Re: [Patch v2] sysfs: add lockdep class support to s_active

[Cong Wang]

Eric W. Biederman wrote:
> Amerigo Wang <amwang@xxxxxxxxxx> writes:
>
> > Recently we met a lockdep warning from sysfs during s2ram or cpu hotplug.
> > As reported by several people, it is something like:
> >
> > [ 6967.926563] ACPI: Preparing to enter system sleep state S3
> > [ 6967.956156] Disabling non-boot CPUs ...
> > [ 6967.970401]
> > [ 6967.970408] =============================================
> > [ 6967.970419] [ INFO: possible recursive locking detected ]
> > [ 6967.970431] 2.6.33-rc2-git6 #27
> > [ 6967.970439] ---------------------------------------------
> > [ 6967.970450] pm-suspend/22147 is trying to acquire lock:
> > [ 6967.970460]  (s_active){++++.+}, at: [<c10d2941>]
> > sysfs_hash_and_remove+0x3d/0x4f
> > [ 6967.970493]
> > [ 6967.970497] but task is already holding lock:
> > [ 6967.970506]  (s_active){++++.+}, at: [<c10d4110>]
> > sysfs_get_active_two+0x16/0x36
> > [...]
> >
> > Eric already provides a patch for this[1], but it still can't fix the
> > problem. Based on his work and Peter's suggestion, I write this patch,
> > hopefully we can fix the warning completely.
> >
> > This patch put sysfs s_active into two classes, one is for PM, the other
> > is for the rest, so lockdep will distinguish them.
> >
> > 1. http://lkml.org/lkml/2010/1/10/282
>
> What testing has this patch seen?
>
> In particular does this work to actually clear up the pm case?

Sorry, it seems that my machine doesn't support s2ram, I am still
trying to make it working...

I hope the reporters of this bug can help to test this patch.

Thanks.
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