_IO_APIC_irq+0x11/0x31
                        [<c011c5cc>] ack_edge_ioapic_vector+0x31/0x41
                        [<c015b007>] __do_IRQ+0x4f/0x113
                        [<c01062d3>] do_IRQ+0x8c/0xad
     }
     ... key      at: [<c1432514>] ioapic_lock+0x14/0x3c
      -> (i8259A_lock){++..} ops: 5149 {
         initial-use  at:
                         [<c01468c4>] lockdep_acquire+0x68/0x84
                         [<c10487f4>] _spin_lock_irqsave+0x2a/0x3a
                         [<c0108090>] init_8259A+0x11/0x8f
                         [<c1aa0d22>] init_ISA_irqs+0x12/0x4d
                         [<c1aaa4f0>] pre_intr_init_hook+0x8/0xa
                         [<c1aa0cb9>] init_IRQ+0xe/0x65
                         [<c1a99546>] start_kernel+0x178/0x38f
                         [<c0100210>] 0xc0100210
         in-hardirq-W at:
                         [<c01468c4>] lockdep_acquire+0x68/0x84
                         [<c10487f4>] _spin_lock_irqsave+0x2a/0x3a
                         [<c0107fb0>] mask_and_ack_8259A+0x1b/0xcc
                         [<c015b007>] __do_IRQ+0x4f/0x113
                         [<c01062d3>] do_IRQ+0x8c/0xad
         in-softirq-W at:
                         [<c01468c4>] lockdep_acquire+0x68/0x84
                         [<c10487f4>] _spin_lock_irqsave+0x2a/0x3a
                         [<c0107fb0>] mask_and_ack_8259A+0x1b/0xcc
                         [<c015b007>] __do_IRQ+0x4f/0x113
                         [<c01062d3>] do_IRQ+0x8c/0xad
       }
       ... key      at: [<c142f174>] i8259A_lock+0x14/0x40
     ... acquired at:
     [<c01468c4>] lockdep_acquire+0x68/0x84
     [<c10487f4>] _spin_lock_irqsave+0x2a/0x3a
     [<c0107e6b>] disable_8259A_irq+0x10/0x47
     [<c011bdbd>] startup_edge_ioapic_vector+0x31/0x58
     [<c015b45e>] setup_irq+0xe4/0x14d
     [<c015b5a1>] request_irq+0xda/0xf9
     [<c1ac983a>] rtc_init+0x6a/0x1a7
     [<c0100457>] init+0x14a/0x2cb
     [<c0102005>] kernel_thread_helper+0x5/0xb

   ... acquired at:
     [<c01468c4>] lockdep_acquire+0x68/0x84
     [<c10487f4>] _spin_lock_irqsave+0x2a/0x3a
     [<c011bce1>] mask_IO_APIC_irq+0x11/0x31
     [<c011c5cc>] ack_edge_ioapic_vector+0x31/0x41
     [<c015b007>] __do_IRQ+0x4f/0x113
     [<c01062d3>] do_IRQ+0x8c/0xad

  the hard-irq-unsafe lock's dependencies:
  -> (vector_lock){--..} ops: 31 {
     initial-use  at:
                          [<c01468c4>] lockdep_acquire+0x68/0x84
                          [<c10485e9>] _spin_lock+0x21/0x2f
                          [<c011b5e8>] assign_irq_vector+0x34/0xc8
                          [<c1aa82fa>] setup_IO_APIC+0x45a/0xcff
                          [<c1aa56e3>] smp_prepare_cpus+0x5ea/0x8aa
                          [<c010033f>] init+0x32/0x2cb
                          [<c0102005>] kernel_thread_helper+0x5/0xb
     softirq-on-W at:
                          [<c01468c4>] lockdep_acquire+0x68/0x84
                          [<c10485e9>] _spin_lock+0x21/0x2f
                          [<c011b5e8>] assign_irq_vector+0x34/0xc8
                          [<c1aa82fa>] setup_IO_APIC+0x45a/0xcff
                          [<c1aa56e3>] smp_prepare_cpus+0x5ea/0x8aa
                          [<c010033f>] init+0x32/0x2cb
                          [<c0102005>] kernel_thread_helper+0x5/0xb
     hardirq-on-W at:
                          [<c01468c4>] lockdep_acquire+0x68/0x84
                          [<c10485e9>] _spin_lock+0x21/0x2f
                          [<c011b5e8>] assign_irq_vector+0x34/0xc8
                          [<c1aa82fa>] setup_IO_APIC+0x45a/0xcff
                          [<c1aa56e3>] smp_prepare_cpus+0x5ea/0x8aa
                          [<c010033f>] init+0x32/0x2cb
                          [<c0102005>] kernel_thread_helper+0x5/0xb
   }
   ... key      at: [<c1432574>] vector_lock+0x14/0x3c

  stack backtrace:
   [<c0104f36>] show_trace+0xd/0xf
   [<c010543e>] dump_stack+0x17/0x19
   [<c0144e34>] check_usage+0x1f6/0x203
   [<c0146395>] __lockdep_acquire+0x8c2/0xaa5
   [<c01468c4>] lockdep_acquire+0x68/0x84
   [<c10487f4>] _spin_lock_irqsave+0x2a/0x3a
   [<c04ff8d2>] startup_msi_irq_wo_maskbit+0x10/0x35
   [<c015b932>] probe_irq_on+0x44/0x107
   [<c0673d58>] serial8250_config_port+0x84b/0x986
   [<c06707b1>] uart_add_one_port+0x105/0x289
   [<c1ace54b>] serial8250_init+0xc3/0x10a
   [<c0100457>] init+0x14a/0x2cb
   [<c0102005>] kernel_thread_helper+0x5/0xb

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Jan Beulich <jbeulich@novell.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/kernel/io_apic.c

@@ -1163,14 +1163,15 @@ u8 irq_vector[NR_IRQ_VECTORS] __read_mostly = { FIRST_DEVICE_VECTOR , 0 };
 int assign_irq_vector(int irq)
 {
 	static int current_vector = FIRST_DEVICE_VECTOR, offset = 0;
+	unsigned long flags;
 	int vector;
 
 	BUG_ON(irq != AUTO_ASSIGN && (unsigned)irq >= NR_IRQ_VECTORS);
 
-	spin_lock(&vector_lock);
+	spin_lock_irqsave(&vector_lock, flags);
 
 	if (irq != AUTO_ASSIGN && IO_APIC_VECTOR(irq) > 0) {
-		spin_unlock(&vector_lock);
+		spin_unlock_irqrestore(&vector_lock, flags);
 		return IO_APIC_VECTOR(irq);
 	}
 next:
@@ -1181,7 +1182,7 @@ next:
 	if (current_vector >= FIRST_SYSTEM_VECTOR) {
 		offset++;
 		if (!(offset%8)) {
-			spin_unlock(&vector_lock);
+			spin_unlock_irqrestore(&vector_lock, flags);
 			return -ENOSPC;
 		}
 		current_vector = FIRST_DEVICE_VECTOR + offset;
@@ -1192,7 +1193,7 @@ next:
 	if (irq != AUTO_ASSIGN)
 		IO_APIC_VECTOR(irq) = vector;
 
-	spin_unlock(&vector_lock);
+	spin_unlock_irqrestore(&vector_lock, flags);
 
 	return vector;
 }

arch/x86_64/kernel/io_apic.c

@@ -836,14 +836,15 @@ u8 irq_vector[NR_IRQ_VECTORS] __read_mostly = { FIRST_DEVICE_VECTOR , 0 };
 int assign_irq_vector(int irq)
 {
 	static int current_vector = FIRST_DEVICE_VECTOR, offset = 0;
+	unsigned long flags;
 	int vector;
 
 	BUG_ON(irq != AUTO_ASSIGN && (unsigned)irq >= NR_IRQ_VECTORS);
 
-	spin_lock(&vector_lock);
+	spin_lock_irqsave(&vector_lock, flags);
 
 	if (irq != AUTO_ASSIGN && IO_APIC_VECTOR(irq) > 0) {
-		spin_unlock(&vector_lock);
+		spin_unlock_irqrestore(&vector_lock, flags);
 		return IO_APIC_VECTOR(irq);
 	}
 next:
@@ -862,7 +863,7 @@ next:
 	if (irq != AUTO_ASSIGN)
 		IO_APIC_VECTOR(irq) = vector;
 
-	spin_unlock(&vector_lock);
+	spin_unlock_irqrestore(&vector_lock, flags);
 
 	return vector;
 }