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Date: Mon, 4 Jul 2011 00:28:23 +0200
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Andrea Righi <andrea@...terlinux.com>
Cc: 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>,
Florian Mickler <florian@...kler.org>,
linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] ACPI: fix acpi_power_off lockdep splat
On Monday, July 04, 2011, Rafael J. Wysocki wrote:
> On Sunday, July 03, 2011, Rafael J. Wysocki wrote:
> > On Sunday, July 03, 2011, Andrea Righi wrote:
> > > Implement acpi_os_create_lock() as a C-preprocessor macro to suppress
> > > lockdep false positive.
> > >
> > > When lockdep is enabled the spin_lock_init macro stringifies it's
> > > argument and uses that as a name for the lock in the debugging.
> > >
> > > By executing spin_lock_init in a macro the key changes from "lock" for
> > > all locks to the actual argument of acpi_os_create_lock()
> > > ("&acpi_gbl_global_lock_pending_lock", "&acpi_gbl_gpe_lock" or
> > > "&acpi_gbl_hardware_lock" for now).
> > >
> > > This fixes:
> > > https://bugzilla.kernel.org/show_bug.cgi?id=38152
> > >
> > > ChangeLog (v1 -> v2):
> > > - avoid to call spin_lock_init multiple times on the same lock
> > > - rewrite patch description (thanks to Florian for providing a better
> > > description of the patch)
> > >
> > > Reported-by: Borislav Petkov <bp@...en8.de>
> > > CC: Florian Mickler <florian@...kler.org>
> > > Signed-off-by: Andrea Righi <andrea@...terlinux.com>
> > > ---
> > > drivers/acpi/osl.c | 3 +--
> > > include/acpi/acpiosxf.h | 12 +++++++++++-
> > > 2 files changed, 12 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
> > > index 52ca964..4c985d3 100644
> > > --- a/drivers/acpi/osl.c
> > > +++ b/drivers/acpi/osl.c
> > > @@ -1336,14 +1336,13 @@ 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)
> > > {
> >
> > I would rename this to acpi_os_allocate_lock() or acpi_os_alloc_lock(),
> > so that it doesn't suggest the lock is initialized by this function.
> >
> > Hmm. There's one more thing we need to take into account here. Namely,
> > include/acpi/acpiosxf.h is used by other OSes, so we shouldn't put
> > Linux-specific stuff into it.
> >
> > I'm not sure how to work around that at the moment.
>
> OK, the patch below builds for me and seems to work even, although I haven't
> tested it with lockdep on.
Below is a cleaned-up version, still untested with lockdep on.
Thanks,
Rafael
---
drivers/acpi/osl.c | 17 -----------------
include/acpi/acpiosxf.h | 3 +++
include/acpi/platform/aclinux.h | 18 ++++++++++++++++++
3 files changed, 21 insertions(+), 17 deletions(-)
Index: linux-2.6/drivers/acpi/osl.c
===================================================================
--- linux-2.6.orig/drivers/acpi/osl.c
+++ linux-2.6/drivers/acpi/osl.c
@@ -1333,23 +1333,6 @@ int acpi_resources_are_enforced(void)
EXPORT_SYMBOL(acpi_resources_are_enforced);
/*
- * Create and initialize a spinlock.
- */
-acpi_status
-acpi_os_create_lock(acpi_spinlock *out_handle)
-{
- spinlock_t *lock;
-
- lock = ACPI_ALLOCATE(sizeof(spinlock_t));
- if (!lock)
- return AE_NO_MEMORY;
- spin_lock_init(lock);
- *out_handle = lock;
-
- return AE_OK;
-}
-
-/*
* Deallocate the memory for a spinlock.
*/
void acpi_os_delete_lock(acpi_spinlock handle)
Index: linux-2.6/include/acpi/acpiosxf.h
===================================================================
--- linux-2.6.orig/include/acpi/acpiosxf.h
+++ linux-2.6/include/acpi/acpiosxf.h
@@ -98,8 +98,11 @@ acpi_os_table_override(struct acpi_table
/*
* Spinlock primitives
*/
+
+#ifndef acpi_os_create_lock
acpi_status
acpi_os_create_lock(acpi_spinlock *out_handle);
+#endif
void acpi_os_delete_lock(acpi_spinlock handle);
Index: linux-2.6/include/acpi/platform/aclinux.h
===================================================================
--- linux-2.6.orig/include/acpi/platform/aclinux.h
+++ linux-2.6/include/acpi/platform/aclinux.h
@@ -159,6 +159,24 @@ static inline void *acpi_os_acquire_obje
} while (0)
#endif
+/*
+ * When lockdep is enabled, the spin_lock_init() macro stringifies it's
+ * argument and uses that as a name for the lock in debugging.
+ * By executing spin_lock_init() in a macro the key changes from "lock" for
+ * all locks to the name of the argument of acpi_os_create_lock(), which
+ * prevents lockdep from reporting false positives for ACPICA locks.
+ */
+#define acpi_os_create_lock(__handle) \
+({ \
+ spinlock_t *lock = ACPI_ALLOCATE(sizeof(*lock)); \
+ \
+ if (lock) { \
+ *(__handle) = lock; \
+ spin_lock_init(*(__handle)); \
+ } \
+ lock ? AE_OK : AE_NO_MEMORY; \
+})
+
#endif /* __KERNEL__ */
#endif /* __ACLINUX_H__ */
--
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