Re: Bug report and patch about IRQ freezing after gic_restore_state

[Ian Campbell <Ian.Campbell@citrix.com>]

On Wed, 2013-05-22 at 17:55 +0100, Stefano Stabellini wrote:
> On Wed, 22 May 2013, Jaeyong Yoo wrote:
> > I got it.
> > Here goes the updated patch:

Please can you include the (updated as necessary) changelog when
reposting variants on patches. I have written one for you this time.

> > 
> > Signed-off-by: Jaeyong Yoo <jaeyong.yoo@samsung.com>
> 
> Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

I applied this but I had to workaround the fact that the patch had DOS
line endings.

Jaeyong, please can you try and fix this for next time.

The wiki page http://wiki.xen.org/wiki/Submitting_Xen_Patches might help
with some advice for tooling, in particular it has advice on using git
as well as a link to
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=Documentation/email-clients.txt;hb=HEAD which has lots of useful advice on convincing your MUA not to mangle things...

What I have committed is below, please check that it is correct.

Cheers,
Ian.

commit 9f5179a4ecafd9a15e0a066e0f935ded681bf997
Author: Jaeyong Yoo <jaeyong.yoo@samsung.com>
Date:   Wed May 22 02:34:18 2013 +0000

    xen/arm: Disable interrupts for the entire duration of the context switch
    
    Not just while saving state. Otherwise there is a race between interrupts
    arriving and updating the LR state and gic_restore_state overwriting them with
    the saved state.
    
    With this change we no longer need to disable interrupts in gic_restore_state.
    
    Signed-off-by: Jaeyong Yoo <jaeyong.yoo@samsung.com>
    Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
    [ ijc -- rewrote commit message ]

diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
index 9ca44ea..ee12b5f 100644
--- a/xen/arch/arm/domain.c
+++ b/xen/arch/arm/domain.c
@@ -226,10 +226,10 @@ static void schedule_tail(struct vcpu *prev)
 {
     ctxt_switch_from(prev);
 
-    local_irq_enable();
-
     ctxt_switch_to(current);
 
+    local_irq_enable();
+
     if ( prev != current )
         update_runstate_area(current);
 }
diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
index 30bf8d1..d9940ea 100644
--- a/xen/arch/arm/gic.c
+++ b/xen/arch/arm/gic.c
@@ -93,11 +93,9 @@ void gic_restore_state(struct vcpu *v)
     if ( is_idle_vcpu(v) )
         return;
 
-    spin_lock_irq(&gic.lock);
     this_cpu(lr_mask) = v->arch.lr_mask;
     for ( i=0; i<nr_lrs; i++)
         GICH[GICH_LR + i] = v->arch.gic_lr[i];
-    spin_unlock_irq(&gic.lock);
     GICH[GICH_APR] = v->arch.gic_apr;
     GICH[GICH_HCR] = GICH_HCR_EN;
     isb();