diff mbox series

[3/4] x86/IRQ: relax locking in irq_guest_eoi_timer_fn()

Message ID 5CD2CFE6020000780022CCC9@prv1-mh.provo.novell.com (mailing list archive)
State New, archived
Headers show
Series x86: EOI timer corrections / improvements | expand

Commit Message

Jan Beulich May 8, 2019, 12:47 p.m. UTC 
This is a timer handler, so it gets entered with IRQs enabled. Therefore
there's no need to save/restore the IRQ masking flag.

Additionally the final switch()'es ACKTYPE_EOI case re-acquires the lock
just for it to be dropped again right away. Do away with this.

Signed-off-by: Jan Beulich <jbeulich@suse.com>

Comments

Roger Pau Monné May 16, 2019, 1:48 p.m. UTC | #1 
On Wed, May 08, 2019 at 06:47:34AM -0600, Jan Beulich wrote:
> This is a timer handler, so it gets entered with IRQs enabled. Therefore
> there's no need to save/restore the IRQ masking flag.
> 
> Additionally the final switch()'es ACKTYPE_EOI case re-acquires the lock
> just for it to be dropped again right away. Do away with this.
> 
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>

Thanks.
Andrew Cooper June 5, 2019, 5:16 p.m. UTC | #2 
On 08/05/2019 13:47, Jan Beulich wrote:
> This is a timer handler, so it gets entered with IRQs enabled. Therefore
> there's no need to save/restore the IRQ masking flag.
>
> Additionally the final switch()'es ACKTYPE_EOI case re-acquires the lock
> just for it to be dropped again right away. Do away with this.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Yes - that is rather silly.

Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
diff mbox series

Patch

--- a/xen/arch/x86/irq.c
+++ b/xen/arch/x86/irq.c
@@ -1106,9 +1106,8 @@  static void irq_guest_eoi_timer_fn(void
     unsigned int irq = desc - irq_desc;
     irq_guest_action_t *action;
     cpumask_t cpu_eoi_map;
-    unsigned long flags;
 
-    spin_lock_irqsave(&desc->lock, flags);
+    spin_lock_irq(&desc->lock);
     
     if ( !(desc->status & IRQ_GUEST) )
         goto out;
@@ -1145,12 +1144,11 @@  static void irq_guest_eoi_timer_fn(void
         cpumask_copy(&cpu_eoi_map, action->cpu_eoi_map);
         spin_unlock_irq(&desc->lock);
         on_selected_cpus(&cpu_eoi_map, set_eoi_ready, desc, 0);
-        spin_lock_irq(&desc->lock);
-        break;
+        return;
     }
 
  out:
-    spin_unlock_irqrestore(&desc->lock, flags);
+    spin_unlock_irq(&desc->lock);
 }
 
 static void __do_IRQ_guest(int irq)