[PATCH] uml: add and use generic hw_controller_type->release

With Chris Wedgwood <cw@f00f.org>

Currently UML must explicitly call the UML-specific
free_irq_by_irq_and_dev() for each free_irq call it's done.

This is needed because ->shutdown and/or ->disable are only called when the
last "action" for that irq is removed.

Instead, for UML shared IRQs (UML IRQs are very often, if not always,
shared), for each dev_id some setup is done, which must be cleared on the
release of that fd.  For instance, for each open console a new instance
(i.e.  new dev_id) of the same IRQ is requested().

Exactly, a fd is stored in an array (pollfds), which is after read by a
host thread and passed to poll().  Each event registered by poll() triggers
an interrupt.  So, for each free_irq() we must remove the corresponding
host fd from the table, which we do via this -release() method.

In this patch we add an appropriate hook for this, and remove all uses of
it by pointing the hook to the said procedure; this is safe to do since the
said procedure.

Also some cosmetic improvements are included.

This is heavily based on some work by Chris Wedgwood, which however didn't
get the patch merged for something I'd call a "misunderstanding" (the need
for this patch wasn't cleanly explained, thus adding the generic hook was
felt as undesirable).

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
CC: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 7 insertions, 4 deletions

diff --git a/arch/um/kernel/irq.c b/arch/um/kernel/irq.c
index d44fb5282547..9f18061ef4c9 100644
--- a/arch/um/kernel/irq.c
+++ b/arch/um/kernel/irq.c
@@ -124,14 +124,16 @@ void irq_unlock(unsigned long flags)
         spin_unlock_irqrestore(&irq_spinlock, flags);
 }
 
-/*  presently hw_interrupt_type must define (startup || enable) &&
- *  disable && end */
+/* hw_interrupt_type must define (startup || enable) &&
+ * (shutdown || disable) && end */
 static void dummy(unsigned int irq)
 {
 }
 
-static struct hw_interrupt_type SIGIO_irq_type = {
+/* This is used for everything else than the timer. */
+static struct hw_interrupt_type normal_irq_type = {
         .typename = "SIGIO",
+        .release = free_irq_by_irq_and_dev,
         .disable = dummy,
         .enable = dummy,
         .ack = dummy,
@@ -140,6 +142,7 @@ static struct hw_interrupt_type SIGIO_irq_type = {
 
 static struct hw_interrupt_type SIGVTALRM_irq_type = {
         .typename = "SIGVTALRM",
+        .release = free_irq_by_irq_and_dev,
         .shutdown = dummy, /* never called */
         .disable = dummy,
         .enable = dummy,
@@ -160,7 +163,7 @@ void __init init_IRQ(void)
                 irq_desc[i].status = IRQ_DISABLED;
                 irq_desc[i].action = NULL;
                 irq_desc[i].depth = 1;
-                irq_desc[i].handler = &SIGIO_irq_type;
+                irq_desc[i].handler = &normal_irq_type;
                 enable_irq(i);
         }
 }