linux-kernel - [Resend/Update][PATCH] ACPI: Fix lockdep false positives in acpi_power

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Message-Id: <201107062044.25387.rjw@sisk.pl>
Date:	Wed, 6 Jul 2011 20:44:25 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Len Brown <lenb@...nel.org>
Cc:	Florian Mickler <florian@...kler.org>,
	Andrea Righi <andrea@...terlinux.com>,
	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: [Resend/Update][PATCH] ACPI: Fix lockdep false positives in acpi_power_off()

From: Rafael J. Wysocki <rjw@...k.pl>
Subject: ACPI: Fix lockdep false positives in acpi_power_off()

All ACPICA locks are allocated by the same function,
acpi_os_create_lock(), with the help of a local variable called
"lock".  Thus, when lockdep is enabled, it uses "lock" as the
name of all those locks and regards them as instances of the same
lock, which causes it to report possible locking problems with them
when there aren't any.

To work around this problem, define acpi_os_create_lock() as a macro
and make it pass its argument to spin_lock_init(), so that lockdep
uses it as the name of the new lock.  Define this macron in a
Linux-specific file, to minimize the resulting modifications of
the OS-independent ACPICA parts.

This change is based on an earlier patch from Andrea Righi and it
addresses a regression from 2.6.39 tracked as
https://bugzilla.kernel.org/show_bug.cgi?id=38152

Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
Reported-and-tested-by: Borislav Petkov <bp@...en8.de>
Tested-by: Andrea Righi <andrea@...terlinux.com>
Reviewed-by: Florian Mickler <florian@...kler.org>
---
 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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