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SubjectRe: sata_mv port lockup on hotplug (kernel 2.6.38.2)
On 11-04-12 06:30 AM, Bruce Stenning wrote:
..
> I am currently inserting tracing into 2.6.38.2 to try to work out what is going
> on. From mv_write_main_irq_mask I can see that the IRQ for each port is still
> enabled, even when ports stop responding.
..
> One thing I noticed was that there is no spinlock around the
> mv_save_cached_regs/mv_edma_cfg in mv_hardreset (unlike mv_port_start and
> mv_port_stop); why is this?

Yeah, I'm suspecting there's a loophole in the logic there somewhere.

I dusted off the 6041 reference card I have here, and played with the cables
for a while. Managed to get one port to stop responding to hot plug fairly
quickly, though I'm not sure how/why.

Then I added a debug printk() to mv_write_main_irq_mask(),
with no other changes, and that appears to have been enough
to change the race timing so that I could no longer produce
the problem.

Bruce, here's a slightly-ugly patch that should remove all
doubt about races in the irq_mask. Please apply it, test with it,
and let me know here if the issue goes away.

Thanks

--- old/drivers/ata/sata_mv.c 2011-04-13 11:03:07.442481426 -0400
+++ linux/drivers/ata/sata_mv.c 2011-04-13 11:07:55.224249621 -0400
@@ -1027,15 +1027,19 @@
static void mv_set_main_irq_mask(struct ata_host *host,
u32 disable_bits, u32 enable_bits)
{
+ static spinlock_t irq_mask_lock = __SPIN_LOCK_UNLOCKED(irq_mask_lock); //
FIXME: per-host would be nicer
struct mv_host_priv *hpriv = host->private_data;
u32 old_mask, new_mask;
+ unsigned long flags;

+ spin_lock_irqsave(&irq_mask_lock, flags);
old_mask = hpriv->main_irq_mask;
new_mask = (old_mask & ~disable_bits) | enable_bits;
if (new_mask != old_mask) {
hpriv->main_irq_mask = new_mask;
mv_write_main_irq_mask(new_mask, hpriv);
}
+ spin_unlock_irqrestore(&irq_mask_lock, flags);
}

static void mv_enable_port_irqs(struct ata_port *ap,--- old/drivers/ata/sata_mv.c 2011-04-13 11:03:07.442481426 -0400
+++ linux/drivers/ata/sata_mv.c 2011-04-13 11:07:55.224249621 -0400
@@ -1027,15 +1027,19 @@
static void mv_set_main_irq_mask(struct ata_host *host,
u32 disable_bits, u32 enable_bits)
{
+ static spinlock_t irq_mask_lock = __SPIN_LOCK_UNLOCKED(irq_mask_lock); // FIXME: per-host would be nicer
struct mv_host_priv *hpriv = host->private_data;
u32 old_mask, new_mask;
+ unsigned long flags;

+ spin_lock_irqsave(&irq_mask_lock, flags);
old_mask = hpriv->main_irq_mask;
new_mask = (old_mask & ~disable_bits) | enable_bits;
if (new_mask != old_mask) {
hpriv->main_irq_mask = new_mask;
mv_write_main_irq_mask(new_mask, hpriv);
}
+ spin_unlock_irqrestore(&irq_mask_lock, flags);
}

static void mv_enable_port_irqs(struct ata_port *ap,
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