[Xen-changelog] [xen master] common: make hypercall preemption checks consistent

[patchbot@xxxxxxx]

commit 8c0eed2cc8d8a2ccccdffe4c386b625b672dc12a
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Mar 13 14:26:35 2014 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Mar 13 14:26:35 2014 +0100

    common: make hypercall preemption checks consistent
    
    - never preempt on the first iteration (ensure forward progress)
    - do cheap checks first
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Tim Deegan <tim@xxxxxxx>
    Acked-by: Keir Fraser <keir@xxxxxxx>
---
 xen/common/memory.c        |    9 +++++----
 xen/common/multicall.c     |    2 +-
 xen/drivers/char/console.c |    4 ++--
 3 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/xen/common/memory.c b/xen/common/memory.c
index 9d0d32e..4d6ffee 100644
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -63,7 +63,7 @@ static void increase_reservation(struct memop_args *a)
 
     for ( i = a->nr_done; i < a->nr_extents; i++ )
     {
-        if ( hypercall_preempt_check() )
+        if ( i != a->nr_done && hypercall_preempt_check() )
         {
             a->preempted = 1;
             goto out;
@@ -109,7 +109,7 @@ static void populate_physmap(struct memop_args *a)
 
     for ( i = a->nr_done; i < a->nr_extents; i++ )
     {
-        if ( hypercall_preempt_check() )
+        if ( i != a->nr_done && hypercall_preempt_check() )
         {
             a->preempted = 1;
             goto out;
@@ -268,7 +268,7 @@ static void decrease_reservation(struct memop_args *a)
 
     for ( i = a->nr_done; i < a->nr_extents; i++ )
     {
-        if ( hypercall_preempt_check() && i != a->nr_done )
+        if ( i != a->nr_done && hypercall_preempt_check() )
         {
             a->preempted = 1;
             goto out;
@@ -398,7 +398,8 @@ static long 
memory_exchange(XEN_GUEST_HANDLE_PARAM(xen_memory_exchange_t) arg)
           i < (exch.in.nr_extents >> in_chunk_order);
           i++ )
     {
-        if ( hypercall_preempt_check() )
+        if ( i != (exch.nr_exchanged >> in_chunk_order) &&
+             hypercall_preempt_check() )
         {
             exch.nr_exchanged = i << in_chunk_order;
             rcu_unlock_domain(d);
diff --git a/xen/common/multicall.c b/xen/common/multicall.c
index 2afba98..e66c798 100644
--- a/xen/common/multicall.c
+++ b/xen/common/multicall.c
@@ -52,7 +52,7 @@ do_multicall(
 
     for ( i = 0; !rc && i < nr_calls; i++ )
     {
-        if ( hypercall_preempt_check() )
+        if ( i && hypercall_preempt_check() )
             goto preempted;
 
         if ( unlikely(__copy_from_guest(&mcs->call, call_list, 1)) )
diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index 7d4383c..beda79f 100644
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -375,12 +375,12 @@ static 
DECLARE_SOFTIRQ_TASKLET(notify_dom0_con_ring_tasklet,
 static long guest_console_write(XEN_GUEST_HANDLE_PARAM(char) buffer, int count)
 {
     char kbuf[128];
-    int kcount;
+    int kcount = 0;
     struct domain *cd = current->domain;
 
     while ( count > 0 )
     {
-        if ( hypercall_preempt_check() )
+        if ( kcount && hypercall_preempt_check() )
             return hypercall_create_continuation(
                 __HYPERVISOR_console_io, "iih",
                 CONSOLEIO_write, count, buffer);
--
generated by git-patchbot for /home/xen/git/xen.git#master

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