[PATCH 1/2] drivers: acpi: fix typo in ACPI_DECLARE_PROBE_ENTRY macro

[PATCH 1/2] drivers: acpi: fix typo in ACPI_DECLARE_PROBE_ENTRY macro

[Lorenzo Pieralisi]

When the ACPI_DECLARE_PROBE_ENTRY macro was added in
commit e647b532275b ("ACPI: Add early device probing infrastructure"),
a stub macro adding an unused entry was added for the !CONFIG_ACPI
Kconfig option case to make sure kernel code making use of the
macro did not require to be guarded within CONFIG_ACPI in order to
be compiled.

The stub macro was never used since all kernel code that defines
ACPI_DECLARE_PROBE_ENTRY entries is currently guarded within
CONFIG_ACPI; it contains a typo that should be nonetheless fixed.

Fix the typo in the stub (ie !CONFIG_ACPI) ACPI_DECLARE_PROBE_ENTRY()
macro so that it can actually be used if needed.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Fixes: e647b532275b ("ACPI: Add early device probing infrastructure")
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Marc Zyngier <Marc.Zyngier@arm.com>
---
 include/linux/acpi.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 4d8452c..c5eaf2f 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -1056,7 +1056,7 @@ static inline struct fwnode_handle *acpi_get_next_subnode(struct device *dev,
 	return NULL;
 }
 
-#define ACPI_DECLARE_PROBE_ENTRY(table, name, table_id, subtable, validate, data, fn) \
+#define ACPI_DECLARE_PROBE_ENTRY(table, name, table_id, subtable, valid, data, fn) \
 	static const void * __acpi_table_##name[]			\
 		__attribute__((unused))					\
 		 = { (void *) table_id,					\
-- 
2.6.4

[PATCH 2/2] drivers: acpi: replace acpi_probe_lock spinlock with mutex

[Lorenzo Pieralisi]

Commit e647b532275b ("ACPI: Add early device probing infrastructure")
introduced code that allows inserting driver specific
struct acpi_probe_entry probe entries into acpi linker sections
(one per-subsystem, eg irqchip, clocksource) that are then walked
to retrieve the data and function hooks required to probe the
respective kernel components.

Probing for all entries in a section is triggered through
the __acpi_probe_device_table() function, that in turn, according
to the table id a given probe entry reports parses the table
with the function retrieved from the respective section structures
(ie struct acpi_probe_entry). Owing to the current ACPI table
parsing implementation, the __acpi_probe_device_table() function
has to share global variables with the acpi_match_madt() function, so
in order to guarantee mutual exclusion locking is required
between the two functions.

Current kernel code implements the locking through the acpi_probe_lock
spinlock; this has the side effect of requiring all code called
within the lock (ie struct acpi_probe_entry.probe_{table/subtbl} hooks)
not to sleep.

However, kernel subsystems that make use of the early probing
infrastructure, are relying on kernel APIs that may sleep (eg
irq_domain_alloc_fwnode(), among others) in the function calls
pointed at by struct acpi_probe_entry.{probe_table/subtbl} entries
(eg gic_v2_acpi_init()), which is a bug.

Since __acpi_probe_device_table() is called from context
that is allowed to sleep the acpi_probe_lock spinlock can be replaced
with a mutex; this fixes the issue whilst still guaranteeing
mutual exclusion.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Fixes: e647b532275b ("ACPI: Add early device probing infrastructure")
Cc: Tomasz Nowicki <tn@semihalf.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Marc Zyngier <marc.zyngier@arm.com>
---
 drivers/acpi/scan.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index ad9fc84..e878fc7 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -2054,7 +2054,7 @@ int __init acpi_scan_init(void)
 
 static struct acpi_probe_entry *ape;
 static int acpi_probe_count;
-static DEFINE_SPINLOCK(acpi_probe_lock);
+static DEFINE_MUTEX(acpi_probe_mutex);
 
 static int __init acpi_match_madt(struct acpi_subtable_header *header,
 				  const unsigned long end)
@@ -2073,7 +2073,7 @@ int __init __acpi_probe_device_table(struct acpi_probe_entry *ap_head, int nr)
 	if (acpi_disabled)
 		return 0;
 
-	spin_lock(&acpi_probe_lock);
+	mutex_lock(&acpi_probe_mutex);
 	for (ape = ap_head; nr; ape++, nr--) {
 		if (ACPI_COMPARE_NAME(ACPI_SIG_MADT, ape->id)) {
 			acpi_probe_count = 0;
@@ -2086,7 +2086,7 @@ int __init __acpi_probe_device_table(struct acpi_probe_entry *ap_head, int nr)
 				count++;
 		}
 	}
-	spin_unlock(&acpi_probe_lock);
+	mutex_unlock(&acpi_probe_mutex);
 
 	return count;
 }
-- 
2.6.4