[patch, -rc5-mm3] fix IDE deadlock in error reporting code

[Ingo Molnar <mingo@elte.hu>]

* Michal Piotrowski <michal.k.k.piotrowski@gmail.com> wrote:

> >i've uploaded a fixed version - does that work for you?
> 
> Yes, thanks.
> 
> Here is dmesg 
> http://www.stardust.webpages.pl/files/mm/2.6.17-rc5-mm3/mm-dmesg
> Here is latency trace
> http://www.stardust.webpages.pl/files/mm/2.6.17-rc5-mm3/mm-latency.bz2
> Here is config 
> http://www.stardust.webpages.pl/files/mm/2.6.17-rc5-mm3/mm-config
> 
> Here is something new
> Jun  4 23:59:44 ltg01-fedora kernel: hdd: set_drive_speed_status:
> status=0x51 { DriveReady SeekComplete Error }
> Jun  4 23:59:44 ltg01-fedora kernel: hdd: set_drive_speed_status:
> error=0xb4 { AbortedCommand LastFailedSense=0x0b }
> Jun  4 23:59:44 ltg01-fedora kernel: (          hdparm-1821 |#0): new
> 164424143 us user-latency.
> Jun  4 23:59:44 ltg01-fedora kernel: stopped custom tracer.
> Jun  4 23:59:44 ltg01-fedora kernel:
> Jun  4 23:59:44 ltg01-fedora kernel: ============================
> Jun  4 23:59:44 ltg01-fedora kernel: [ BUG: illegal lock usage! ]
> Jun  4 23:59:44 ltg01-fedora kernel: ----------------------------
> Jun  4 23:59:44 ltg01-fedora kernel: illegal {in-hardirq-W} ->
> {hardirq-on-W} usage.
> Jun  4 23:59:44 ltg01-fedora kernel: hdparm/1821 [HC0[0]:SC0[0]:HE1:SE1] 
> takes:
> Jun  4 23:59:44 ltg01-fedora kernel:  (ide_lock){++..}, at:
> [<c0268388>] ide_dump_opcode+0x13/0x9b

ah. That's a real deadlock scenario. Does the patch below fix it? If yes 
then i think this is a candidate for 2.6.17 merging too.

	Ingo

--------------------------
Subject: [patch, -rc5-mm3] fix IDE deadlock in error reporting code
From: Ingo Molnar <mingo@elte.hu>

Michal Piotrowski reported the following validator assert:

 hdd: set_drive_speed_status: status=0x51 { DriveReady SeekComplete Error }
 hdd: set_drive_speed_status: error=0xb4 { AbortedCommand LastFailedSense=0x0b }

 ============================
 [ BUG: illegal lock usage! ]
 ----------------------------
 illegal {in-hardirq-W} -> {hardirq-on-W} usage.
 hdparm/1821 [HC0[0]:SC0[0]:HE1:SE1] takes:
  (ide_lock){++..}, at: [<c0268388>] ide_dump_opcode+0x13/0x9b

 [...]

 stack backtrace:
  [<c0104513>] show_trace+0x1b/0x20
  [<c01045f1>] dump_stack+0x1f/0x24
  [<c013976c>] print_usage_bug+0x1a5/0x1b1
  [<c0139e90>] mark_lock+0x2ca/0x4f7
  [<c013aa96>] __lockdep_acquire+0x47e/0xaa4
  [<c013b536>] lockdep_acquire+0x67/0x7f
  [<c030552d>] _spin_lock+0x24/0x32
  [<c0268388>] ide_dump_opcode+0x13/0x9b
  [<c02688b6>] ide_dump_status+0x4a6/0x4cc
  [<c0267ae6>] ide_config_drive_speed+0x32a/0x33a
  [<c0262dc5>] piix_tune_chipset+0x2ed/0x2f8
  [<c0262e31>] piix_config_drive_xfer_rate+0x61/0xb5
  [<c0263a82>] set_using_dma+0x2f/0x60
  [<c0263bee>] ide_write_setting+0x4a/0xc3
  [<c02647ca>] generic_ide_ioctl+0x8a/0x47f
  [<f886003a>] idecd_ioctl+0xfd/0x133 [ide_cd]
  [<c01f1fff>] blkdev_driver_ioctl+0x4b/0x5f
  [<c01f2783>] blkdev_ioctl+0x770/0x7bd
  [<c017dc0d>] block_ioctl+0x1f/0x21
  [<c0189353>] do_ioctl+0x27/0x6e
  [<c0189604>] vfs_ioctl+0x26a/0x280
  [<c0189667>] sys_ioctl+0x4d/0x7e
  [<c0305ed2>] sysenter_past_esp+0x63/0xa1

in ide_dump_opcode() takes the ide_lock in an irq-unsafe manner,
i.e. this function expects to be called with irqs disabled. But
ide_dump_ata[pi]_status() doesnt do that - it enables interrupts
specifically. That is a no-no - what guarantees that another IDE
port couldnt generate an IDE interrupt while we are dumping this
error? The fix is to turn the irq-enabling in these functions into
irq-disabling.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 drivers/ide/ide-lib.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Index: linux/drivers/ide/ide-lib.c
===================================================================
--- linux.orig/drivers/ide/ide-lib.c
+++ linux/drivers/ide/ide-lib.c
@@ -506,7 +506,7 @@ static u8 ide_dump_ata_status(ide_drive_
 	unsigned long flags;
 	u8 err = 0;
 
-	local_irq_set(flags);
+	local_irq_save(flags);
 	printk("%s: %s: status=0x%02x { ", drive->name, msg, stat);
 	if (stat & BUSY_STAT)
 		printk("Busy ");
@@ -588,7 +588,7 @@ static u8 ide_dump_atapi_status(ide_driv
 
 	status.all = stat;
 	error.all = 0;
-	local_irq_set(flags);
+	local_irq_save(flags);
 	printk("%s: %s: status=0x%02x { ", drive->name, msg, stat);
 	if (status.b.bsy)
 		printk("Busy ");
-
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