[PATCH] uml: Simplify console opening/closing and irq registration

This patch simplifies the opening and closing of host console devices and the
registration and deregistration of IRQs.  The intent is to make it obvious
that an IRQ can't exist without an open file descriptor.

chan_enable will now open the channel, and when both opening and IRQ
registration are desired, this should be used.  Opening only is done for the
initial console, so that interface still needs to exist.

The free_irqs_later interface is now gone.  It was intended to avoid freeing
an IRQ while it was being processed.  It did this, but it didn't eliminate the
possiblity of free_irq being called from an interrupt, which is bad.  In its
place is a list of irqs to be freed, which is processed by the signal handler
just before exiting.  close_one_chan now disables irqs.

When a host device disappears, it is just closed, and that disables IRQs.

The device id registered with the IRQ is now the chan structure, not the tty.
This is because the interrupt arrives on a descriptor associated with the
channel.  This caused equivalent changes in the arguments to line_timer_cb.
line_disable is gone since it is not used any more.

The count field in the line structure is gone.  tty->count is used instead.

The complicated logic in sigio_handler with freeing IRQs when necessary and
making sure its idea of the next irq is correct is now much simpler.  The irq
list can't be rearranged underneath it, so it is now a simple list walk.

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 7 insertions, 41 deletions

diff --git a/arch/um/kernel/irq_user.c b/arch/um/kernel/irq_user.c
index c3ccaf24f3e0..50a2aa35cda9 100644
--- a/arch/um/kernel/irq_user.c
+++ b/arch/um/kernel/irq_user.c
@@ -29,7 +29,6 @@ struct irq_fd {
         int pid;
         int events;
         int current_events;
-        int freed;
 };
 
 static struct irq_fd *active_fds = NULL;
@@ -41,9 +40,11 @@ static int pollfds_size = 0;
 
 extern int io_count, intr_count;
 
+extern void free_irqs(void);
+
 void sigio_handler(int sig, union uml_pt_regs *regs)
 {
-        struct irq_fd *irq_fd, *next;
+        struct irq_fd *irq_fd;
         int i, n;
 
         if(smp_sigio_handler()) return;
@@ -66,29 +67,15 @@ void sigio_handler(int sig, union uml_pt_regs *regs)
                         irq_fd = irq_fd->next;
                 }
 
-                for(irq_fd = active_fds; irq_fd != NULL; irq_fd = next){
-                        next = irq_fd->next;
+                for(irq_fd = active_fds; irq_fd != NULL; irq_fd = irq_fd->next){
                         if(irq_fd->current_events != 0){
                                 irq_fd->current_events = 0;
                                 do_IRQ(irq_fd->irq, regs);
-
-                                /* This is here because the next irq may be
-                                 * freed in the handler.  If a console goes
-                                 * away, both the read and write irqs will be
-                                 * freed.  After do_IRQ, ->next will point to
-                                 * a good IRQ.
-                                 * Irqs can't be freed inside their handlers,
-                                 * so the next best thing is to have them
-                                 * marked as needing freeing, so that they
-                                 * can be freed here.
-                                 */
-                                next = irq_fd->next;
-                                if(irq_fd->freed){
-                                        free_irq(irq_fd->irq, irq_fd->id);
-                                }
                         }
                 }
         }
+
+        free_irqs();
 }
 
 int activate_ipi(int fd, int pid)
@@ -136,8 +123,7 @@ int activate_fd(int irq, int fd, int type, void *dev_id)
                                      .irq               = irq,
                                      .pid               = pid,
                                      .events            = events,
-                                     .current_events    = 0,
-                                     .freed             = 0  } );
+                                     .current_events    = 0 } );
 
         /* Critical section - locked by a spinlock because this stuff can
          * be changed from interrupt handlers.  The stuff above is done 
@@ -313,26 +299,6 @@ static struct irq_fd *find_irq_by_fd(int fd, int irqnum, int *index_out)
         return(irq);
 }
 
-void free_irq_later(int irq, void *dev_id)
-{
-        struct irq_fd *irq_fd;
-        unsigned long flags;
-
-        flags = irq_lock();
-        for(irq_fd = active_fds; irq_fd != NULL; irq_fd = irq_fd->next){
-                if((irq_fd->irq == irq) && (irq_fd->id == dev_id))
-                        break;
-        }
-        if(irq_fd == NULL){
-                printk("free_irq_later found no irq, irq = %d, "
-                       "dev_id = 0x%p\n", irq, dev_id);
-                goto out;
-        }
-        irq_fd->freed = 1;
- out:
-        irq_unlock(flags);
-}
-
 void reactivate_fd(int fd, int irqnum)
 {
         struct irq_fd *irq;