genirq: Remove IRQF_DISABLED from core code

Remove all code which is related to IRQF_DISABLED from the core kernel
code. IRQF_DISABLED still exists as a flag, but becomes a NOOP and
will be removed after a grace period. That way we can easily revert to
the previous behaviour by just restoring the core code.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Miller <davem@davemloft.net>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Linus Torvalds <torvalds@osdl.org>
LKML-Reference: <20100326000405.991244690@linutronix.de>

Documentation/feature-removal-schedule.txt

@@ -589,3 +589,10 @@ Why:	Useful in 2003, implementation is a hack.
 	Generally invoked by accident today.
 	Seen as doing more harm than good.
 Who:	Len Brown <len.brown@intel.com>
+
+----------------------------
+
+What:	IRQF_DISABLED
+When:	2.6.36
+Why:	The flag is a NOOP as we run interrupt handlers with interrupts disabled
+Who:	Thomas Gleixner <tglx@linutronix.de>

include/linux/interrupt.h

@@ -39,7 +39,8 @@
  * These flags used only by the kernel as part of the
  * irq handling routines.
  *
- * IRQF_DISABLED - keep irqs disabled when calling the action handler
+ * IRQF_DISABLED - keep irqs disabled when calling the action handler.
+ *                 DEPRECATED. This flag is a NOOP and scheduled to be removed
  * IRQF_SAMPLE_RANDOM - irq is used to feed the random generator
  * IRQF_SHARED - allow sharing the irq among several devices
  * IRQF_PROBE_SHARED - set by callers when they expect sharing mismatches to occur

kernel/irq/manage.c

@@ -757,16 +757,6 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
 		if (new->flags & IRQF_ONESHOT)
 			desc->status |= IRQ_ONESHOT;
 
-		/*
-		 * Force MSI interrupts to run with interrupts
-		 * disabled. The multi vector cards can cause stack
-		 * overflows due to nested interrupts when enough of
-		 * them are directed to a core and fire at the same
-		 * time.
-		 */
-		if (desc->msi_desc)
-			new->flags |= IRQF_DISABLED;
-
 		if (!(desc->status & IRQ_NOAUTOEN)) {
 			desc->depth = 0;
 			desc->status &= ~IRQ_DISABLED;
@@ -1027,7 +1017,6 @@ EXPORT_SYMBOL(free_irq);
  *	Flags:
  *
  *	IRQF_SHARED		Interrupt is shared
- *	IRQF_DISABLED	Disable local interrupts while processing
  *	IRQF_SAMPLE_RANDOM	The interrupt can be used for entropy
  *	IRQF_TRIGGER_*		Specify active edge(s) or level
  *
@@ -1040,25 +1029,6 @@ int request_threaded_irq(unsigned int irq, irq_handler_t handler,
 	struct irq_desc *desc;
 	int retval;
 
-	/*
-	 * handle_IRQ_event() always ignores IRQF_DISABLED except for
-	 * the _first_ irqaction (sigh).  That can cause oopsing, but
-	 * the behavior is classified as "will not fix" so we need to
-	 * start nudging drivers away from using that idiom.
-	 */
-	if ((irqflags & (IRQF_SHARED|IRQF_DISABLED)) ==
-					(IRQF_SHARED|IRQF_DISABLED)) {
-		pr_warning(
-		  "IRQ %d/%s: IRQF_DISABLED is not guaranteed on shared IRQs\n",
-			irq, devname);
-	}
-
-#ifdef CONFIG_LOCKDEP
-	/*
-	 * Lockdep wants atomic interrupt handlers:
-	 */
-	irqflags |= IRQF_DISABLED;
-#endif
 	/*
 	 * Sanity-check: shared interrupts must pass in a real dev-ID,
 	 * otherwise we'll have trouble later trying to figure out