ACPI: Avoid calling request_irq() many times for the same interrupt

In principle acpi_os_install_interrupt_handler() may be called
multiple times for different interrupts, either from
acpi_ev_get_gpe_xrupt_block(), or from acpi_ev_install_sci_handler().
However, it always attempts to request the same interrupt,
acpi_gbl_FADT.sci_interrupt and it doesn't check whether or not this
interrupt has already been requested.

Modify this function so that it refuses to request interrupts other
than acpi_gbl_FADT.sci_interrupt and change
acpi_os_remove_interrupt_handler() so that it refuses to free such
interrupts.  Use the observation that the only supported ACPI
interrupt must be equal to acpi_gbl_FADT.sci_interrupt and drop an
unnecessary variable acpi_irq_irq.

This change has been tested on Toshiba Portege R500 and HP nx6325
without introducing any visible problems.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

drivers/acpi/osl.c

@@ -76,7 +76,6 @@ EXPORT_SYMBOL(acpi_in_debugger);
 extern char line_buf[80];
 #endif				/*ENABLE_DEBUGGER */
 
-static unsigned int acpi_irq_irq;
 static acpi_osd_handler acpi_irq_handler;
 static void *acpi_irq_context;
 static struct workqueue_struct *kacpid_wq;
@@ -516,11 +515,15 @@ acpi_os_install_interrupt_handler(u32 gsi, acpi_osd_handler handler,
 	acpi_irq_stats_init();
 
 	/*
-	 * Ignore the GSI from the core, and use the value in our copy of the
-	 * FADT. It may not be the same if an interrupt source override exists
-	 * for the SCI.
+	 * ACPI interrupts different from the SCI in our copy of the FADT are
+	 * not supported.
 	 */
-	gsi = acpi_gbl_FADT.sci_interrupt;
+	if (gsi != acpi_gbl_FADT.sci_interrupt)
+		return AE_BAD_PARAMETER;
+
+	if (acpi_irq_handler)
+		return AE_ALREADY_ACQUIRED;
+
 	if (acpi_gsi_to_irq(gsi, &irq) < 0) {
 		printk(KERN_ERR PREFIX "SCI (ACPI GSI %d) not registered\n",
 		       gsi);
@@ -531,20 +534,20 @@ acpi_os_install_interrupt_handler(u32 gsi, acpi_osd_handler handler,
 	acpi_irq_context = context;
 	if (request_irq(irq, acpi_irq, IRQF_SHARED, "acpi", acpi_irq)) {
 		printk(KERN_ERR PREFIX "SCI (IRQ%d) allocation failed\n", irq);
+		acpi_irq_handler = NULL;
 		return AE_NOT_ACQUIRED;
 	}
-	acpi_irq_irq = irq;
 
 	return AE_OK;
 }
 
 acpi_status acpi_os_remove_interrupt_handler(u32 irq, acpi_osd_handler handler)
 {
-	if (irq) {
-		free_irq(irq, acpi_irq);
-		acpi_irq_handler = NULL;
-		acpi_irq_irq = 0;
-	}
+	if (irq != acpi_gbl_FADT.sci_interrupt)
+		return AE_BAD_PARAMETER;
+
+	free_irq(irq, acpi_irq);
+	acpi_irq_handler = NULL;
 
 	return AE_OK;
 }
@@ -1603,7 +1606,7 @@ acpi_status __init acpi_os_initialize1(void)
 acpi_status acpi_os_terminate(void)
 {
 	if (acpi_irq_handler) {
-		acpi_os_remove_interrupt_handler(acpi_irq_irq,
+		acpi_os_remove_interrupt_handler(acpi_gbl_FADT.sci_interrupt,
 						 acpi_irq_handler);
 	}