Add down_timeout and change ACPI to use it
ACPI currently emulates a timeout for semaphores with calls to
down_trylock and sleep. This produces horrible behaviour in terms of
fairness and excessive wakeups. Now that we have a unified semaphore
implementation, adding a real down_trylock is almost trivial.
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index a697fb6..a498a6c 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -4,6 +4,8 @@
* Copyright (C) 2000 Andrew Henroid
* Copyright (C) 2001, 2002 Andy Grover <andrew.grover@intel.com>
* Copyright (C) 2001, 2002 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
+ * Copyright (c) 2008 Intel Corporation
+ * Author: Matthew Wilcox <willy@linux.intel.com>
*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
@@ -37,15 +39,18 @@
#include <linux/workqueue.h>
#include <linux/nmi.h>
#include <linux/acpi.h>
-#include <acpi/acpi.h>
-#include <asm/io.h>
-#include <acpi/acpi_bus.h>
-#include <acpi/processor.h>
-#include <asm/uaccess.h>
-
#include <linux/efi.h>
#include <linux/ioport.h>
#include <linux/list.h>
+#include <linux/jiffies.h>
+#include <linux/semaphore.h>
+
+#include <asm/io.h>
+#include <asm/uaccess.h>
+
+#include <acpi/acpi.h>
+#include <acpi/acpi_bus.h>
+#include <acpi/processor.h>
#define _COMPONENT ACPI_OS_SERVICES
ACPI_MODULE_NAME("osl");
@@ -764,7 +769,6 @@
{
struct semaphore *sem = NULL;
-
sem = acpi_os_allocate(sizeof(struct semaphore));
if (!sem)
return AE_NO_MEMORY;
@@ -791,12 +795,12 @@
{
struct semaphore *sem = (struct semaphore *)handle;
-
if (!sem)
return AE_BAD_PARAMETER;
ACPI_DEBUG_PRINT((ACPI_DB_MUTEX, "Deleting semaphore[%p].\n", handle));
+ BUG_ON(!list_empty(&sem->wait_list));
kfree(sem);
sem = NULL;
@@ -804,21 +808,15 @@
}
/*
- * TODO: The kernel doesn't have a 'down_timeout' function -- had to
- * improvise. The process is to sleep for one scheduler quantum
- * until the semaphore becomes available. Downside is that this
- * may result in starvation for timeout-based waits when there's
- * lots of semaphore activity.
- *
* TODO: Support for units > 1?
*/
acpi_status acpi_os_wait_semaphore(acpi_handle handle, u32 units, u16 timeout)
{
acpi_status status = AE_OK;
struct semaphore *sem = (struct semaphore *)handle;
+ long jiffies;
int ret = 0;
-
if (!sem || (units < 1))
return AE_BAD_PARAMETER;
@@ -828,58 +826,14 @@
ACPI_DEBUG_PRINT((ACPI_DB_MUTEX, "Waiting for semaphore[%p|%d|%d]\n",
handle, units, timeout));
- /*
- * This can be called during resume with interrupts off.
- * Like boot-time, we should be single threaded and will
- * always get the lock if we try -- timeout or not.
- * If this doesn't succeed, then we will oops courtesy of
- * might_sleep() in down().
- */
- if (!down_trylock(sem))
- return AE_OK;
-
- switch (timeout) {
- /*
- * No Wait:
- * --------
- * A zero timeout value indicates that we shouldn't wait - just
- * acquire the semaphore if available otherwise return AE_TIME
- * (a.k.a. 'would block').
- */
- case 0:
- if (down_trylock(sem))
- status = AE_TIME;
- break;
-
- /*
- * Wait Indefinitely:
- * ------------------
- */
- case ACPI_WAIT_FOREVER:
- down(sem);
- break;
-
- /*
- * Wait w/ Timeout:
- * ----------------
- */
- default:
- // TODO: A better timeout algorithm?
- {
- int i = 0;
- static const int quantum_ms = 1000 / HZ;
-
- ret = down_trylock(sem);
- for (i = timeout; (i > 0 && ret != 0); i -= quantum_ms) {
- schedule_timeout_interruptible(1);
- ret = down_trylock(sem);
- }
-
- if (ret != 0)
- status = AE_TIME;
- }
- break;
- }
+ if (timeout == ACPI_WAIT_FOREVER)
+ jiffies = MAX_SCHEDULE_TIMEOUT;
+ else
+ jiffies = msecs_to_jiffies(timeout);
+
+ ret = down_timeout(sem, jiffies);
+ if (ret)
+ status = AE_TIME;
if (ACPI_FAILURE(status)) {
ACPI_DEBUG_PRINT((ACPI_DB_MUTEX,
@@ -902,7 +856,6 @@
{
struct semaphore *sem = (struct semaphore *)handle;
-
if (!sem || (units < 1))
return AE_BAD_PARAMETER;