linux-kernel - Re: [PATCH] ACPI: fix acpi_power

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Date:	Sun, 3 Jul 2011 10:35:32 +0200
From:	Andrea Righi <andrea@...terlinux.com>
To:	Florian Mickler <florian@...kler.org>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>, Len Brown <lenb@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Maciej Rutecki <maciej.rutecki@...il.com>,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ACPI: fix acpi_power_off lockdep splat

On Sun, Jul 03, 2011 at 10:21:37AM +0200, Florian Mickler wrote:
> On Sun, 3 Jul 2011 08:58:41 +0200
> "Rafael J. Wysocki" <rjw@...k.pl> wrote:
> 
> > On Saturday, July 02, 2011, Andrea Righi wrote:
> > > Implement acpi_os_create_lock() as a C-preprocessor macro to assign
> > > unique lock_class_key to dynamically allocated locks and suppress wrong
> > > lockdep warnings.
> > > 
> > > This fixes:
> > > https://bugzilla.kernel.org/show_bug.cgi?id=38152
> > > 
> > > Reported-by: Borislav Petkov <bp@...en8.de>
> > > Signed-off-by: Andrea Righi <andrea@...terlinux.com>
> > 
> > So, how exactly does it work?
> 
> The spin_lock_init macro stringifies it's argument and uses that as a
> name for the lock in the debugging.

Correct.

> 
> By re-executing spin_lock_init (have not checked if that harms
> anything, but it should be ok) in the _macro_ the key changes from
> "lock" for all three locks to the actual argument
> "&acpi_gbl_global_lock_pending_lock", "&acpi_gbl_gpe_lock" or
> "&acpi_gbl_hardware_lock". 

We can simply move spin_lock_init() out of __acpi_os_create_lock(), so
that we have a single spin_lock_init() in the acpi_os_create_lock macro.

I'll post another patch soon (and I'll also add your description on
how it works).

Thanks!
-Andrea

> 
> Regards,
> Flo
> 
> > > ---
> > >  drivers/acpi/osl.c      |    2 +-
> > >  include/acpi/acpiosxf.h |   12 +++++++++++-
> > >  2 files changed, 12 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
> > > index 52ca964..2a67602 100644
> > > --- a/drivers/acpi/osl.c
> > > +++ b/drivers/acpi/osl.c
> > > @@ -1336,7 +1336,7 @@ EXPORT_SYMBOL(acpi_resources_are_enforced);
> > >   * Create and initialize a spinlock.
> > >   */
> > >  acpi_status
> > > -acpi_os_create_lock(acpi_spinlock *out_handle)
> > > +__acpi_os_create_lock(acpi_spinlock *out_handle)
> > >  {
> > >  	spinlock_t *lock;
> > >  
> > > diff --git a/include/acpi/acpiosxf.h b/include/acpi/acpiosxf.h
> > > index a756bc8..4a0385d 100644
> > > --- a/include/acpi/acpiosxf.h
> > > +++ b/include/acpi/acpiosxf.h
> > > @@ -99,7 +99,17 @@ acpi_os_table_override(struct acpi_table_header *existing_table,
> > >   * Spinlock primitives
> > >   */
> > >  acpi_status
> > > -acpi_os_create_lock(acpi_spinlock *out_handle);
> > > +__acpi_os_create_lock(acpi_spinlock *out_handle);
> > > +
> > > +#define acpi_os_create_lock(__handle)			\
> > > +({							\
> > > +	acpi_status ret;				\
> > > +							\
> > > +	ret = __acpi_os_create_lock(__handle);		\
> > > +	if (ret == AE_OK)				\
> > > +		spin_lock_init(*(__handle));		\
> > 
> > It seems that spin_lock_init() has already been done on *__handle, right?
> > 
> > > +	ret;						\
> > > +})
> > >  
> > >  void acpi_os_delete_lock(acpi_spinlock handle);
> > 
> > Rafael
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